ENVIRONMENTAL AND HEALTH RISK ASSESSMENT OF AL-AKAIDER LANDFILL
JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
MAY, 2006
ENVIRONMENTAL AND HEALTH RISK ASSESSMENT OF AL-AKAIDER LANDFILL
By: Eng. Luay Ibrahim Qrenawi
Thesis Submitted in Partial Fulfillment of the Requirements of the Degree of Master of Science in Civil Engineering
At Faculty of Graduate Studies Jordan University of Science and Technology May, 2006
Signature of Author
Committee Members Dr. Hani Abu Qdais (Chairman) Dr. Fayez Abdulla (Co-Advisor) Dr. Munjed Al-Sharif Dr. Kamal Khdier (Cognate, MoPIC)
Signature and Date
DEDICATION
To my Parents, Brothers, Sisters and my Lovely Lovely Fiancée
I
ACKNOWLEDGEMENTS
I wish to offer my gratitude to my advisor; Dr. Hani Abu Qdais for his close supervision, advice, patience, guidance, contact, encouragement during the course of this study, and for his criticism of the manuscript. Thanks to Dr. Fayez Abdulla who was my co-advisor; I appreciate his advice, useful suggestions and comments through this work. Thanks are due to the examining committee members; Dr. Munjed Al-Sharif and Dr. Kamal Khdier for their time and sincere efforts. I would like to extend my great appreciations to all my friends expressly Tamer, Yousif, Bashar, Rami, Rasha, Mai and Maha for their support, help and encouragement. Cordial thanks are directed to the staff working at Al-Akaider landfill especially; Eng. Mohammed Khasawneh and Eng. Adnan Bsoul. My deepest thanks are directed to my parents, brothers, sisters and my lovely fiancée for their patience, guidance and support. Special thanks are directed to the German Academic Exchange Service (DAAD) for financial support.
II
TABLE OF CONTENTS Subject
Page
DEDICATION --------------------------------------------------------------------------------------------
I
ACKNOWLEDGEMENTS -----------------------------------------------------------------------------
II
TABLE OF CONTENTS --------------------------------------------------------------------------------
III
LIST OF FIGURES ---------------------------------------------------------------------------------------
VII
LIST OF TABLES ----------------------------------------------------------------------------------------
IX
LIST OF NOMENCLUTURE --------------------------------------------------------------------------
X
ABSTRACT -----------------------------------------------------------------------------------------------
XIII
CHAPTER ONE " INTRODUCTION"
1
1.1
Statement of the Problem ---------------------------------------------------------------------
1
1.2
Characteristics of Solid Waste in Jordan -----------------------------------------------------
3
1.2.1
Solid Waste Generation Rate --------------------------------------------------
3
1.2.2
Solid Waste Composition ------------------------------------------------------
4
1.2.3
Final Disposal Sites of Solid Waste ------------------------------------------
4
1.3
Landfilling Practices in Jordan ----------------------------------------------------------------
6
1.4
Objectives of the Study -------------------------------------------------------------------------
7
1.5
Overall Methodology ---------------------------------------------------------------------------
8
1.6
Thesis Organization -----------------------------------------------------------------------------
8
CHAPTER TWO "LITERATURE REVIEW"
10
2.1
Introduction --------------------------------------------------------------------------------------
10
2.2
Landfill Siting Considerations -----------------------------------------------------------------
11
2.3
Location Restrictions of Landfills ------------------------------------------------------------
13
2.4
Environmental Impacts of Landfills ----------------------------------------------------------
13
2.5
Leachate ------------------------------------------------------------------------------------------
13
2.6
Impacts of Landfill Leachate ------------------------------------------------------------------
16
2.6.1
Groundwater Contamination --------------------------------------------------
16
2.6.2
Surface Water Pollution --------------------------------------------------------
17
2.7
Reduction of the Impacts of Leachate on Groundwater ------------------------------------
18
2.8
Landfill gas ---------------------------------------------------------------------------------------
19
2.8.1
Bacterial Decomposition -------------------------------------------------------
19
2.8.1.1
Phase I --------------------------------------------------------------------
20
2.8.1.2
Phase II -------------------------------------------------------------------
20
2.8.1.3
Phase III ------------------------------------------------------------------
21
2.8.1.4
Phase IV ------------------------------------------------------------------
22
Volatilization --------------------------------------------------------------------
22
2.8.2
III
2.8.3 2.9 2.10
2.11
Chemical Reactions -------------------------------------------------------------
23
Gas Collection System -----------------------------------------------------------------------
23
Impacts of Gases Generated in Landfills -----------------------------------------------------
23
2.10.1
Health Impacts ------------------------------------------------------------------
23
2.10.2
Global Warming ----------------------------------------------------------------
24
2.10.3
Fires and Explosions ------------------------------------------------------------
25
2.10.4
Unpleasant Odors ---------------------------------------------------------------
26
2.10.5
Vegetation Damage -------------------------------------------------------------
26
2.10.6
Air Pollution ---------------------------------------------------------------------
27
2.10.7
Groundwater Contamination --------------------------------------------------
28
Other Impacts Associated with Landfills ----------------------------------------------------
28
2.11.1
Dust Problems -------------------------------------------------------------------
28
2.11.2
Vectors ---------------------------------------------------------------------------
28
2.11.3
Noise and Aesthetics -----------------------------------------------------------
29
2.11.4
Flood ------------------------------------------------------------------------------
29
2.11.5
Landfill Settlement -------------------------------------------------------------
30
2.12
Risk Assessment ---------------------------------------------------------------------------------
31
2.13
Health Risk Assessment ------------------------------------------------------------------------
32
2.14
Environmental Risk Assessment --------------------------------------------------------------
32
2.15
Risk Assessment for Waste Disposal Sites --------------------------------------------------
33
2.16
Public Perception of Waste Disposal Risk ---------------------------------------------------
33
2.17
Risk Assessment Models -----------------------------------------------------------------------
34
2.18
Steps of Risk Assessment ----------------------------------------------------------------------
34
2.19
Uncertainty of Risk Assessment --------------------------------------------------------------
35
2.20
Strengths of Environmental Risk Assessment -----------------------------------------------
35
2.21
Limitations of Environmental Risk Assessment --------------------------------------------
36
2.22
Previous Related Studies -----------------------------------------------------------------------
37
CHAPTER THREE "STUDY AREA"
41
3.1
Location and Site Description------------------------------------------------------------------
41
3.2
Climatic Conditions -----------------------------------------------------------------------------
43
3.2.1
Rainfall, Temperature and Solar Radiation ----------------------------------
43
3.2.2
Relative Humidity --------------------------------------------------------------
46
3.2.3
Wind Speed and Direction -----------------------------------------------------
47
3.3
Topography --------------------------------------------------------------------------------------
49
3.4
Hydrogeology and Soil Characteristics ------------------------------------------------------
50
3.5
Landfilling Practice at Al-Akaider Landfill -------------------------------------------------
51
3.6
Impacts and Problems of Al-Akaider Landfill Site -----------------------------------------
54
3.7
Waste Composition and Quantities -----------------------------------------------------------
56
IV
CHAPTER FOUR " RISK ASSESSMENT OF IWW PONDS AND AL-AKAIDER LANDFILL LEACHATE"
58
4.1
Introduction --------------------------------------------------------------------------------------
58
4.2
Green Ampt Model -----------------------------------------------------------------------------
59
4.3
4.4
4.2.1
Introduction ----------------------------------------------------------------------
59
4.2.2
Green-Ampt Model Solution --------------------------------------------------
60
Contaminant Transport under IWW Ponds --------------------------------------------------
63
4.3.1
Theoretical Background --------------------------------------------------------
63
4.3.2
Analysis of IWW arriving at Al-Akaider Landfill --------------------------
64
4.3.3
Contaminant Transport and Breakthrough Curves -------------------------
65
HELP Model -------------------------------------------------------------------------------------
70
4.4.1
Model Description --------------------------------------------------------------
70
4.4.2
Concepts behind the HELP Model -------------------------------------------
71
4.4.3
Input Data ------------------------------------------------------------------------
72
4.4.4
Simulation and Results ---------------------------------------------------------
74
4.4.5
Discussion -----------------------------------------------------------------------
78
4.4.6
Sensitivity Analysis -------------------------------------------------------------
79
4.5
Composition of Leachate Discharged at Al-Akaider Landfill Site -----------------------
81
4.6
SESOIL Model ----------------------------------------------------------------------------------
83
4.7
4.6.1
Model Description -------------------------------------------------------------
83
4.6.2
Concept behind SESOIL -------------------------------------------------------
83
4.6.3
Input Data ------------------------------------------------------------------------
86
4.6.4
Simulation and Results ---------------------------------------------------------
86
4.6.5
Discussion -----------------------------------------------------------------------
90
Risk Assessment and Management of IWW and Leachate -------------------------------
92
CHAPTER FIVE "RISK ASSESSMENT OF AL-AKAIDER LANDFILL GASEOUS EMISSIONS"
94
5.1
Introduction --------------------------------------------------------------------------------------
94
5.2
Gas-Sim Model --------------------------------------------------------------------------------
94
5.3
5.2.1
Concept behind Gas-Sim -------------------------------------------------------
95
5.2.2
Data Required -------------------------------------------------------------------
96
5.2.3
Al-Akaider Landfill Gas Generation -----------------------------------------
97
Land-Gem Model -------------------------------------------------------------------------------
98
5.3.1
Data Required -------------------------------------------------------------------
100
5.3.2
Al-Akaider Landfill Gas Generation -----------------------------------------
100
5.4
Verification of the Models' Output -----------------------------------------------------------
102
5.5
Health Risk Analysis ---------------------------------------------------------------------------
105
5.5.1
Benzene --------------------------------------------------------------------------
105
5.5.2
Hydrogen Sulfide ---------------------------------------------------------------
112
V
5.5.3 5.6
5.7
5.8
Discussion ------------------------------------------------------------------------
116
Environmental Risk Analysis ------------------------------------------------------------------
117
5.6.1
Vegetation Stress ----------------------------------------------------------------
117
5.6.2
Global Impact -------------------------------------------------------------------
118
5.6.2.1
Global Warming Potential ---------------------------------------------
119
5.6.2.2
Ozone Depletion Potential -------------------------------------------
119
Public Health Assessment ----------------------------------------------------------------------
120
5.7.1
Employees, Workers and Recyclers ------------------------------------------
120
5.7.2
Residents of Al-Akaider Village ----------------------------------------------
122
Risk Management -------------------------------------------------------------------------------
124
5.8.1
Workers Risk Management ----------------------------------------------------
125
5.8.2
Residents Risk Management --------------------------------------------------
125
CHAPTER SIX "CONCLUSION AND RECOMMENDATIONS"
127
6.1
Conclusions --------------------------------------------------------------------------------------
127
6.2
Recommendations -------------------------------------------------------------------------------
128
References -------------------------------------------------------------------------------------------------
130
Arabic Abstract --------------------------------------------------------------------------------------------
135
VI
LIST OF FIGURES Page
No.
Description
1.1
Situation Map of the Hashemite Kingdom of Jordan -----------------------------------
1
1.2
Composition of MSW in Jordan -----------------------------------------------------------
4
1.3
Landfilling Practice in Jordanian Landfills, 2005 ---------------------------------------
6
1.4
Landfill Cell with a Steep Slope and 15 m Height --------------------------------------
7
2.1
Schematic Cross Section in a Sanitary Landfill ------------------------------------------
2.2
Gas Generated in a Typical Sanitary Landfill --------------------------------------------
2.3
Exposure Pathways to Landfill Gas -------------------------------------------------------
3.1
Location of Al-Akaider Landfill -----------------------------------------------------------
42
3.2
Al-Akaider Landfill Layout ----------------------------------------------------------------
43
3.3
Geologic Cross Section of the Study Area -----------------------------------------------
44
3.4
Total Annual Rainfall in the Study Area -------------------------------------------------
44
3.5
Frequency Function for Normal Distribution Fitted to Annual Precipitation -------
45
3.6
Average Annual Maximum Temperature in the Study Area ---------------------------
45
3.7
Average Annual Minimum Temperature in the Study Area ---------------------------
46
3.8
Average Annual Solar Radiation in the Study Area ------------------------------------
48
3.9
Wind Rose of the Study Area (1992 – 2002) --------------------------------------------
49
3.10
Average Monthly Climatic Data -----------------------------------------------------------
50
3.11
In Place Combustion of Solid Waste, 1987 ----------------------------------------------
52
3.12
Municipal Solid Waste Compaction at Al-Akaider Landfill ---------------------------
52
3.13
Liquid Waste Disposal at Al-Akaider Landfill ------------------------------------------
53
3.14
Solid Waste Separation at Al-Akaider Landfill ------------------------------------------
54
3.15
Dry Trees due to the Presence of Industrial Wastewater -------------------------------
55
3.16
Composition of Solid Waste Disposed at Al-Akaider Landfill ------------------------
56
4.1
Procedure of IWW Risk Assessment -----------------------------------------------------
59
4.2
st
Breakthrough Curves of Nitrate at the 1 Layer at Different Moisture Contents ---
67
4.3
nd
Breakthrough Curves of Nitrate at the 2 Layer at Different Moisture Contents --
67
4.4
Breakthrough Curves of Nitrate at the 3rd Layer at Different Moisture Contents ---
68
4.5
Procedures of Al-Akaider Landfill Leachate Risk Assessment -----------------------
70
4.6
Annual Leachate Volume Generated at Al-Akaider Landfill --------------------------
75
4.7
Effect of Changing the M.L.A.I. on Leachate Quantity --------------------------------
80
4.8
Effect of Changing the E.Z.D. on Leachate Quantity -----------------------------------
81
4.9
Calibration of a Conservative Material Depth versus Time in Months ---------------
87
4.10
Calibration of a Conservative Material Depth versus Time in Years -----------------
88
4.11
-
89
-
Nitrate (NO3 ) Depth versus Time in Years ----------------------------------------------
4.12
Nitrate (NO3 ) Depth versus Time in Years ----------------------------------------------
89
4.13
Average Annual Dissolved Concentration vs. Time at 306 m Depth -----------------
90
VII
5.1
Schematic Diagram Presenting the Relationship between Models -------------------
95
5.2
Gas-Sim Methane Generation Results (1981 – 2055) ----------------------------------
98
5.3
Land-Gem Methane Generation Result (1981 to 2055) --------------------------------
101
5.4
Comparison of the Methane generated using Two Models ----------------------------
102
5.5
Methane Generated at Al-Akaider & Ruseifeh (Gas-Sim) -----------------------------
104
5.6
Benzene Generated as a Function of Time -----------------------------------------------
106
5.7
Exposure Results of Benzene with Plant Uptake ----------------------------------------
107
5.8
Exposure Pathways of Benzene with Plant Uptake -------------------------------------
108
5.9
Exposure Results of Benzene without Plant Uptake ------------------------------------
109
5.10
Exposure Pathways of Benzene without Plant Uptake ---------------------------------
109
5.11
Wind Rose of Benzene Concentration, 2006 --------------------------------------------
111
5.12
Benzene Concentration at the South West of the Landfill, 2006 ----------------------
112
5.13
Hydrogen Sulfide Emitted from Al-Akaider Landfill ----------------------------------
114
5.14
Vegetation Stress due to CH4 and CO2 ---------------------------------------------------
118
5.15
Workers are at Accident Risk other than Inhalation and Dust -------------------------
121
VIII
LIST OF TABLES No.
Description
Page
1.1
Comparison of MSW Generation Rates --------------------------------------------------
3
1.2
Properties of the Jordanian Landfills ------------------------------------------------------
5
2.1
Pollutants Concentrations in Leachate from a Typical DSW --------------------------
2.2
Typical Landfill Gas Composition --------------------------------------------------------
3.1
Hydraulic Conductivity based on Soil Description -------------------------------------
47
3.2
Seasonally Relative Humidity for the Study Area --------------------------------------
48
3.3
Average Wind Speed and Prevailing Wind Direction ----------------------------------
51
3.4
Estimated Annual Quantity of SW Disposed at Al-Akaider Landfill ----------------
57
4.1
Green-Ampt Infiltration Parameters at Al-Akaider Landfill ---------------------------
61
4.2
Infiltration Rate of the Soil Layers at Different Moisture Contents ------------------
61
4.3
Arrival Time of the Soil Layers at Different Moisture Contents ----------------------
62
4.4
Analysis of Wastewater Arriving at Al-Akaider Landfill ------------------------------
65
4.5
Analysis Results of Drinking Water Samples --------------------------------------------
69
4.6
Input Data Required by HELP Model ----------------------------------------------------
72
4.7
HELP Model Input Parameters ------------------------------------------------------------
73
4.8
Properties of Solid Waste Disposed at Al-Akaider -------------------------------------
73
4.9
Properties of Soil at Al-Akaider Landfill Site -------------------------------------------
73
4.10
Available Leachate Head and Leakage through the Barrier Soil Layer --------------
74
4.11
Water Budget Components at Al-Akaider Landfill (1981 – 2002) -------------------
76
4.12
Average Monthly Values of Water Budget Components ------------------------------
77
4.13
Average Annual Totals for Years 1981 through 2002 ----------------------------------
77
4.14
Peak Daily Values for Years 1981 through 2002 ----------------------------------------
77
4.15
Characteristics of Leachate Sample from Al-Akaider Landfill ------------------------
82
4.16
Input Data of SE-SOIL Model -------------------------------------------------------------
86
5.1
Data Required by Gas-Sim Model --------------------------------------------------------
97
5.2
Data Required by Land-Gem Model ------------------------------------------------------
100
5.3
Solid Waste Composition for Different Landfills ---------------------------------------
103
5.4
Site Data for Al-Akaider and Ruseifeh Landfills ----------------------------------------
103
5.5
Benzene Concentration and Risk at Different Pasquill Categories -------------------
112
5.6
H2S Concentration and Risk at Different Pasquill Categories -------------------------
116
5.7
GWP Species Emitted from Al-Akaider Landfill, 2005 and 2006 --------------------
119
5.8
ODP Species Emitted from Al-Akaider Landfill, 2005 and 2006 ---------------------
120
IX
LIST OF NOMENCLATURE SYMBOL
DESCRIPTION
AT
Averaging Time (days)
BOD
Biochemical Oxygen Demand (mg/L)
BW
Body Weight (kg)
c
Pollutant Concentration in Soil Water (µg/ml)
C
Mass of Carbon Available to Degrade (Mg)
C1
Mass of Waste Deposited (Mg or tones)
Co
Mass of Degradable Carbon at Time t = 0 (tones)
Co,1
Mass of Degradable Carbon at Time t = 0 in Each Fraction (1,2,3,Rapidly, Moderalty & Slowly) (Mg)
Csa
Pollutant Concentration in Soil Air (µg/ml)
Ct
Mass of Degradable Carbon Degraded up to Time t (tones)
Cx
Mass of Carbon Degraded in Year t (Mg)
CEA
Central Environmental Authority
CMR
Colombo Metropolitan Region
COD
Chemical Oxygen Demand (mg/L)
CW
Contaminant Concentration (mg/L)
Dx
Dispersion Coefficient in X-Direction (m2/day)
DSW
Domestic Solid Waste
EC
Electrical Conductivity
ED
Exposure Duration (years)
EF
Exposure Frequency (days/year)
ERA
Environmental Risk Assessment
ET
Evapotranspiration (mm)
EZD
Evaporative Zone Depth (cm)
f
Soil Porosity (ml/ml)
fa
(f-θ) = Filled Air Porosity (ml/ml)
f(t)
Infiltration Rate (m/day)
F(t)
Cumulative Infiltration (m)
GWP
Global Warming Potential
H
Henry's Law Constant (m3.atm/mol)
ho
Initial Depth of Water in the Pond (m)
HELP
Hydrologic Evaluation of Landfill Performance
HI
Hazard Index
I
Chronic Daily Intake (mg/kg of the body/day)
It
Amount of Pollutant Entering the Soil Column during Time Step (µg/cm2)
IR
Ingestion Rate (L/day)
X
ISW
Industrial Solid Waste
IWW
Industrial Waste Water
J
Joules
JD
Jordanian Dinar
JUST
Jordan University of Science and Technology
k
Decay Rate (yr-1)
k
Methane Generation Rate (year-1)
ki
Degradation Rate Constant for Each Fraction of Degradable Carbon (yr-1)
K
Hydraulic Conductivity (m/day)
Kd
Pollutant Portioning Coefficient (µg/g)/(µg/ml)
Kd
Soil Distribution Coefficient (ml/g)
L
Methane Generation Capacity (m3/Mg)
L1
Landfill Gas Generation Capacity (g/Mg)
LFG
Landfill Gases
LL
Lower Limit
LULU
Locally Undesirable Land Use
M
Relative Molecular Mass of Carbon (mol/g)
Mt
Amount of Pollutant Migrating Out of the Soil Column during the Time Step (µg/cm2)
MLAI
Maximum Leaf Area Index
MSW
Municipal Solid Waste
MSWLF
Municipal Solid Waste Landfills
n
Freundlich Exponent
NTU
Nephelometric Turbidity Unit
P
Precipitation (mm)
PPM
Part Per Million
Ot-1
Amount of Pollutant Originally in the Soil Column at Time t-1 (µg/cm2)
ODP
Ozone Depletion Potential
R
Retardation Factor
R
Universal Gas Constant [8.2 × 10-5 (m3 × atm)/(mol × ºK)]
R2
Coefficient of Determination
Rt
Amount of Pollutant Remaining in the Soil Column at Time t (µg/cm2)
RfD
Reference Dose (mg/kg.day)
RO
Runoff (mm)
s
Pollutant Adsorbed Concentration (µg/g)
SCS
Soil Conservation Service
SD
Standard Deviation
Se
Effective Saturation
SF
Slope Factor (kg.day/mg)
SW
Solid Waste
SWRRB
Simulator for Water Resources in Rural Basins
XI
t
Time (years)
t
Time between waste emplacement and LFG generation (yr)
T
Soil Temperature (ºC)
Tt
Amount of Pollutant Transferred within the Soil Column at Time Step (µg/cm2)
UL
Upper Limit
US EPA
United States Environmental Protection Agency
Vm
Molar Volume at STP (2.241 × 10-2 m3 mol-1)
vx
Flow Velocity in X-Direction (m/day)
x
Distance (m)
ψ
Soil Suction Head (m)
ρb
Soil Bulk Density (g/cm3)
Ө
Soil Moisture Content (%)
∆Ө
Porosity – Moisture Content
∆S
Change in Water Storage (mm)
XII
ENVIRONMENTAL AND HEALTH RISK ASSESSMENT OF AL-AKAIDER LANDFILL
Eng. Luay I. Qrenawi Supervised By: Chairman: Dr. Hani Abu Qdais Co-Advisor: Dr. Fayez Abdulla
ABSTRACT Al-Akaider landfill is one of the hot environmental spots in Northern Jordan. It is located within the boundaries of Al-Mafraq Governorate at a distance of 27 km east of Irbid City and about 1 km from the Jordanian / Syrian border. Solid waste deposition in the landfill started in 1981 and it is intended to close the landfill in 2020. Al-Akaider landfill is managed by the Common Services Council of Irbid City. The landfill receives MSW with a quantity of 700 tones/day produced from the inhabitants about 62 villages and cities Northern Jordan. Industrial wastewater from slaughterhouses, dairy industry, dyeing industry and chicken sludge are being disposed at special evaporation ponds at the site. The objectives of the present study are to review the situation of the current landfilling practices at Al-Akaider landfill, identify and assess the environmental and health risks associated with Al-Akaider landfill and to recommend management options to minimize such risks. The work throughout this study is divided into tow major categories; risk assessment of industrial wastewater ponds and leachate at Al-Akaider landfill site and risk assessment of gaseous emissions released from the landfill and their impacts on the neighboring communities and the surrounding environment. For the industrial wastewater ponds at Al-Akaider landfill site; the arrival time of nitrate as a conservative material to the groundwater table was estimated by solving the Green-Ampt model at different moisture contents. The estimated arrival time raged from 18.72 to 22.21 years. Experimental program was also conducted to analyze IWW samples arriving at Al-Akaider landfill. The contaminant transport model was utilized to construct the breakthrough curves of nitrate through each soil layer at different moisture contents and the arrival time ranged from 18.5 to 22.2 years indicating that the contamination of groundwater has already taken place. For leachate discharged from the landfill; HELP 3 model was utilized to quantify the amount of leachate. The model indicated that the average volume of leachate discharged from Al-Akaider landfill in the period from 1981 to 2002 was about 5500 m3/year. To study the transport of nitrate from landfill leachate to the groundwater at the site the SE-SOIL model was utilized. The output of HELP 3 and the results of leachate sample analysis were fed into the SE-SOIL model. The arrival time of nitrate from leachate to the groundwater at the site was about 23 years indicating that the contamination of groundwater by leachate has already occurred.
XIII
To verify these results; groundwater samples from two wells at the area (one from upstream and the other from downstream) were obtained and analyzed. The results of analysis supported the notion that groundwater contamination at Al-Akaider landfill region has already occurred. The risk associated with the contamination of groundwater was acceptable for adults while it was unacceptable for children and it value is expected to increase in the future. Gaseous emissions from the landfill were quantified by using Gas-Sim model while the Land-Gem model was utilized to verify the results obtained by Gas-Sim. Risk assessment of two gases (benzene as a carcinogen gas and hydrogen sulfide as a noncarcinogen gas) was conducted and then surrogate chemicals accounting for 99 % of the risk were selected. The results were: both the carcinogenic and non-carcinogenic risks to the residents of Al-Akaider village (1580 m south west the landfill) were minimal while they were not acceptable for workers. The lateral migration model indicated that vegetation will be affected due to the depletion of oxygen and presence of carbon dioxide and methane in concentrations above 7.5 % (by volume) in the root zone at a distance of 157 m around the landfill. The global warming potential model revealed that the landfill will emit 194,247 tones CO2 equivalent while the ozone depletion potential indicated that the landfill will emit 1.78 tones CFCl3 equivalent in the year 2006. The study also outlined that Al-Akaider village residents are not adversely affected by Al-Akaider landfill and their complains are due the lack of proper excreta disposal system in some houses, the lack of proper refuse and solid waste disposal system, improper control of houseflies and lack of personal hygiene due to lack of sanitary facilities in some houses. The study recommended that sanitary landfill sites should be designed as an engineering facility to minimize the adverse effects associated with solid waste disposal, the transport of contaminants other than nitrate should be investigated, monitoring wells should be installed to regularly analyze the quality of groundwater and to suggest the possible uses of such waters, methane recovery should be considered as part of any integrated solid waste management plan, Al-Akaider village housing conditions should receive high priority from the government and the responsible authorities. Waste reduction, reuse and recycling should be encouraged; segregation of recyclable materials should be performed before the waste being disposed at the landfill to minimize the exposure of recyclers to landfill emissions. Community participation should be encouraged through education making and awareness campaigns as much as possible.
XIV
CHAPTER ONE INTRODUCTION
1.1 Statement of the Problem Jordan is located in the Middle East with geographic coordinates of 31 00 N, 36 00 E. It has a total area of 89,213 km2; land portion is about 88,884 km2 while water portion is 329 km2. The population of Jordan is about 5.759 millions with a growth rate of about 2.8 % (1, 2).
Figure 1.1: Situation Map of the Hashemite Kingdom of Jordan (2)
The Middle East region is a meeting point of many escalating environmental threats especially in the solid waste sector (3). This is particularly the case in Jordan which is a country with limited natural resources and a high population growth rate due to the three waves of immigration resulting from the Gulf Wars and the occupation of Iraq. The combination of population increase together with the other economic and technical constrains have challenged planners and decision makers to develop strategies to solve
1
many of difficult problems in Jordan. This also renders Jordan to be vulnerable to a broad spectrum of environmental challenges; moreover it suffers from limited natural fresh water resources, solid waste problems, deforestation, overgrazing, soil erosion and desertification (4, 5)
.
Progress in formulating environmental policies in Jordan is slow so far, but the government acknowledges the importance of reconciling environmental concerns and development needs (4). Municipal solid waste management is a growing concern in Jordan, but it has been complicated by the sharp increases in the volumes of the generated solid wastes as well as the qualitative changes in the composition of these wastes due to the significant changes in the living standards and conditions (5).
Financial constrains, shortage of adequate and proper equipment and the limited availability of trained and skilled manpower have contributed much to the poor solid waste management program in Jordan. Low level of awareness and education regarding the health and environmental impacts of improper management of solid waste has also aggravated the problem (5).
Municipal solid waste in Jordan is generated from the following sources: 1. Residential areas (houses, parks) 2. Commercial areas (shops, offices, restaurants, hotels and markets) 3. Wastewater treatment facilities (residuals) 4. Industrial activities (small manufacturing, trades) 5. Agricultural sectors (animal waste, farm waste and olive mills) 6. Institutional areas (universities, schools, hospitals, prisons)
2
In Jordan; solid waste is stored in containers and then transported to a landfill. Works crews clean the streets and collect residential wastes which are transported by dump trucks and waste compactors for final disposal. The collection system is adequate in urban centers, but services tend to be poor or nonexistent in rural areas and small villages (4, 5). 1.2 Characteristics of Solid Waste in Jordan 1.2.1
Solid Waste Generation Rate The average generation rate of solid waste in Jordan ranges from 0.72 to about 0.91
kg/cap/day. It is observed that the Jordan per capita production rate is similar to rates of other economically developing countries but significantly less than that of more developed countries, see Table 1.1. The total estimated daily generation of municipal solid waste in Jordan is about 3700 ton/day; disposed at 24 landfills. The northern region contributes about 800 ton/day while the middle region totals about 2500 ton/day and the southern region contributes about 400 ton/day (3, 5, 6). Table 1.1: Comparison of MSW Generation Rates (3, 5, 7) Country
Per capita generation rate (kg/cap/day)
Jordan
0.82*
Palestine
0.85
Kuwait
1.37
Seoul, Korea
2.0
Vienna, Austria
1.18
Mexico city, Mexico
0.68
Paris, France
1.43
Australia
1.87
USA
2.0
* Average Value
3
1.2.2
Solid Waste Composition Many studies have been performed on the composition of municipal solid waste in
Jordan and almost all studies agree that; municipal solid waste in Jordan is characterized by a high organic content. Food waste constitutes more than 60 % of the total waste at source; see Figure 1.2, the organic matter is higher at the majority of Jordanian disposal sites. The bulk density of municipal solid waste is about 0.37 ton/m3 at source but it may be found to be 0.6 ton/m3 after compaction in collection vehicles
(5, 8)
. The calculated
gravimetric moisture content of municipal solid waste arriving at Al-Akaider landfill is 48.64 %.
Glass; 7
Metals; 5
Others; 2
Fiber; 1 Paper; 16
Food Waste; 56
Plastic; 13
Figure 1.2: Composition of MSW in Jordan (9)
1.2.3
Final Disposal Sites of Solid Waste The disposal sites for municipal solid waste (landfills) in Jordan are distributed as
follows: seven in the northern region, eight in the middle and ten in the southern region. They are spread all over the country and most of them are close to the heavily populated areas. The largest is the new Ghabawi landfill located in the middle region of the country, the second largest is the Russeifeh closed landfill located also in the middle highly populated region of Jordan while the third largest is Al-Akaider landfill located in the northern part of the country. The Jordanian landfills and their characteristics are listed in Table 1.2. 4
Table 1.2 Characteristics of the Jordanian Landfills (5, 10) Region
Landfill
Location
Area (1000 m2)
Waste Received
North
Al-Akaider
Mafraq
806
MSW, ISW & IWW
North
Om Qutain
Mafraq
400
MSW
North
Mafraq
Mafraq
180
MSW, ISW
North
North Shuneh
North Shuneh
78
MSW and medical
North
Kufrinja
Ajloon
71
MSW
North
Taybeh
Irbid
60
MSW
North
Saro
Bani Kinana
55
MSW
Middle
Ghabawi
Ghabawi
2000
MSW
Middle
Russeifeh
Russeifeh
1200
MSW, ISW and medical
Middle
Humra
Sult
275
MSW and Medical
Middle
Dier Allah
Middle Ghor
200
MSW
Middle
Madaba
Madaba
80
Middle
Dhuliel
Dhuliel
70
MSW
Middle
Azraq
Azraq
48
MSW
Middle
Thiban
Madaba
30
MSW
South
Karak
Karak
600
MSW and septage
South
Ma’an
Ma’an
502
Septage and spent oils
South
Tafila
Tafila
450
Medical and septage
South
Eil
Ma’an
280
MSW
South
Quaireh
Aqaba
270
MSW
South
South Ghor
South Ghor
153
MSW
South
Huseinyeh
Huseinyeh
100
MSW
South
Aqaba
Aqaba
60
MSW, ISW and medical
South
Shobak
Shobak
26
MSW
South
South Shuneh
South Shuneh
10
MSW
MSW, ISW, medical & Queen Alia Airport Wastes
Site selection of these landfills has not been based on feasibility studies that take environmental or health issues in consideration. For example; the Russeifeh landfill is overlying an important groundwater aquifer; Amman Wadi As-Sir (5).
5
1.3 Landfilling Practices in Jordan The methods of landfilling currently practiced in Jordan do not rise to the engineering definition of landfilling as followed in the developed countries. In well managed sites, the major landfilling activities include waste placement, spreading, covering with daily cover of indigenous soils and then compacting the different lifts to an approximate height of 9.5 to 15 m (5), Figures 1.3 and 1.4.
Figure 1.3: Landfilling Practice at Al-Akaider Landfill, 2005
Leachate collection and removal systems are not available at all in any landfill in Jordan except at the new Ghabawi landfill. Also, gas collection systems were not used except for Russeifeh landfill; where a pilot gas recovery and conversion project was recently built on the landfill site. This site has been closed and all solid waste is to be transported to a new and better managed landfill called Ghabawi (5).
6
Figure 1.4: Landfill Cell with a Steep Slope and 15 m Height
Observations at Jordanian Landfills raise the following concerns: 1. Some Jordanian landfills receive untreated industrial and medical wastes. Since these wastes are potentially hazardous, this practice may have adverse impacts on health and the environment. The fact that no gas collection, leachate collection, or liner systems exist exacerbates the danger of this practice 2. Unsanitary landfilling is still practiced at many landfills which is unacceptable and poses an environmental hazard. Unsanitary landfilling attracts rodents and flies and therefore forcing the local municipalities to spray pesticides in alarming quantities to control these vectors. Unfortunately, new strains of insects that are immune to pesticides have resulted which pose a serious challenge to the human health (5) 1.4 Objectives of the Study The main objective of this research is directed towards the assessment of environmental and health risks of Al-Akaider landfill. The specific ones are:
7
1. Review the situation of the current landfilling practices at Al-Akaider landfill 2. Identify and assess the environmental and health risks associated with Al-Akaider landfill 3. Recommend management options to minimize the risks associated with the landfilling practices at Al-Akaider landfill 1.5 Overall Methodology The methodology followed in this research was as follows: 1. Data collection and preparation; the collected data included solid waste quantities, sources, characteristics, rate of their generation, solid waste composition, final disposal options, description of Al-Akaider landfill (area, location, topography, groundwater depth, quantity and type of waste deposited). 2. Analysis of industrial wastewater disposed at Al-Akaider landfill 3. Studying the transport of nitrate from the industrial wastewater at Al-Akaider landfill to the subsurface layers. 4. Quantification of leachate discharged from Al-Akaider landfill and analysis of leachate sample. 5. Studying the transport of nitrate from leachate to the groundwater 6. Verification of the results by analyzing groundwater samples and performing the risk assessment and management. 7. Quantification of landfill gaseous emissions, verification of results, risk assessment and risk management.
1.6 Thesis Organization This thesis has been organized in six chapters: Chapter One is a general introduction considering solid waste status and landfills in Jordan. Chapter Two presents a
8
brief background on landfills and problems and impacts associated with landfilling processes; it also presents the emissions of landfills (leachate and gases), finally; a quick review of the risk assessment process and summary of some previous relevant studies are presented. In Chapter Three, description of the study area (Al-Akaider landfill) in terms of location, topography, climate, hydrology and geology is covered furthermore past and current landfilling practices are reviewed. Chapter Four is directed towards risk assessment of industrial wastewater ponds at the site and the landfill leachate, while Chapter Five is devoted to assess the environmental and health risks associated with the landfill gaseous emissions on workers and residents in the proximity of the landfill. Thesis conclusions and recommendations are presented in Chapter Six.
9
CHAPTER TWO LITERATURE REVIEW
2.1 Introduction Landfill, a waste management option, is the term used to describe the physical facilities and areas of land or excavations that are used for permanent disposal of solid waste, i.e., waste is dumped with the objective of leaving it there indefinitely. Since the turn of the last century, the use of landfills has been the most economically and environmentally acceptable method for solid wastes disposal through the world (11, 12, 13, 14). Depending on location; up to 95 % of solid waste generated world wide is currently disposed of in landfills. Therefore, landfills will continue to be the most attractive disposal route for solid waste and will remain as an integral part of most solid waste management plans (15). Landfilling is the term used to describe the process by which solid wastes are placed in the landfill
(12)
. Landfilling has been used for many years as the most common
means for solid waste disposal generated by different communities
(16)
. In the past, the
term sanitary landfill was used to denote a landfill in which the waste was placed and covered at the end of each day's operation. Today, sanitary landfill refers to an engineered facility for the disposal of municipal solid waste (MSW) designed and operated to minimize public health and environmental impacts (12). Figure 2.1 shows a schematic cross section in a sanitary landfill.
10
Final Landfill Surface Gas Vents
Previous layer for Liner Protection and Leachate Collection Runoff Control
Soil Layer to Establish Vegetation Sealing Layer Intermediate Layer
Slope Stabilization
Leachate to Treatment Monitoring Well
Monitoring Well Secure Landfill
Run-on Control
Leachate Collection
Impervious Liner Leachate Detection System
Secondary Liner
Water Table
Figure 2.1: Schematic Cross Section in a Sanitary Landfill (17) 2.2 Landfill Siting Considerations While alternative waste disposal methods – incineration along with the advent of recycling, composting, and pollution prevention – are scaling back the numbers of active landfills, the engineering construction and operation of landfills are now more complex than ever. Driven by public pressure and subsequent regulatory requirements, landfill design and operation now have to conform to strict standards (13). One of the most difficult tasks faced by public agencies and private management firms in the implementation of an integrated solid waste management program is the siting of a new landfill. Siting a sanitary landfill requires substantial evaluation process in order to identify the best available disposal location. The location must comply with the requirements of governmental regulations and at the same time minimizes economic, environmental, health and social impacts. To achieve a successful siting process, several significant political and environmental obstacles have to be overcome. Factors that must be considered in evaluating potential sites for the long term disposal of solid waste include: 1. Distance from waste generation source and waste type 2. Depth to groundwater and groundwater quality from observation wells 11
3. Distance from residential, religious and archaeological sites 4. Site access and capacity 5. Soil characteristics, clay content, topography and land slope 6. Climatic conditions 7. Existing land use pattern and land cost 8. Local environmental conditions 9. Distance from airports 10. Ease of access in any kind of weather to all vehicles expected to use it 11. Seismic activity (12, 14, 16) Final selection of a disposal site is usually based on the results of detailed site survey, engineering design, cost studies, the conducting of one or more environmental impact assessments, the outcome of public hearings and a sober analysis of presently operating landfills. The environmental impacts of new landfills must be as low as possible for as long period as possible. This means that; environmental impact assessment and safety analyses are therefore necessary in each and every case. Landfills are often viewed as LULUs (Locally Undesirable Land Uses). With this in mind; the public's viewpoint must be incorporated into the landfill development process. Local or international regulations may specify special procedures for interacting with the public when siting a new landfill. Often an extensive public information and negotiation process must be conducted concurrently with the technical development activities to site a new landfill successfully. The public's challenge to landfill during the siting process is understandable, but economic impact studies of landfills generally do not show widespread reduction of property values (12, 14, 16).
12
2.3 Location Restrictions of Landfills There are six restricted areas where landfill location is restricted, they are: sites located near airports, floodplains, unstable areas, wetlands, seismic impact zones and fault areas. These areas are unsuitable for operating municipal solid waste landfills (MSWLFs), unless the MSWLF can meet the specific criteria stated under the rule for each location (13).
2.4 Environmental Impacts of Landfills Landfills were initiated as a result of a need to protect the environment and society from adverse impacts of alternative methods of refuse disposal. Although landfills eliminated some impacts of old practices new ones arose; primarily due to gas and leachate formation. Concerns also include fires, explosions, noise, dust, aesthetics, vegetation damage, unpleasant odors, vectors, birds, landfill settlement, groundwater contamination, surface water pollution, floods, air pollution and global warming. Of these, the production of gas and leachate – which can persist over 20 years and more – are the most troublesome. While easy to prevent during landfilling by following one of several approved techniques, subsequent prevention of these conditions after poor landfilling methods is extremely difficult if not impossible (15, 18). Each of these environmental factors is discussed below.
2.5 Leachate Leachate is a dark brown / black by-product liquid with a strong odor formed and begins to be discharged at the bottom of the landfill if fill soil and solid waste receive enough water to reach their respective field capacities. In general, leachate is a result of the percolation of precipitation, uncontrolled runoff and irrigation water into the waste matrix in the landfill. Leachate will also include water initially contained in the waste (12, 18).
13
Leachate contains a variety of chemical constituents derived from the solubilization of materials deposited in the landfill and from the products of chemical and biochemical reactions occurring within the landfill (12). Water inflow to a landfill can be reduced by the following measures: •
Locate the landfill so as to avoid direct groundwater or surface water contact
•
Use proper surface cover grading to increase rain water runoff
•
Plant
the
landfill
cover
to
avoid
erosion
by enhancing
runoff
and
evapotranspiration •
Use a non-permeable cover material with maximum lateral-flow characteristics
•
Delay leachate generation by placing solid waste and soil cover with low moisture contents and high compaction densities
•
Install drainage facilities to divert off-site surface and subsurface waters.
Although leachate quality is different in each municipal landfill, generally; landfill leachate is highly dependent on the stage of fermentation within the landfill. Other variables affecting it include the age of the waste at the landfill, annual rainfall, ambient temperature, final cover, layer permeability and depth, waste composition, biological activity, compaction of the waste in the landfill, operational procedures and co-disposal of industrial wastes. Many chemicals have been detected in landfill leachate from domestic, commercial, industrial, and co-disposal sites. All groundwater sources are potentially at risk from landfill leachate (13, 18, 20). The biological activity in the landfill significantly changes the chemical environment. The biodegradable organic solids are hydrolyzed, and in many cases the product is an organic acid. The pH becomes acidic, usually less than 5. Also, the oxidation reduction potential is lowered into the range where many metals are soluble. The
14
combination of low pH, high salts concentration and reduced metals create very corrosive environment that is responsible for converting many of the metals in the refuse into ions (20)
. Table 2.1 outlines the range of pollutant concentrations in leachate from a typical
domestic solid waste refuse. Table 2.1: Pollutants Concentrations in Leachate from Domestic Solid Waste (20, 21) Concentration (mg / L)
Ion
Lower Limit
Upper Limit
Phosphate
5
130
Sulfate
25
500
Chloride
100
2,400
Sodium
100
3,800
Calcium
60
7,200
Potassium
28
3,770
Magnesium
17
15,600
Nitrogen
20
500
Phosphorus
0
130
Hardness (as CaCO3)
200
5,250
Alkalinity (as CaCO3)
240
20,500
Biochemical oxygen demand
40
29,200
Chemical oxygen demand
100
51,000
Dissolved solids
584
44,900
Suspended solids
10
700
Nickel
0.01
0.8
Copper
0.1
9
Iron
200
1700
Cadmium
0
17
Zinc
1
135
Lead
0
2
pH (no unit)
4
8.5
In general, leachate concentration – BOD – of initial landfill is higher than at any time, and then gradually reduces with increasing landfill age. The reason for the lower leachate concentration during rainy seasons is due to leachate dilution with rainwater.
15
However, increasing concentrations in an initial period of rainfall is expected due to the fresh wash out effect. Leachate emerged from landfills has a BOD of about 100 times stronger than raw sewage. As a landfill ages, the refractory high molecular weight compounds were found instead of degradable organic matter. It is noted in literature that the ratio BOD/COD decreases sharply within approximately one year and then progressively level off with increasing landfill age. This phenomenon indicates that reactions of biodegradable organics are rapid during the first year and then a steady state is soon reached, i.e. the proportions of biodegradable organics decreases already greatly after about one year. After this period, the micro-biological reactions of BOD degradation are limited. Another reason for decreasing this ratio is probably due to rain water washout. From the above discussion, it is implied that the major processes of leachate treatment are biological processes before about one year of landfill age and biodegradable organics become low after one year. The treatment of leachate usually requires an extra chemical aided precipitation system or pretreatment procedures. To develop more efficient and reliable treatment processes to transform leachate into innocuous materials it is necessary to revise the design and operational parameters based on the landfill age (13, 19).
2.6 Impacts of Landfill Leachate 2.6.1
Groundwater Contamination Leachate generation and impacts to groundwater are of special concern when
investigating existing municipal landfill sites. Small amounts of landfill leachate can pollute large amounts of groundwater; rendering them unusable for domestic and many other purposes
(13, 22)
. Experience gained during the last decades has shown that leachate
poses an important hazard for the environment. Numerous cases of groundwater pollution from unprotected landfills are described in literature (23).
16
Dumps and landfill sites, legal or illegal, are potential sources of groundwater pollution if they are underlined by permeable rock and soil. Rainwater infiltrating from above and dissolving additional soluble chemicals from the waste compounds the problem. A variety of dangerous household chemicals; paint and solvents, pesticides, and many others are likely to be found in municipal solid waste landfills
(18)
. Pollution of
groundwater by leachate poses a great threat because it contains multiple pollutants that may not be easy to remove or treat (22). Gravity causes leachate to move through the landfill and through the underlying soil until it reaches the aquifer. As leachate moves down to the subsurface, they mix with groundwater held in the soil spaces and this mixture moves along the groundwater’s flow path as a plume of contaminated groundwater. The leachate contaminants first enter the unsaturated zone and eventually are transported to the groundwater table in the saturated zone. The most important indictor that reflects the leachate moving through the subsurface groundwater aquifer beneath the landfill is the increase in the concentration of inorganic constituents, which represent a threat to groundwater quality (22).
2.6.2
Surface Water Pollution The pollution of surface waters (lakes and streams) by leachate is not a significant
problem. It is an unusual site design that causes the leachate to exit the landfill above ground. If this happens; the concentrated leachate causes severe pollution of surface water. The high BOD rapidly depletes the dissolved oxygen in the water and causes fish death in a very short time. Additional contamination is related to the various metals that may be present in the leachate. If the leachate does exit the fill above the elevation of the
17
surrounding ground, it can be expected to cause severe water pollution when it enters a surface water reservoir (20). The release of solid wastes to surface waters may also result in acute and chronic human health problems. The primary route to exposure is through drinking water. However, the consumption of fish and other aquatic organisms that accumulate chemicals is also a concern, since human health effects may occur at lower levels of bioaccumulation relative to those that effect indigenous aquatic organisms (18). A major concern associated with the contamination of surface waters is that existing ambient water quality criteria for human toxic and carcinogenic protection are in many cases below detection limits in water. Potentially toxic releases to surface waters from landfill facilities can therefore go undetected. Contaminant releases to surface waters that result in widespread long-term degradation of water quality can also affect agricultural and industrial use (18).
2.7 Reduction of the Impacts of Leachate on Groundwater As leachate poses a great threat to groundwater, it is necessary to develop and design a certain system within the landfill that controls it. The control of leachate can be accomplished in two ways: 1. Prevent the precipitation from entering the refuse by an appropriate cover 2. Collect and treat the leachate produced within the site If the moisture conditions are such that the formation of leachate can be prevented without an expensive cover, this is the preferred technique for control. However, if excessive precipitation exists and leachate production is likely, it is necessary to prepare suitable systems for its collection and treatment. It is still appropriate to design a cover that will reduce the inflow of water (20). A typical system to control leachate includes:
18
•
Leachate collection system
•
Man made top barrier (Top Flexible Membrane Liner)
•
Leak detection system
•
Natural barrier / liner (1)
2.8 Landfill gas Several gases are generated by decomposition process of organic materials in a landfill. The composition, quantity, and generation rates of the gases depend on such factors as refuse quantity, density and composition, placement characteristics, landfill depth, refuse moisture content, temperature and amount of oxygen present
(24)
. Three
processes form landfill gas, they are: bacterial decomposition, volatilization and chemical reactions. These processes are discussed below:
2.8.1
Bacterial Decomposition Most landfill gas is produced by bacterial decomposition, which occurs when
organic waste is broken down by bacteria naturally present in the waste and in the soil used in the landfill cover. Organic wastes include food, garden waste, street sweepings, textiles, wood and paper products. Bacteria decompose landfill waste in four phases. The composition of the gas produced changes with each of the four phases of decomposition. Landfills often accept waste over a 20 to 30 year period, so waste in a landfill may be undergoing several phases of decomposition at once. This means that older waste in one area might be in a different phase of decomposition than more recently buried waste in another area (24).
(1) Detailed description of leachate collection system is found in Reference 14 and 17 19
2.8.1.1 Phase I During the first phase of decomposition, aerobic bacteria consume oxygen while breaking down the long molecular chains of complex carbohydrates, proteins and lipids that comprise organic waste. Considerable heat is generated and the principal gas generated is carbon dioxide (CO2). Nitrogen content is high at the beginning of this phase, but declines as the landfill moves through the four phases. Phase I continues until available oxygen is depleted. Phase I decomposition can last for days or months; depending on how much oxygen is present when the waste is disposed of in the landfill. Oxygen levels will vary according to factors such as how loose or compressed the waste was when it was buried. Figure 2.2 shows typical variations with time in landfill oxygen, carbon dioxide and methane (24).
2.8.1.2 Phase II Phase II decomposition starts after the oxygen in the landfill has been used up. Using an anaerobic process, bacteria convert compounds created by aerobic bacteria into acetic, lactic and formic acids and alcohols such as methanol and ethanol. The landfill becomes highly acidic. As the acids mix with the moisture present in the landfill, they cause certain nutrients to dissolve, making nitrogen and phosphorus available to the increasingly diverse species of bacteria in the landfill. The gaseous byproducts of these processes are carbon dioxide and hydrogen. If the landfill is disturbed or if oxygen is somehow introduced into the landfill, microbial processes will return to Phase I (24).
20
Figure 2.2: Gas Generated in a Typical Sanitary Landfill (24) 2.8.1.3 Phase III Once the landfill’s free oxygen is depleted, organic decomposition becomes anaerobic so that the principal gases generated are methane (CH4) and carbon dioxide (CO2). Some hydrogen sulfide (H2S) generation has been noted in landfills which have substantial quantities of sulfate salts. Volatile organic compounds may also be present in landfill gases; particularly at co-disposal facilities. Phase III decomposition starts when certain kinds of anaerobic bacteria consume the organic acids produced in Phase II and form acetate; an organic acid. This process causes the landfill to become a more neutral environment in which methane producing bacteria begin to establish themselves. Methane and acid producing bacteria have a symbiotic, or mutually beneficial, relationship. Acid producing bacteria create compounds
21
for the methanogenic bacteria to consume. Methanogenic bacteria consume the carbon dioxide and acetate, too much of which would be toxic to the acid producing bacteria (24). 2.8.1.4 Phase IV Phase IV decomposition begins when both the composition and production rates of landfill gas remain relatively constant. Phase IV landfill gas usually contains approximately 45% to 60% methane by volume, 40% to 60% carbon dioxide, and 2% to 9% other gases, such as sulfides. Gas is produced at a stable rate in Phase IV, typically for about 20 years; however, gas will continue to be emitted for 50 or more years after the waste is placed in the landfill. Gas production might last longer, for example; if greater amounts of organics are present in the waste, such as at a landfill receiving higher than average amounts of domestic animal waste
(24)
. Table 2.2 outlines a typical landfill gas
composition. Table 2.2: Typical Landfill Gas Composition (15) Component
2.8.2
Concentration range (%) Lower Limit
Upper Limit
Methane
40
70
Carbon dioxide
30
60
Carbon monoxide
0
3
Oxygen
0
5
Nitrogen
0
3
Hydrogen
0
5
Hydrogen sulfide
0
2
Trace compounds
0
1
Volatilization Landfill gases can be created when certain wastes, particularly organic compounds,
change from a liquid or a solid into a vapor. This process is known as volatilization. Non
22
methane organic compounds in landfill gas may be the result of volatilization of certain chemicals disposed of in the landfill (24). 2.8.3
Chemical Reactions Landfill gas, including non methane organic compounds, can be created by the
reactions of certain chemicals present in waste. For example; if chlorine bleach and ammonia come in contact with each other within the landfill, a harmful gas is produced (24)
.
2.9 Gas Collection System Gas control can be both difficult and expensive. Two common techniques used to control gas movement: 1. Passive collection systems 2. Active collection systems (2) Constructing a gas collection and treatment system should be considered where: 1. Existing or planned homes or buildings may be adversely affected through either explosion or inhalation hazards 2. Final use of the site includes allowing public access 3. The landfill produces excessive odors
2.10
Impacts of Gases Generated in Landfills
2.10.1 Health Impacts Gases generated in landfills normally take the shortest or easiest route to the surface. Occasionally; the presence of fissures in or surrounding the filled land, possibly together with the presence of surface barrier will cause the evolved gases to travel large distances horizontally. In some cases, these gases found their way into basements of
(2) Detailed description of gas collection systems is found in Reference 17, 21, and 25 23
houses and buildings and deaths and injuries have resulted from asphyxiation, poisoning or from detonation of explosions of air methane mixtures. Possible pathways of landfill gas are illustrated in Figure 2.3 (11, 26).
Figure 2.3: Exposure Pathways to Landfill Gas (26) 2.10.2 Global Warming Emissions of methane and carbon dioxide from landfill surfaces contribute significantly to global warming or the greenhouse effect. Methane has received recent attention as a contributor to global warming because on a molecular basis, it has a relative effect 20 to 25 times greater than carbon dioxide, it is more effective at trapping infrared radiation and tends to persist longer in the atmosphere owing to other species (carbon monoxide) with a greater affinity for hydroxyl ions, the oxidizing agent for methane. Recent increases of methane concentrations in the atmosphere have lead to extensive characterization studies of global methane sources and sinks. Atmospheric methane concentrations were reported to increase at an average rate of about 1 to 2% per year. It is estimated that methane contributes about 18% towards total global warming.
24
This contribution represents 500 million tons per year approximately of which 40 to 75 million tons are attributed to emissions from landfills. Due to continuing trends in population increase and urbanization, solid waste landfills are becoming a significant contributor to atmospheric methane, unless recovery control systems are implemented (15).
2.10.3 Fires and Explosions Although landfill gas, rich in methane, provides an energy recovery opportunity, it has often been considered to be a liable because of its flammability and ability to form explosive mixtures with air in concentrations from 5 to 15 % by volume. Methane has the tendency to migrate away from the landfill boundaries by diffusion and advection. Diffusion and advection rates depend primarily on the physical properties and generation rates of the landfill gas, refuse permeability, internal landfill temperature, moisture content, surrounding soil formation and changes in barometric pressure. The migrating gas finds its way into buildings and underground facilities erected on or near to a landfill site where it forms gas pockets and creates potential explosive hazards. Depending on the soil characteristics, the gas may travel long distances away from the landfill prior to being discovered. Numerous incidents of fires and explosions due to lateral gas migration away from landfills have been reported in the literature. Fire and explosion hazards are not limited to incidents away from the landfill. Onsite fires are common and many occur in the subsurface due to air entrainment into the landfill and the formation of a mixture of methane and oxygen that can sustain a fire. Air entrainment occurs primarily as a result of excessive withdrawal rates from gas recovery or migration control systems. In addition, surface cracks and temperature gradients can create a chimney effect and entrain air into the landfill (15, 18).
25
2.10.4 Unpleasant Odors Odors are mainly the result of the presence of small concentrations of odorous constituents (esters, hydrogen sulfide, organosulphurs, alkyl-benzenes, limonene and other hydrocarbons) in landfill gas emitted into the atmosphere. The odorous nature of landfill gas may vary widely from relatively sweet to bitter and acrid depending on the concentration of the odorous constituents within the gas. These concentrations will vary with waste composition and age, decomposition stage and the rate of gas generation and the nature of microbial populations within the waste. Although many odorous trace compounds may be toxic, they have historically been perceived more as an environmental nuisance than as a direct health hazard. The extent to which odors spread away from the landfill boundaries depends primarily on weather conditions; wind, temperature, pressure and humidity (15, 18).
2.10.5 Vegetation Damage At closure, many landfill sites are converted to parks, golf courses, agricultural fields and – in some cases – commercial developments. Vegetation damage at or nearby to such sites is well documented in the literature
(15)
. The damage occurs primarily due to
oxygen deficiency in the root zone resulting from a direct displacement of oxygen by landfill gas. In the absence of a gas control measure, landfill gas can migrate upward due to concentration and pressure gradients and escape into the atmosphere by venting through the landfill cover. During this process; oxygen is displaced and plant roots are exposed to high concentrations of methane and carbon dioxide; the two major constituents of landfill gas. The lack of oxygen causes the death of plants of asphyxia (18).
26
Although direct exposure to methane may not affect the growth of plants, methane oxidation near the surface by methane consuming bacteria is another factor that contributes to oxygen deficiency. Oxygen is consumed according to:
CH 4 + 2O2 → CO2 + 2 H 2 O + Heat
..............................(2.1)
Heat release during methane oxidation increases the soil temperature creating a potential for plant asphyxia. Other commonly reported factors that may affect growth of plants at landfill sites include the presence of trace toxic compounds in landfill gas and cover soil characteristics such as thickness, composition, compaction and moisture (15, 18).
2.10.6 Air Pollution Although methane and carbon dioxide are the two major components of the gas emitted from landfills; there is evidence that this gas contains numerous other constituents in trace amounts significant enough to cause environmental and health concerns. Potential emissions of volatile organic compounds (VOCs) from landfills can range from 4×10-4 to 1×10-3 kg / m2 / day. The presence of these chemicals in landfill gas can be attributed to regular household, co-disposal of light industrial wastes, or illegal dumping. Microbial investigations indicate that biodegradation by products within the landfill can also contribute to the formation of many of these chemicals. The primary concerns of trace gas emissions are air pollution and potential health hazards. The emission of VOCs is believed to have the potential to increase cancer risks in local communities and contribute to ambient ozone formation (15, 18).
27
2.10.7 Groundwater Contamination Landfill gas contains a high concentration of carbon dioxide which reportedly presents a significant groundwater pollution potential because of its high solubility. Furthermore, the emission of trace toxic gases within the landfill gas has been established to cause a serious threat to air and groundwater resources. Several examples are documented in the literature on the presence of vinyl chloride and other volatile hydrocarbons in groundwater at distances away from municipal landfills (15).
2.11
Other Impacts Associated with Landfills
2.11.1 Dust Problems Both main and access roads should be of all weather types, which should be sprinkled with water or another suitable dust control agent. Cover soils should be of a type not susceptible to wind erosion and final landfill cover should be planted. Wetting to control dust should be limited to the working zones within or near the landfill area.
2.11.2 Vectors The problem of vectors can be overcome by suitable soil cover. Rats and other mammalian vectors are discouraged from feeding on or propagating in solid waste which receives a well compacted 6 in soil layer of low clay content. This type of soil cover also discourages bird foraging; crows and seagulls which are especially likely to feed on uncovered solid waste. Flies – another potential vector – have difficulty when emerging from well compacted soil cover. Continuous grading of soil cover to fill in low spots is essential to prevent the development of stagnant pools of water in which mosquitoes can breed.
28
2.11.3 Noise and Aesthetics Routing vehicle traffic through industrial, commercial or low density population areas decreases the adverse noise impacts of landfill related vehicle traffics. Construction of noise barriers surrounding the landfill, such as earth barriers or walls is good practice and these with trees and planting can also improve landfill aesthetics. Litter fences, the prohibition of indiscriminate dumping outside the landfill, and the covering of old cars and trucks will keep the landfill site from becoming an eyesore. A clean, attractive gatehouse is a necessity. Access roads should be cleaned of litter periodically to improve site aesthetics.
2.11.4 Flood The potential for floods to increase the risk of contamination from landfills is obvious. The risks range from increased leachate production to a complete washout of landfill facilities. The destructive force associated with floods depends upon the depth, velocity and duration of the flood. The amount of debris in floodwater can significantly add to the erosion potential of floodwaters. Once contaminants enter surface waters, transport is generally rapid and the contaminants migrate rapidly to downstream waterways. Suspended contaminants tend to settle in slow moving portions of a river or stream or they may spread along the coast. This spread of contaminants can produce long term contamination problems that can adversely affect downstream water supplies and aquatic resources many years after the source of contamination has been removed. Contamination of surface waters by sediments can destroy aquatic organisms directly through toxic effects including food chain accumulation of low level concentrations (18).
29
2.11.5 Landfill Settlement Development of completed landfill sites is invariably hindered by significant settlements caused primarily by refuse decomposition which increases the void ratio and weakens the structural strength of the refuse within a landfill leading to a substantial loss of volume and settlement. Other causes of landfill settlement include: refuse dissolution into leachate, incomplete waste compaction, movement of smaller particles into larger voids created by biological and physico-chemical changes and subsurface fires, consolidation or mechanical compression due to the refuse thickness and own weight, or the load of construction material and structures erected on the landfill. The rate and magnitude of landfill settlement depends primarily on the refuse composition, operational practices and moisture content of the waste. It is estimated that the total settlement in a landfill ranges from 25 to 50% of the original thickness. Operational and load related settlements typically constitute 5 to 30% of total settlement and occur during landfill operations or shortly after closure. Long term settlements primarily due to refuse decomposition can theoretically reach 40% of the original thickness and occur gradually for several years after closure at a continually decreasing rate depending on stabilization processes within the landfill. On average; settlement of about 15% of total landfill thickness is expected due to waste decomposition. Landfills often exhibit great variations in waste composition resulting in nonuniform settlement patterns. This creates differential settlements which can have a devastating effect on the integrity of any structure erected on the landfill. Structural failures of buildings, surface cracks in the final cover, damage to the surface water drainage system, piping of leachate and gas collection systems, and underground utilities are commonly attributed to differential settlements. As well as variations in waste composition, changes in the manner in which the waste is placed or compacted, localized
30
raveling, vertical loads and subsurface fires can also contribute to differential settlements. Operational and maintenance practices (sorting, pretreatment, uniform compaction, etc.) can minimize problems associated with both total and differential settlements (15).
2.12
Risk Assessment The use of risk assessment as a tool in the decision making process has become
increasingly important over the last two decades as it has become evident that situations can not be judged simply as either safe or unsafe (27). Risk is a difficult concept to define; it is used in everyday language to mean chance of disaster. When used in the process of risk assessment it has a specific definition, the most commonly accepted being; the combination of the probability or frequency of occurrence of a defined hazard and the magnitude of the consequences of the occurrence. Or it is the process of estimating the potential impact of a chemical, physical, microbiological or psychosocial hazard on a specified human population or ecological system under a specific set of conditions and for a certain timeframe. It is a set of logical, systemic and well defined activities that provide complete information to risk managers, specifically policymakers and regulators and decision makers with a sound identification, measurement, quantification and evaluation of the risk associated with certain natural phenomena or man made activities, so that the best possible decisions are made (18, 27).
Risk assessment provides a systematic approach for characterizing the nature and magnitude of the risks associated with environmental health hazards. All activities, processes and products have some degree of risk. The ultimate aim of risk assessment is to provide the best possible scientific, social and practical information about the risks, so that
31
these can be discussed more broadly and the best decisions made as to what to do about them. Manifestation of risk requires an event, pathway for transport and a receptor which could be harmed at the exposure point. In essence, risk assessment provides a structured approach for ascertaining the nature and extent of the relationship between the cause and effect (27, 28). Good risk assessment is dependent on a high degree of scientific skill and objectivity and should be distinguished from the risk management process which selects options in response to health risk assessments that incorporates scientific, social, economic and political information and which requires value judgments on the tolerability of risk and reasonableness of costs. Risk assessment should provide a credible, objective, realistic and balanced analysis (27).
2.13
Health Risk Assessment Health risk assessment is the process of estimating the potential impact of a
chemical, biological, physical or social agent on a specified human population system under a specific set of conditions and for a certain timeframe (27).
2.14
Environmental Risk Assessment Environmental risk assessment is a process for estimating the likelihood or
probability of an adverse outcome or event due to pressures or changes in environmental conditions resulting from human activities. It involves identification, analysis and presentation of information in terms of risk to environmental values to inform planning and decision making processes. It does not
32
presume to provide all social and economic information relevant to making decisions, nor is the approach intended to planning and management processes (29).
2.15
Risk Assessment for Waste Disposal Sites The risks from waste disposal activities are in the nature of chronic human health
risks. The risk may be from exposure to toxic substances above a safe limit or from exposure from carcinogens for which a safe limit cannot be identified. Risk assessment activities in the waste disposal field are primarily undertaken by the regulatory agencies to develop prescriptive effluent standards. This is very much different from other industries such as nuclear and chemical where industry takes the initiative to assess the risk (30).
2.16
Public Perception of Waste Disposal Risk The public’s consciousness of the risk of waste disposal facilities has been greatly
raised during the past decade even with the limited risk assessment work that has been performed. Part of the increased public awareness has been due to the more extensive risk work on high profile wastes such as nuclear waste and the realization that there is much more than nuclear waste being put into the ground that contains toxic substances. The public lacks benchmarks for making scientifically based comparisons of different threats to their health and safety and the quality of the environment. The increased awareness of the public about the risks of waste disposal has an impact not only on pushing for improved disposal methods, but has probably made its greatest contribution on encouraging waste minimization (30).
33
2.17
Risk Assessment Models Although there has been reasonably aggressive in pushing risk assessment models,
there is still little application to solid waste disposal. The risk assessment work that is selectively performed in the waste disposal area is primarily based on deterministic models whose objective is to establish the migration of the contaminants from the source to the receptor by various pathways. These models do turn out to be quite complex. The deterministic analysis uses model parameter values that are at the central tendency of their distributions (usually the mean or the median). A second analysis uses model parameter values to predict the risks for those individuals whose exposure is above the 90th percentile of the population. Probabilistic analysis is used to account for parameter and model uncertainty and to quantify individual risk at selected percentiles of the risk distribution. The results are characterized as point estimates (central tendency and high end) as well as probabilistic (often the 50th, 90th, 95th, 97.5th and 100th percentiles) population risk estimates when the exposed populations are large and as individual risk estimates when the exposed populations are small. The risk estimates may be presented for different receptors; for example adults, children, residents, etc. (30).
2.18
Steps of Risk Assessment (3) Risk assessment takes place in four discrete steps; they are: 1. Hazard identification 2. Exposure assessment 3. Dose response assessment 4. Risk characterization
(3) Detailed description of each step is found in references (28 and 30) 34
2.19
Uncertainty of Risk Assessment While risk assessment is a rigorous scientific discipline, it has certain limitations. It
must be recognized that the present state of knowledge concerning the impacts of specific constituent is incomplete. Thus, each step in risk assessment involves uncertainty and it is important to make the best possible use of available information. In hazard identification, most assessments depend on animal tests and yet animal biological systems are different from human ones. In dose response, it is often unknown whether safe levels or threshold exists for any toxic chemical. Exposure assessment usually involves modeling, with the attendant uncertainty as to substance release, release characteristics, meteorology and hydrology. Because of these uncertainties associated with risk assessment; the exercise yields only an estimate of the risk and not the actual effect associated with a specific proposed or existing facility, so, the results of such an analysis should only be used as a guide in decision making (11, 27, 29). To compensate for uncertainties; worst case or reasonable worst case chemical exposures area assumed. The use of higher than expected exposure conditions emphasizes any potential problems and identifies potentially dangerous chemicals or sensitive exposure pathways for more detailed study (11). In most cases, this will result in overestimating the actual risks. A projected exposure level that exceeds an environmental or human health protection standard represents a warning flag, rather than an actual risk or effect (11).
2.20
Strengths of Environmental Risk Assessment 1. It is a mechanism that aids decision making especially the choice between options for risk reduction
35
2. It is a means of comparison between risks to determine whether there is equity of action or that the action is proportionate to the risk 3. It is a technique that can break down complex systems and identify areas of processes or plant where risk reduction options can be most effective 4. It builds an understanding of the relationships between the environment and human activity 5. It provides reassurance to stakeholders that potential changes to the environment due to human activities are being considered 6. It is valid scientifically, defensible and applicable (29)
2.21
Limitations of Environmental Risk Assessment (ERA) ERA will clarify risk to the environment from a decision, but it will not be able to
set an acceptable threshold of risk. Determining acceptable risk is an issue of risk management. Risk assessment is a basis for judgments about impacts but not for judgments on the acceptability of impacts. Decision makers must choose a desired or acceptable level of risk. ERA has the following limitations: 1. The use of scientific techniques such as risk assessment encourages an over reliance on and over confidence in the results. This is particularly focused at risk areas where there are great uncertainties and conservative approaches and safety factors are common. Those who query the certainty of the science will often claim that reliance on risk assessment based upon uncertain science is ill judged 2. Risk assessment focuses on parts of the problem rather than a whole. The most commonly performed risk assessments concentrate on single chemicals. Site specific risk assessments may examine a number of risks but each will be done
36
in isolation as the scientific data are not available for looking at mixture of agents yet 3. The relationship between risk assessment and management and the precautionary principle is somewhat awkward (29)
2.22
Previous Related Studies Dho et al. in 2000 predicted the leachate level in a landfill in Korea by total water
balance using the HELP model. The landfill received municipal solid waste, construction waste, water and sewage sludge and hazardous wastes. The average water content of the waste is 43.2 % with a maximum value of 55.9 % (by weight) in summer. The leachate level was high in this landfill, therefore; to get out the reason for the increasing leachate level, model calibration was carried out by HELP model to obtain the infiltration ratio of the landfill site using a leachate generation measured data. Analysis of the total water balance was carried out using the infiltration ratio obtained from the HELP results and then, a prediction of the leachate level in the future steps of disposal was made. The study concluded that the major causes of the elevation of the leachate level were the high water content of the waste and the degradation of the leachate drainage system caused by the subsidence of a natural barrier layer (32). Rimawi et al. 1999 studied the effect of solid waste disposal sites of the Greater Amman, Zarqa and Russiefeh area on the groundwater quality. Water quality monitoring was carried out using two groundwater wells in the surrounding area in the period of 1990 to 1995. Water samples as well as leachate were analyzed concluding that there were no actual signs indicating leachate migration from landfill sites to observation wells, but continuous monitoring in the area is highly recommended (33).
37
El-Naqa in 2004 attempted to assess aquifer vulnerability at Russeifeh solid waste landfill. The importance of this study was due to the location of this landfill on the most important aquifer in Jordan; Amman Wadi Sir. There is no system for collecting and treating the leachate generated at the bottom of the landfill. Therefore; the leachate infiltrates to the groundwater and degrades its quality. The study area is strongly vulnerable to pollution due to the presence of intensive agricultural activities, the solid waste disposal sites and industries. It was concluded that the groundwater at the site had a moderate vulnerability to contamination from the Russeifeh landfill (22). Nagar and Mirza in 2002 assessed the possible environmental impact of a landfill for the city of Jammu in India. The vulnerability of groundwater to contamination was quantified. The study revealed that the vulnerability of the aquifer contamination by leachate from the landfill is high and therefore concluded that; utilizing the liner technology of geo-synthetic clay materials and installing a drainage system to treat and collect leachate will mitigate this threat (34). Al-Yaqout in 2003 assessed the risk to groundwater associated with the unlined five landfills in Kuwait. These landfills receive various types of waste materials like sewage sludge, chemical waste, industrial waste, municipal solid waste and other debris. Large amounts of leachate are expected to be generated due to improper disposal methods even though the rain water is scarce. These landfills are not engineered facilities for the disposal of municipal solid waste as well as they are badly sited. Lack of proper design and operation will also adversely affect the environmental. The study – based on experimental scheme – outlined that all sites do not establish the minimum requirements for pollution control, although almost all sites are located not far from residential and commercial areas. One main concern is the possible contamination of the groundwater from leachate that contains high concentrations of organic compounds,
38
heavy metals, bacteria and viruses. These landfills have become breeding grounds for insects, mosquitoes and other disease causing vectors that may result in big epidemics at any time. The working conditions at these landfills are extremely dangerous for employees and residents nest to the sites. Bad odors have been noted by residents nearby the landfills. One of the simplest management systems suggested is the construction of lined evaporation ponds which are economic and safe solution (7). Qedisat in 2005 was concerned with modeling landfill gas generation from Ruseifeh landfill and assessing the environmental risk associated with it. This closed landfill is one of the unsanitary landfills in Jordan that has been established based on no specific design criteria. Moreover; the landfill does not have liner or leachate management system. Due to its proximity to urban centers and to its adverse environmental impacts, Ruseifeh landfill has been a subject of national debate, which leaded to the decision of landfill closure in the year 2003 (9). A landfill gas generation curve was developed for the closed Ruseifeh landfill using different modeling approaches with specific parameters of the landfill. Environmental risk assessment was conducted and outcome was: the risk level is acceptable for residential areas around the landfill while it is higher for workers and has unacceptable levels at the landfill site suggesting the need for risk management (9). Asia in 1999 studied the hazards associated with landfill gases considering methane and carbon dioxide. Methane is a colorless and odorless gas that has a low solubility in water and generally has little influence over groundwater quality. It occurs in gaseous form in the unsaturated zone. The gas, which causes asphyxiation, is highly flammable and can be explosive (35). Carbon dioxide is colorless, odorless, and non-combustible. This gas also causes asphyxiation. A concentration of 3% (v/v) in air can cause headaches and difficulty in
39
breathing to human beings. Symptoms become severe at concentration above 5% (v/v) and unconsciousness can result at 10% (v/v). Concentrations above 15% (v/v) may be fatal. LFG migration can be a dangerous hazard because of the combustible and in some cases explosive nature of the methane; and also the asphyxiant nature of the carbon dioxide (35). Methane is less dense than air, and carbon dioxide is denser than air. A gas containing 54% methane and 46% carbon dioxide is nearly as dense as air. Therefore, LFG can be more or less as buoyant as air, depending on its composition. Consequently, it is dangerous to assume that LFG will always rise. When it is denser than air it can accumulate at low levels and persist unless forced to move through air movements or pressure build-up (35). A review of literature by Vrijheid in 2000 showed an increase of reports of adverse health effects by people living near landfill sites. This includes: 1. Increase in self reported health outcomes and symptoms such as headaches, sleepiness, respiratory symptoms, psychological conditions, gastro-intestinal problems, excesses in bladder, lung and stomach cancers reported 2. Adverse pregnancy outcomes such as low birth weight and increased risk of birth defects 3. Increased presence of chromosomal changes; especially in children (36).
40
CHAPTER THREE STUDY AREA
3.1 Location and Site Description Al-Akaider Landfill is located in the northern region of Jordan, near the main road to Mafraq Governorate. It is a part of the Irbid and Mafraq Governorates; located in the boundaries of Al-Yarmouk Watershed with Palestinian coordinates of 251° 22’ E and 216° 33’ N, Figure 3.1. It is located at 27 km to the east of the city of Irbid, just at a distance of 1 km from the Syrian borders. It can be reached by a paved road about 7 km to the north of the Irbid-Mafraq highway. The nearest village is about 1.58 km to the south west called Al-Akaider village. This site was chosen because of low population density, low land cost and to minimize the leakage of contaminants into groundwater. Nowadays; the area near the landfill becomes populated and the impacts of the landfill on the public health and the surrounding environment should be investigated (38, 38, 39). Solid waste deposition in this landfill was started in 1981. A study conducted in 1987 stated that; it was intended to close the landfill after 15 operational years, i.e. in 2003, but solid waste is still deposited up to date
(6, 38)
. Based on an interview with the
manager of Al-Akaider landfill site; it is expected to close the landfill in 2020 as it will reach its full capacity by that time.
41
Yarmouk River
North Rift Catchment Area
Jordan Rift
Syria Irbid
Ramtha Al-Akaider Landfill Yarmouk Basin
Sama Es Sarhan
Nueimeh Al-Akaider Village Um Ejmal
Ajlun Dead Sea
Amman Zarqa Basin
Figure 3.1: Location of Al-Akaider Landfill (38)
Al-Akaider landfill is the only official dump site for northern Jordan with an area of 806 × 103 m2 used in almost equal proportions for the disposal of industrial wastewater and municipal solid waste, see Figure 3.2. It serves the inhabitants of Irbid city and another 62 villages and cities in Irbid, Mafraq, Jarash and Ajloun Governorates. Although by far the largest disposal site in the northern Jordan, Al-Akaider is not the only one. It is however believed to be the only site in the region that accepts liquid wastes. Municipal solid waste, small quantities of industrial waste and industrial wastewater are disposed at the site. In the past; municipal wastewater was discharged with the industrial wastewater, nowadays; municipal wastewater is discharged directly to a new treatment plant near the landfill (6, 38, 39, 40).
42
Figure 3.2: Al-Akaider Landfill Layout (40) 3.2 Climatic Conditions 3.3.1
Rainfall, Temperature and Solar Radiation Generally; the climate of Jordan is of East Mediterranean type; identified as being
hot and dry in summer and cold and humid in winter. The US Environmental Agency has classified regions into arid and non-arid regions based on rainfall of 12.5 in/yr (312.5 mm/yr) to be the reference. The area is classified as an arid region since the average annual rainfall is about 6.3 in / yr (160 mm / yr), see Figure 3.3. The nearest meteorological station to Al-Akaider landfill is Khanasira at a latitude of 32 ° 24’ N and longitude 36 ° 03’ E (9, 42). Annual rainfall is statistically investigated following a best fit of normal distribution as shown in Figure 3.4 with an average of 159.82 mm and standard deviation of 52.07. To check the goodness of fit, the Chi Square (χ2) is calculated, the sum of the χ2
43
values is 11.3; this means the confidence is greater than 95 % (43). R2 value of 98.95 % also supports this fit. The highest mean annual temperature is 27.43 °C, while the lowest mean annual temperature is 8.70 °C, see Figure 3.5 and 3.6. The average annual solar radiation for the study area is about 18 MJ / m2 / day, see Figure 3.7. 270 250
Annual Rainfall (mm)
230 210 190 170 150 130 110 90 70 50 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Figure 3.3: Total Annual Rainfall in the Study Area (42) 1 0.9
Cumulative Probability
0.8
2
R = 0.9895
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 50
70
90
110
130
150
170
190
210
230
250
270
Annual Precipitation (mm)
Figure 3.4: Frequency Function for Normal Distribution Fitted to Annual Precipitation 44
Temperature (oC)
30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Figure 3.5: Average Annual Maximum Temperature in the Study Area (42)
15 14 13 12
o
Temperature ( C)
11 10 9 8 7 6 5 4 3 2 1 0 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Figure 3.6: Average Annual Minimum Temperature in the Study Area (42)
45
21 20
18
2
Solar Radiation (MJ/m /day)
19
17 16 15 14 13 12 11 10 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Figure 3.7: Average Annual Solar Radiation in the Study Area (42) 3.3.2
Relative Humidity The relative humidity is defined as the ratio of the actual vapor pressure at a given
point to its saturation value at a given air temperature
(43)
. When the relative humidity is
unity, this means that the atmosphere is fully saturated with water vapor. In an arid country like Jordan, it is expected that the relative humidity will be high in the wet winter and low in the dry summer. Table 3.1 summarizes the seasonally relative humidity data for the study area. By referring to Table 3.1; it is recognized that relative humidity values in summer are higher than those in the spring. This may be due to the presence of the industrial wastewater ponds therefore, the evaporation rate in summer is higher than that in the spring and hence the relative humidity values are expected to be higher.
46
Table 3.1: Seasonally Relative Humidity for the Study Area (%) (42)
3.3.3
Year
Winter
Spring
Summer
Autumn
1983
81.00
54.00
57.33
64.33
1984
66.33
48.33
53.00
69.00
1985
75.00
56.00
61.33
70.21
1986
70.67
52.00
59.67
73.00
1987
68.67
45.67
55.67
68.33
1988
76.00
47.00
56.33
67.33
1989
71.00
40.67
55.00
63.67
1990
70.33
43.67
52.33
50.67
1991
68.33
43.67
54.33
64.33
1992
74.67
47.00
51.00
63.45
1993
71.67
51.00
61.67
69.00
1994
80.67
51.33
62.00
75.67
1995
73.67
47.67
57.67
63.67
1996
74.33
48.67
57.67
70.33
1997
76.67
51.67
60.67
71.00
1998
78.47
53.10
55.40
61.27
1999
72.57
58.40
65.93
59.77
2000
77.00
51.00
63.33
69.00
2001
68.80
50.80
67.90
74.57
2002
75.13
65.97
60.53
64.80
Wind Speed and Direction Wind speed and direction are important factors that affect the dispersion and
concentration of pollutant / chemical in the nearby areas of the landfill. To show the information about the distributions of wind speeds and the frequency of the varying wind directions; a site wind rose was developed based on meteorological data of wind speed and wind directions
(9)
. Figure 3.8 is a standard wind rose of the study area based on available
monthly data; it was drawn using the wind rose plotter software while Table 3.2 summarizes the average wind speed and the prevailing wind direction. For each of the sectors the outermost (blue) wedges show the wind frequency distribution. The middle (black) wedges show the distribution of the product of the wind 47
speeds times their frequency. The innermost (red) wedges show the distribution of the wind speeds cubed (i.e. the energies) multiplied by their frequencies (44).
Figure 3.8: Wind Rose of the Study Area (1992 – 2002) Table 3.2: Average Wind Speed and the Prevailing Wind Direction (42) Year
Wind Speed (km/h)
Direction
Year
Wind Speed (km/h)
Direction
1983
8.9
-
1993
9.3
258.3 o
1984
9.2
-
1994
9.8
257.3 o
1985
9.3
-
1995
9.3
281.9 o
1986
7.5
-
1996
9.6
261.8 o
1987
8.2
-
1997
9.1
246.3 o
1988
7.8
-
1998
8.8
272.8 o
1989
6.8
-
1999
8.4
270.7 o
1990
7.2
-
2000
8.2
260.6 o
1991
9.1
-
2001
6.8
253.3 o
1992
10.2
264.2 o
2002
9.2
264.2 o
Time series of the average monthly values of the previous climatic data (precipitation, relative humidity, wind speed and temperature) are presented in Figure 3.9 to see the trend of each all over the year.
48
80
45
40
75 35
Relative Humidity (%)
Precipitation (mm)
70 30
25
20
15
65
60
55 10
50
5
0
45 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Month
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
A: Average Monthly Precipitation (mm)
B: Average Monthly Relative Humidity (%)
12.0
27 25
11.0 23 21 o
Mean Temperature ( C)
Wind Speed (km/Hr)
10.0
9.0
8.0
7.0
19 17 15 13 11 9
6.0 7 5
5.0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Nov
Dec
Month
Month
C: Average Monthly Wind Speed (km/Hr)
D: Average Monthly Temperature (°C) 34
18
32
16
Mean Maximum Temperature ( oC)
o
Mean Minimum Temperature ( C)
30
14
12
10
8
6
4
28 26 24 22 20 18 16 14
2
12 10
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Month
Month
E: Average Monthly Minimum Temperature (°C)
F: Average Monthly Maximum Temperature (°C)
Figure 3.9: Average Monthly Climatic Data (42) 3.3 Topography The topography of the study area may be described as a mix between hilly and semi-flat about 650 m above the sea level. This site is located in a natural wadi that had a
49
gradient of approximately of 2 to 3 % falling from east to west, later turning towards the north west. The land on both sides of the wadi rises with a gradient of more than 12 %. It is not readily possible at present to determine the eventual flow of wadi water through the site due to the continuing activities of solid waste disposal and lagoon construction (38, 39). 3.4 Hydrogeology and Soil Characteristics The aquifer system in the study area is considered as a confined aquifer. The depth of the saturated zone is located at 330 to 450 m below the ground surface. The piezometric head of the confined aquifer in the study area is about 400 m above the mean sea level (38). The effective vertical hydraulic conductivity in the study area ranges from 3.18 × 10-6 m / sec to 8.86 × 10-5 m / sec. Also, the high moisture absorbency of the aquifer should be taken in consideration since it includes chalk, marl, chalky limestone, thin beds of chert, phosphate and bituminous chalk, Figure 3.10 (38, 39).
7m
Thickness
Log
Top Soil Chalky limestone with cherl intercalation. Marly limestone
63 m
Chalky marl. Marl. Bituminus marl
230 m
SWL 333 m Chalky marl. Limestone. Chert with marly limestone
184 m
Limestone with dolomitic limestone
114 m
Figure 3.10: Geologic Cross Section of the Study Area (38)
50
Previous studies for the engineering soil classification at Al-Akaider landfill site stated that the soil can be categorized as silty soil with sand (5). The hydraulic conductivity for different soil types (coarse and fine soils) is listed in Table 3.3. Table 3.3: Hydraulic Conductivity based on Soil Description (41) Soil Type
Hydraulic Conductivity (m / sec)
Gravel
10-2
Gravel and Sand Mixtures
10-5
Sand –Silt Mixtures
10-9
Clay
10-11
3.5 Landfilling Practice at Al-Akaider Landfill Al-Akaider landfill was designed unsanitary; neither leachate collection system nor gas collection and removal system is used at all in the landfill. The waste is currently being tipped in a large excavation. The available soil at site – mainly sandy silty soil – is used to cover the waste at the end of each operational day (39). Thickness of the daily cover ranges from 30 cm to about 90 cm according to the weight of the compaction truck used. A study performed in 1987 about the landfilling practice in Al-Akaider landfill stated that the method used was in place combustion followed by spreading as shown in Figure 3.11. Solid waste was combusted in piles, after which the residues of combustion were removed and spread on the site (6).
51
Figure 3.11: In Place Combustion of Solid Waste, 1987 (6)
Nowadays; open burning is cancelled due to its harmful impacts on the surrounding environment. The method of landfilling is: the solid waste is firstly spread, compacted using trucks and bulldozers and finally covered with the daily cover material, see Figure 3.12 (40).
Figure 3.12: Municipal Solid Waste Compaction at Al-Akaider Landfill 52
Also, the site is used for the disposal of sludge and liquid waste from dairy, slaughter houses and dying industries. The liquid waste is carried by truck tankers to the disposal site. In some places of the disposal site the liquid waste was mixed with the solid waste as shown in Figure 3.13, but this practice was finally eliminated (6).
Figure 3.13: Liquid Waste Disposal at Al-Akaider Landfill, 1987 (6)
Some families live just beside Al-Akaider landfill to earn their living by working at the landfill via contracts with some local companies. They (sons, daughters, wives and their husbands) used to separate metals, copper, plastics and cans from the solid waste piles. In September 2005, children of ages less than 15 years old were prohibited to enter the landfill site. This practice (recycling work) is only restricted to adults. Figure 3.14 outlines this practice (40).
53
Figure 3.14: Solid Waste Separation at Al-Akaider Landfill 3.6 Impacts and Problems of Al-Akaider Landfill Site 1. Landfills are considered Locally Undesirable Land Uses (LULU) therefore values of the property in the proximity of the landfill site are decreasing. Landlords adjacent to Al-Akaider landfill site have suffered from losses of their property values. 2. Disposal of the highly contaminated wastewaters should be performed in a controlled manner that minimizes the adverse impacts on the human health and the environment. The practice of wastewater disposal at Al-Akaider landfill has adversely affected the plants and trees after relatively short time since it contains high concentrations of chemicals. Figure 3.15 illustrates dry trees that are affected by the highly polluted industrial wastewater disposed at Al-Akaider landfill.
54
Figure 3.15: Dry Trees Affected by Industrial Wastewater
3. Landfills have to be bordered to prevent the travel of papers and plastic bags to the surrounding areas as well as the passage of animals into / out from the landfill. Also, the soil cover layer has to be applied at the end of each operational day. For Al-Akaider landfill site; the blowing winds in the absence of the daily cover and landfill border caused plastic bags to travel long distances reaching the nearby farms which resulted in the death of 150 goats. Compensating value of 13, 000 JD was paid. 4. Earthen dams that are constructed to store wastewater have to be strong enough otherwise they will be destroyed due to the excess water pressure. If this occurs; the surrounding areas will be contaminated as happened at Al-Akaider landfill in 2000. 5. It is known that the landfill gas, rich in methane, is a flammable and explosive gas when presented in a ratio of 5 – 15 % by volume. Therefore it is common to notice fires and explosions at MSW landfills. For Al-Akaider landfill, two huge fires were recently reported, 2004 and 2005, due to the presence of methane gas (40).
55
3.7 Waste Composition and Quantities Precise information on the waste composition disposed at the landfill is not available. Though, a study conducted in 2001 showed that the landfilled waste is mostly organic. Figure 3.16 represents the composition of solid waste disposed at Al-Akaider landfill. Others; 3 Metals; 2 Glass; 2 Fiber; 2 Paper; 17
Food Waste; 63
Plastic; 11
Figure 3.16: Composition of Solid Waste Disposed at Al-Akaider Landfill (5)
Food waste has the highest percentage of total waste with percentage of 63 % while paper has the second highest percentage of 17 %. About 20 % of the waste is nondegradable materials. Industrial waste portion is about 10 % of the waste disposed at the landfill (5, 40). The number of population served by Al-Akaider landfill was obtained from the Department of Statistics for the years from 1994 to 2004 (45). These statistics were fitted to a straight line resulting in value of R2 of 0.9942 and hence the population for the coming years was estimated. The per capita generation rate of municipal solid waste in Jordan ranges from 0.72 to 0.91 kg / capita / day. This range includes the increase of solid waste generation as a result of life changes
(5, 39)
. Since there are no records regard the amounts of solid waste
disposed at Al-Akaider, researchers tried to estimate the waste quantity as a range (upper and lower limits). In 1987, Abu Qdais expected the daily per capita generation of
56
municipal solid waste; his expectation ranged from 0.78 to 0.92 kg/capita/day; which was reasonable and close to that found in References 5 and 9. Estimated solid waste quantities to be disposed at Al-Akaider landfill are tabulated in Table 3.4.
Table 3.4: Estimated Annual Quantity of SW Disposed at Al-Akaider Landfill Year
Population
SW Quantity (ton) L. L.
U. L.
U. L.
2001
944683
243269
316250
2002
969543 **
248569
323140
192232
2003
994402
**
253869
330030
199122
2004
1023400 **
259169
336919
206012
2005
1035102
*
264469
343809
212902
2006
1055846 *
269769
350699
2007
1076589
*
275068
357589
1097332
*
280368
364479
1118075
*
285668
371369
2010
1138818
*
290968
378259
2011
1159562 *
301568
392038
254241
2012
1180305
*
306868
398928
261131
2013
1201048 *
306868
398928
2014
1201048
*
317468
412708
1242534
*
322767
419598
1263278
*
328067
426488
2017
1284021
*
333367
433377
2018
1304764 *
338667
440267
302470
2019
1325507
*
343967
447157
309360
2020
1346250 *
349267
454047
537266
137271
178452
1982
558009 *
142571
185342
1983
578752
*
147871
1984
599495 *
153171
1985
620238
*
158470
1986
640982 *
163770
1987
661725
*
682468
*
703211
*
1990
723954
*
184970
240461
1991
744698 *
190270
247351
1992
765441
*
195570
1993
786184 *
200870
1994
808094
**
827734
**
849207
**
1997
870680
**
222070
288690
1998
892153 **
227369
295580
1999
915470
**
232669
2000
921737 **
237969
1989
1995 1996
174370 179670
206169 211470 216770
219791 226681
2008
233571
2009
268020 274911
2015
281801
2016
L.L. = Lower Limit (Based on 0.72 kg/capita/day generation rate) U.L. = Upper Limit (Based on 0.91 kg/capita/day generation rate) *
Estimated by the Researcher
**
SW Quantity (ton) L. L.
1981
1988
Population **
*
169070
Year
Actual Population
57
CHAPTER FOUR RISK ASSESSMENT OF INDUSTRIAL WASTEWATER PONDS AND LEACHATE AT AL-AKAIDER LANDFILL 4.1 Introduction In this chapter, the risk associated with the industrial wastewater ponds and AlAkaider landfill leachate will be assessed based upon the results of different models. Four models will be used to perform this task. The first two models will be used for the industrial wastewater ponds risk assessment while the other two models are utilized to assess the risk associated with Al-Akaider landfill leachate. The models are: 1. Green-Ampt model to estimate the time required for a conservative contaminant at the industrial wastewater (IWW) to reach the groundwater table 2. Contaminant transport model to study the transport of nitrate (NO3-) under the IWW ponds at the site and to develop the breakthrough curves (BTC) 3. Hydrologic Evaluation of Landfill Performance (HELP 3) model to quantify the amount of leachate generated from solid waste at Al-Akaider landfill 4. Seasonal Soil Compartment Model (SESOIL) to study the transport of nitrate from Al-Akaider landfill leachate to the subsurface soil layers
These models are interrelated together such that the output of certain model is a primary input of another. Figure 4.1 outlines the procedures followed to assess the risk associated with IWW ponds to the groundwater at Al-Akaider landfill site.
58
Industrial Wastwater Ponds
Development of BTC By the Contaminant Transport Model
Arrival Time Estimation By Green-Ampt Model
Verification By Analyzing GW Samples
Risk Assessment
Risk Management
Figure 4.1: Procedures of IWW Ponds Risk Assessment 4.2 Green-Ampt Model 4.2.1
Introduction Infiltration is the process of water penetration from the ground surface into soil.
Many factors influence the infiltration rate, including; the condition of the soil surface and its vegetative cover, the properties of soil; such as its porosity, hydraulic conductivity and the current moisture content. Soil strata with different physical properties may overlay each other, forming horizons; for example, a silty soil with relatively high hydraulic conductivity may overlay a clay zone of low conductivity. Also, soils exhibit great spatial variability even within relatively small areas. As a result of these great spatial variations and the time variations in soil properties that occur as the soil moisture content changes, infiltration is a very complex process that can be described only approximately with mathematical equations (43).
59
Green-Ampt model is based on Darcy type water flux. Infiltration has to be proportional to the total gradient including the soil suction head
(46)
. Green-Ampt model
governing equations are:
F (t ) F (t ) = Kt + (Ψ − ho ) ln1 + (Ψ − ho )∆θ
.............................. (4.1)
(Ψ − ho )∆θ f (t ) = K 1 + F (t )
.............................. (4.2)
Where; K
= the hydraulic conductivity (m/day)
ho
= initial depth of water in the pond (m)
ψ
= soil suction head (m)
∆Ө
= porosity – moisture content (vol. / vol.)
t
= time (day)
F(t) = the cumulative infiltration (m) f(t)
4.2.2
= the infiltration rate (m/day)
Green-Ampt Model Solution Green-Ampt model will be utilized to calculate the infiltration rate of a
conservative contaminant from the IWW ponds at Al-Akaider landfill site to the subsurface soil layers. Knowing the values of the hydraulic conductivity (K), soil suction head (ψ) and the difference between the porosity and the moisture content (∆Ө); the cumulative infiltration F(t) can be calculated. The value of F(t) can be substituted in Equation 4.2 to determine the corresponding potential infiltration rate f(t). The average head (ho) of wastewater at the pond is about 6.5 m. Equation 4.1 can be solved by Newton's iteration method, which is more complicated than the method of successive substitution and converges in less iterations. A code utilizing this technique was developed to solve such equation. Specific Green-Ampt infiltration parameters for Al-Akaider landfill site are summarized in Table 4.1, while the
60
infiltration rates and arrival times for the three soil layers (see Figure 3.3) beneath the wastewater ponds at different soil moisture contents are summarized in Tables 4.2 and 4.3. Table 4.1: Green-Ampt Infiltration Parameters at Al-Akaider Landfill (22, 38, 40, 43) Parameter
Soil Layer # (1)
Soil Layer # (2)
Soil Layer # (3)
63
230
33
0.864
0.029
0.864
Wastewater Head (m)
6.5
0.0
0.0
Suction Head (m)
0.05
0.316
0.05
Porosity (vol. / vol.)
0.41
0.385
0.41
2 – 38
2 – 38
2 – 38
Thickness (m) Hydraulic Conductivity (m/day)
Initial Moisture Content (%)
Table 4.2: Infiltration Rate of the Soil Layers at Different Moisture Contents Moisture Content (%)
Infiltration Rate (m / day) Layer # (1)
Layer # (2)
Layer # (3)
2
4.057
0.034
0.880
5
4.290
0.033
0.879
10
4.681
0.032
0.876
15
5.051
0.031
0.874
20
5.421
0.030
0.872
25
6.441
0.030
0.871
30
6.462
0.029
0.868
35
6.483
0.029
0.866
38
6.681
0.029
0.865
61
Table 4.3: Arrival Time of the Soil Layers at Different Moisture Contents Moisture Content (%)
Arrival Time (days)
Total (years)
Layer # (1)
Layer # (2)
Layer # (3)
2
15.53
6782.66
37.51
18.73
5
14.69
6936.28
37.56
19.15
10
13.46
7181.44
37.65
19.82
15
12.47
7390.98
37.74
20.39
20
11.62
7584.00
37.83
20.91
25
9.78
7754.55
37.89
21.38
30
9.75
7897.00
38.01
21.77
35
9.72
8013.94
38.10
22.09
38
9.43
8058.86
38.15
22.21
From the previous results, one can notice that as the soil moisture content increases; the infiltration rate decreases and hence the arrival time increases. This is due to the soil suction head effect which is of its maximum value when the soil is dry and demolishes gradually as the soil becomes saturated. This is not valid for the first soil layer, because the water head effect is the dominant infiltration driving force other than the soil suction head. When calculating the arrival time based on Darcy's law and assuming the gradient as a unit and the soil is fully saturated; the arrival time is 22.41 years which is close to those in Table 4.3 especially the last two values when the soil is approximately saturated. Therefore, the infiltration results and arrival times obtained by the Green-Ampt model and those obtained by the Darcy's law are approximately the same. These results will be used in solving the contaminant transport model and developing breakthrough curves as presented in the following section.
62
4.3 Contaminant Transport under IWW Ponds 4.3.1
Theoretical Background One of the greatest threats of waste releases is the contamination of groundwater
supplies. Pollutants released from landfills, ponds and underground storage tanks have sometimes migrated through the unsaturated zone to the groundwater where they have reached drinking water wells or other receptors. Calculation of the subsurface contaminant transport is a difficult process because it is based upon the characteristics of the substrata and the velocity of the flowing contaminant as well as the degree of sorption, transformation, reaction and biodegradation. Therefore, it is important to differentiate between a conservative and non-conservative contaminant. The general equations used to model contaminant transport, in both saturated and unsaturated conditions, are given below: C ( x, t ) 1 = {exp( A1 ) × erfc( A2 ) + exp(B1 ) × erfc(B2 )} Co 2
.............................. (4.3)
Where; A1 = A2 = B1 = B2 =
x 2 v' x − (v' x ) + 4 D ' x k ' 2D'x x −t
.............................. (4.4)
(v' x )2 + 4 D' x k '
.............................. (4.5)
2 D' x t x v' x + 2D'x x+t
(v' x )2 + 4 D' x k '
.............................. (4.6)
(v' x )2 + 4 D' x k '
.............................. (4.7)
2 D' x t
D ' x = Dx / R
.............................. (4.8)
v' x = v x / R
.............................. (4.9)
k'= k / R
.............................. (4.10)
63
R = 1+
ρB Kd θ
.............................. (4.11)
C = Contaminant Concentration (mg/l) Co = Initial Contaminant Concentration (mg/l) x = Distance (m) t = Time (days) Dx = Dispersion Coefficient in X-Direction (m2/day) vx = Flow Velocity in X-Direction (m/day) k = Decay Rate (day-1) R = Retardation Factor Kd = Soil Distribution Coefficient (ml/g) Ө = Soil Moisture Content (vol. / vol.)
It is clear from the previous equations that the rate of change of a contaminant concentration at any point down gradient is a function of not only the advective and dispersive transport, but also the first order degradation rate. These equations may be utilized as a tool to estimate the time required for a relative contaminant concentration to reach a certain distance down gradient. However, another effective use is to develop a contaminant concentration profile as a function of distance at a set time or as a function of time at a set distance (47).
4.3.2
Analysis of IWW arriving at Al-Akaider Landfill The industrial wastewater disposed at the site comes from different sources
including; dairy, slaughterhouses, dying industry and sludge. Different samples were obtained from trucks arriving at the site and then analyzed. Results of analysis are tabulated in Table 4.4. It is recognized that these types of wastewater are very rich in chemicals and have a very high nitrate concentration as compared to municipal wastewater.
64
Table 4.4: Analysis of Wastewater Arriving at Al-Akaider Landfill Slaughterhouse
Dairy
Dying Industry
Chicken
Wastewater
Wastewater
Wastewater
Sludge
19
19.1
20.4
19.20
pH
7.12
4.11
6.9
6.33
EC (mS/cm)
1.839
29.7
2.54
4.46
Total Solids (mg/L)
3465
31042.5
1862.3
-
Total Dissolved Solids (mg/L)
3168.3
30215.83
1272.3
-
Total Suspended Solids (mg/L)
296.67
826.67
590
-
Total Volatile Solids (mg/L)
3424.7
30328.3
1788.3
-
40.3
714.2
74
-
273.37
393.7
560
-
23.3
433.33
30
-
3151.33
29934.6
1228.3
-
Fixed Dissolved Solids (mg/L)
17
280.87
44
-
Dissolved Oxygen (mg/L)
0.9
0.6
2.4
0.1
811.6
3468
256.6
-
BOD5 (mg/L)
640
29950
5
-
COD (mg/L)
4790
104200
680
-
NO3- (mg/L)
740
4260
1900
-
Parameter Temperature (ºC)
Total Fixed Solids (mg/L) Volatile Suspended Solids (mg/L) Fixed Suspended Solids (mg/L) Volatile Dissolved Solids (mg/L)
Turbidity (NTU)
4.3.3
Contaminant Transport and Breakthrough Curves Contaminant transport process was studied and breakthrough curves were
developed by solving Equation 4.3. Three soil layers were considered; see Table 4.1 and Figure 3.3. The velocity of flow was changed according to the soil moisture content (refer to the Green-Ampt model solution, Table 4.2). The contaminant to be considered in this study is nitrate (NO3-) which is a conservative material and therefore, the retardation factor will be unity. Also, all forms of nitrate are soluble in water, this means that the nitrate will move with the same velocity of water. The breakthrough curves of each soil layer at different soil moisture contents are outlined in Figures 4.2 to 4.4. By referring to Figure 4.2 it is clear that the transport process is very fast since the soil is considered as sand (high hydraulic conductivity) and
65
the depth of the industrial wastewater (IWW) at the pond is 6.5 m which is the driving force of flow through this layer. The second layer is categorized as silt and hence the transport process is relatively slow, Figure 4.3. Most of the time of the transport process is consumed within this layer because it has the lowest hydraulic conductivity (3.3 × 10-7 m/sec) and the largest depth (230 m). The third layer is sand and has a depth of 33 m, so, the rate of transport is relatively high, Figure 4.4, but is slower than that of the first layer even though they have the same hydraulic conductivity. This is mainly due to the lack of industrial wastewater head effect. This indicates that the second layer may be considered as the controlling layer at the site since most of the arrival time of the contaminant is spent in this layer. It is concluded that the transport of nitrate under the IWW ponds will take approximately 22 years to reach and eventually contaminate the groundwater at AlAkaider landfill. Al-Akaider landfill site has been receiving IWW since 1981, so, according to the results of the contaminant transport model; the groundwater is contaminated by nitrate (and may be other chemicals) as a result of the random disposal process of the industrial wastewater.
66
100
90
Normalized Concentration (C/Co)
80
70 2% 5% 10% 15% 20% 25% 30% 35% 38%
60
50
40
30
20
10
0 9
9.5
10
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
15.5
16
Time (days)
Figure 4.2: Breakthrough Curves of Nitrate at the 1st Soil Layer and Different Moisture Contents
100
90
80
Normalized Concentration (C/Co)
2% 70
5% 10%
60
15% 20%
50
25% 30%
40
35, 38 %
30
20
10
0 6400
6550
6700
6850
7000
7150
7300
7450
7600
7750
7900
8050
8200
Time (days)
Figure 4.3: Breakthrough Curves of Nitrate at the 2nd Soil Layer and Different Moisture Contents 67
100
90
Normalized Concentration (C/Co)
80
70 2% 5% 10% 15% 20% 25% 30% 35% 38%
60
50
40
30
20
10
0 36.8
37
37.2
37.4
37.6
37.8
38
38.2
38.4
38.6
38.8
Time (days)
Figure 4.4: Breakthrough Curves of Nitrate at the 3rd Soil Layer and Different Moisture Contents
To verify the obtained results; the groundwater flow direction was obtained from Reference 38 and groundwater flow maps of the study area and then water samples were obtained from two wells (one of them is upstream while the other is down stream). The upstream well is located at a distance of about 1.5 km from the landfill while the down stream is about 5 km far from the landfill. The samples were analyzed and the results of analysis are summarized in Table 4.5. By referring to Table 4.5; one can conclude that the plume of the contaminant has spread and therefore groundwater contamination from the industrial wastewater ponds at Al-Akaider landfill has already occurred. Concentration of the dissolved solids downstream is higher than that upstream. Electrical conductivity is also higher indicating that ions' concentration downstream is higher than that of the upstream. The percent increase of nitrate concentration downstream taking the upstream value as a reference is
68
about 31.7 % and both of them are less than the maximum contaminant level specified by the World Health Organization (50 mg/L). The Jordanian standards (JS No. 893/2002) specify the maximum concentration of nitrate in drinking water as 30 mg/L. It is expected that the concentration of nitrate will increase and may exceed the threshold value in the future since high concentrations of nitrate are migrating to the groundwater at the site. Turbidity and suspended solids concentration downstream is less than that upstream; this may be due to the filtration process that clarifies water when flowing downstream.
Table 4.5: Analysis Results of Drinking Water Samples Parameter
Upstream
Downstream
Temperature (ºC)
20.1
20.5
pH
7.44
7.25
EC (µS/cm)
863
1077
Total Solids (mg/L)
460
570
Total Dissolved Solids (mg/L)
185
316
Total Suspended Solids (mg/L)
275
254
Alkalinity (mg/L) as CaCO3
266
309
Hardness (mg/L) as CaCO3
320
428
Dissolved Oxygen (mg/L)
9.00
5.98
Turbidity (NTU)
11.29
6.72
6.3
8.3
-
NO3 (mg/L)
The primary function of the following sections is to estimate the leachate quantity discharged at Al-Akaider landfill, to study the transport of nitrate from leachate to the subsurface soil layers and to assess the risk associated with Al-Akaider landfill leachate to the groundwater at the site. Figure 4.5 outlines the procedures followed to perform these tasks.
69
Estimation of Leachate Quantity By HELP MODEL
Analysis of Leachate Sample
Transport of Nitrate By Using SE-SOIL Model
Breakthrough Curves
Arrival Time
Verification By Analyzing GW Samples
Risk Assessment
Risk Management
Figure 4.5: Procedures of Al-Akaider Landfill Leachate Risk Assessment 4.4 HELP Model 4.4.1
Model Description The US EPA's HELP Model is by far the most widely used tool to predict leachate
quantity and analyze water balance in landfill lining and capping systems
(48)
. It is a quasi
two dimensional hydrologic model of water movement across, into, through and out of landfills. HELP generates estimations of runoff amounts, evapotranspiration, drainage, leachate production and leakage from liners. HELP model was developed to help hazardous waste landfill designers and regulators to evaluate the hydrologic performance of proposed landfill designs (49). The model accepts weather, soil and design data and uses solution techniques that account
for
the
effects
of
surface
storage, 70
snowmelt,
runoff,
infiltration,
evapotranspiration, vegetative growth, soil moisture storage, lateral subsurface drainage, leachate recirculation, unsaturated vertical drainage, and leakage through soil, geomembrane or composite liners. Landfill systems including various combinations of vegetation, cover soils, waste cells, lateral drain layers, low permeability barrier soils and synthetic geo-membrane liners may be modeled. The program was developed to conduct water balance analyses of landfills, cover systems and solid waste disposal and containment facilities (49). The primary purpose of the model is to assist in the comparison between design alternatives as judged by their water balances. The model, applicable to open, partially closed and fully closed sites, is a tool for both designers and permit writers (49).
4.4.2
Concepts behind HELP Model HELP model uses many process descriptions that were previously developed and
reported in the literature and used in other hydrologic models. For example: Runoff modeling is based on the Soil Conservation Service (SCS) curve number method. Potential evapotranspiration is modeled by the modified Penman method. Evaporation of interception and surface water is based on the energy balance method. Interception is modeled by the method proposed by Horton. Vertical drainage is modeled by Darcy’s law. Saturated lateral drainage is modeled by an analytical approximation to the steady state solution of the Boussinesq equation. Evaporation from soil, plant transpiration and vegetative growth were extracted and modeled using the methods included in Simulator for Water Resources in Rural Basins (SWRRB) model. These processes are linked together in a sequential order starting at the surface with a surface water balance; then evapotranspiration from the soil profile and finally drainage and water routing, starting at the surface with infiltration and then proceeding downward
71
through the landfill profile to the bottom. The solution procedure is applied repetitively for each day as it simulates the water routing throughout the simulation period (49).
4.4.3
Input Data Generally; data to be used in modeling must be as accurate as possible. Data
required by HELP model can be summarized in Table 4.6.
Table 4.6: Input Data Required by HELP Model (21, 49) Data Type
Parameter Evaporative Zone Depth
Weather Data
Landfill Characteristics
Soil and Solid Waste Data
Unit
Time Step
cm
-
Maximum Leaf Area Index
-
-
Relative Humidity
%
Seasonally
km / hr
-
Rainfall Data
mm
Daily
Temperature Data
°C
Average Wind Speed
Daily 2
Solar Radiation
MJ/m
Daily
Landfill Area
Acres
-
%
-
Runoff Curve Number
-
-
Layer Type and Texture
-
-
Layer Thickness
in
-
m / sec
-
vol. / vol.
-
% of Landfill where Runoff is Possible
Hydraulic Conductivity Porosity, Moisture Content, Field Capacity and Wilting Point
Average values of temperature, annual rainfall, and solar radiation data were presented in Chapter 3. Soil Data was obtained from borehole logs at the landfill site to a depth of 333 m below the ground surface, see Figure 3.3. Data concerning solid waste was obtained from site visits to Al-Akaider landfill and other necessary data are reported by Qian et al. 2002 and Schroeder et al. 1994. HELP model input parameters are summarized in Tables 4.7 – 4.9.
72
Table 4.7: HELP Model Input Parameters Parameter Evaporative Zone Depth Maximum Leaf Area Index Wind Speed Relative Humidity Annual Rainfall Temperature Solar Radiation Runoff Curve Number
Range
Typical Value
Source
4 – 60 in
24.6 in
-
0–5
0.85
51
1.7 – 17.1 km / hr
8.2 km / hr
42
69 – 73 %
-
42
-
160 mm
42
12 – 27 ºC
-
42 2
-
18 MJ/m /day
42
75 – 85
83
43, 52
Table 4.8: Properties of Solid Waste Disposed at Al-Akaider Landfill Parameter
Range
Typical Value / Average
Source
-
15
40
Porosity (vol. / vol.)
0.40 – 0.67
0.67
21, 49
Field Capacity (vol. / vol.)
0.22 – 0.55
0.292 / 0.224
21, 49
Wilting Point (vol. / vol.)
0.019 – 0.17
0.084
21, 49
0.05 – 0.3
0.2
21, 49
-
40 Hectare
40
10-2 – 5×10-5
10-3
21, 49
Thickness (m)
Initial Moisture (vol. / vol.) Landfill Area (for solid waste disposal) Hydraulic Conductivity (cm/sec)
Table 4.9: Properties of Soil at Al-Akaider Landfill Site Parameter
Range
Typical Value / Average
Source
-
3
38
Total Thickness (m)
300 – 450
333
38
Porosity (vol. / vol.)
0.39 – 0.501
0.41
43, 49
Field Capacity (vol. / vol.)
0.05 – 0.418
-
21, 49
Wilting Point (vol. / vol.)
0.02 – 0.367
-
21, 49
-
22
Number of Soil Layers
Hydraulic Conductivity (m/sec)
-6
3.18 × 10 - 8.86 × 10
73
-5
4.4.4
Simulation and Results HELP was run using 22 years (1981 – 2002) daily climatic data for the study area.
The landfill was modeled using three layers (from bottom to top); the barrier soil layer, the compacted solid waste layer and the soil cover layer, the soil used for cover is silty soil with sand that is available at the site. Results of the simulation including leakage/percolation, the average head on the top of the barrier soil layer and volume of leakage through the barrier soil layer are presented in Table 4.10. Annual leachate volumes generated at the barrier soil layer are plotted in Figure 4.6. By referring to the rainfall records of the study area, Figure 3.4, it may be noticed that the rainfall in the years 1994 and 1997 are approximately the same while the generated leachate quantities are different. This is due to the difference between rainfall intensities in these years and this will affect the results of runoff. Another reason is that the rainfall quantity in 1996 is twice that in 1993 and model takes into account the preceding years in estimating the generated leachate quantity.
Table 4.10: Available Leachate Head & Leakage through the Barrier Soil Layer Year
Leakage (mm)
Head (mm)
Leakage (m3)
1981
8.31
0.01
3363.28
1982
22.61
0.02
9148.97
1983
5.45
0.01
2206.16
1984
0.23
0.0
93.75
1985
27.20
0.021
10993.83
1986
2.32
0.0
940.13
1987
10.80
0.01
4368.80
1988
40.78
0.033
16504.21
1989
0.12
0.0
49.18
1990
17.54
0.014
7099.70
1991
1.23
0.0
495.85
1992
67.13
0.053
27166.20
74
Table 4.10: Available Leachate Head & Leakage through the Barrier Soil Layer (cont.) 1993
0.01
0
2.26
1994
0.12
0.0
48.29
1995
0.26
0.0
106.76
1996
0.07
0.0
27.76
1997
20.41
0.02
8259.04
1998
15.84
0.014
6408.30
1999
2.33
0.0
944.42
2000
21.64
0.02
8758.43
2001
16.94
0.013
6856.60
2002
21.23
0.02
8592.70
Average
13.75
0.012
5565.21
St. Dev.
16.43
0.013
-
28 26 24
Leachate Volume (103 m3)
22 20 18 16 14 12 10 8 6 4 2 0 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year
Figure 4.6: Annual Leachate Volume Generated at Al-Akaider Landfill as Estimated by HELP Model Water budget components at the end of each simulation year including rainfall, evapotranspiration, runoff, change of water storage are also included in the output of the
75
simulation and are illustrated in Table 4.11. Table 4.12 outlines the average and the standard deviation of monthly values of water budget components at Al-Akaider landfill site. Other results are tabulated in Tables 4.13 – 4.14.
Table 4.11: Water Budget Components at Al-Akaider Landfill (1981 – 2002) Leakage
Head
∆S
(mm)
(mm)
(mm)
121.71
8.31
0.010
0.02
14.22
132.48
22.61
0.020
8.09
162.7
2.90
171.49
5.45
0.010
-17.14
1984
187.9
2.80
177.48
0.23
0.000
7.39
1985
196.3
22.56
129.62
27.20
0.021
16.92
1986
179.2
11.76
162.72
2.32
0.002
2.40
1987
123.1
5.18
119.60
10.80
0.010
-12.48
1988
239.3
17.62
161.13
40.78
0.033
19.77
1989
114.4
1.15
139.72
0.12
0.000
-26.59
1990
151.9
8.39
141.10
17.54
0.014
-15.13
1991
190.4
8.03
138.35
1.23
0.001
42.79
1992
271.6
69.70
150.56
67.13
0.053
-15.79
1993
73.9
0.72
80.65
0.01
0.000
-7.48
1994
205
5.61
189.10
0.12
0.000
10.17
1995
79
0.50
107.50
0.26
0.000
-29.26
1996
142.4
0.62
124.98
0.07
0.000
16.73
1997
208.6
26.52
164.15
20.41
0.020
−2.48
1998
139.4
9.44
136.85
15.84
0.014
-22.73
1999
60.3
0.28
40.09
2.33
0.002
17.60
2000
168.8
14.73
126.35
21.64
0.020
6.08
2001
129.7
9.00
110.47
16.94
0.013
-6.71
2002
179.2
39.22
135.72
21.23
0.020
-16.97
Average
159.82
12.57
134.63
13.75
0.012
-1.13
St. Dev.
52.07
16.06
32.82
16.43
0.013
17.91
100
7.86
84.24
8.60
-
-0.70
Year
P (mm)
RO (mm)
ET (mm)
1981
135.6
5.56
1982
177.4
1983
% of Rainfall
P = Precipitation RO = Runoff ET = Evapotranspiration Head = Depth of Leachate at the Bottom of the Landfill ∆S = Change in Water Storage St. Dev. = Standard Deviation
76
Table 4.12: Average Monthly Values of Water Budget Components P (mm)
RO (mm)
ET (mm)
Leakage (mm)
Month
Avg.
St. Dev
Avg.
St. Dev
Avg.
St. Dev
Avg.
St. Dev
January
46.65
29.77
4.75
8.95
18.97
13.57
1.84
4.85
February
45.87
37.12
6.07
12.07
34.96
12.1
5.03
7.85
March
23.77
19.65
0.56
1.70
26.82
15.98
4.76
6.15
April
4.66
5.24
0.07
0.19
13.36
8.17
1.67
2.23
May
1.05
3.47
0.0
0.0
10.40
1.90
0.30
0.62
June
0.00
0.00
0.0
0.0
10.67
2.44
0.04
0.07
July
0.00
0.00
0.0
0.0
5.51
4.91
0.0
0
August
0.00
0.00
0.0
0.0
1.23
2.42
0.0
0
September
0.00
0.00
0.0
0.0
0.44
1.15
0.0
0
October
4.10
6.39
0.004
0.01
0.61
0.70
0.0
0
November
14.83
20.28
0.55
1.64
4.18
8.41
0.001
0.01
December
18.89
21.07
0.57
1.74
7.47
10.52
0.10
0.43
Table 4.13: Average Annual Totals for Years 1981 through 2002 Value (mm)
St. Dev
Volume (m3)
% Value
Precipitation
159.82
52.07
64679.40
100
Runoff
12.57
16.06
5085.85
7.86
Evapotranspiration
134.63
32.82
54482.73
84.24
Leakage
13.75
16.43
5565.21
8.6
Available Head
0.011
0.013
-
-
∆S
-1.12
0.71
-454.41
-0.70
Component
Table 4.14: Peak Daily Values for Years 1981 through 2002 Value (mm)
Volume (m3)
Precipitation
53.00
214448.81
Runoff
15.10
6103.21
Leakage
2.48
1004.36
Available Head
0.66
-
Component
77
4.4.5
Discussion Since Al-Akaider landfill is located in an arid region (rainfall is less than 25 in /
year), the leachate quantity (both percolated and accumulated) is expected to be relatively small. The average annual depth of leachate generated at Al-Akaider landfill for the simulation period (1981 – 2002) is 13.75 mm, so, the average annual leachate volume is 5565.21 m3 (0.01375 m × 400 ×103 m2). It can be observed that the major component of the water budget is the evapotranspiration with a yearly average of 134.63 mm and accounting for 84.24 % of rainfall. The average surface runoff accounts for 7.86 % whiles the remaining 8.6 % are accounting for the average leakage/leachate discharged. Since the study area is characterized by a high evapotranspiration (pan evaporation = 3000 mm / year) and low rainfall (160 mm / year), the water budget may be negative in some years especially those have low rainfall records. Chopra et al., 2001 simulated the leachate generation at Al-Akaider landfill using HELP model. Results of the simulation indicated that the leachate volume generated at the barrier soil layer was extremely low (or even zero) for the prevailing climatic conditions (5)
. This is in contrast with the results of our study even though both of them were
performed by using the same software. The reason for this disagreement is their use of default daily climatic data of Nevada rather than Jordan. Also, the simulation period, five years, is relatively small and therefore the results can not be generalized in that manner. During one of the site visits, the discharged leachate was observed; a sample was taken and then analyzed (Section 4.5). Abu Qdais et al., 2006 utilized HELP model to simulate leachate generation in an arid landfill in Rafah, Gaza Strip. In their study, they pointed out; in arid regions the most significant factors affecting leachate generation are the evaporative zone depth and the
78
maximum leaf area index. The typical range for the evaporative zone depth was 50 to 65 cm while it was 0.45 – 1.65 for the maximum leaf area index. They outlined that the best prediction of leachate was obtained when the evaporative zone depth was 60 cm and the maximum leaf area index was 0.85 (51). Since both Al-Akaider and Rafah landfills are: •
Located in arid regions
•
Not planted after closing cells / portion of the landfill
•
Still receiving municipal solid waste
•
Containing solid waste with almost the same composition (high organic and moisture contents)
The same methodology, procedures and reasonable site specific assumptions based upon engineering judgment were used. So, values of the maximum leaf area indices for the two landfills are identical (0.85). For Al-Akaider landfill site, the evaporative zone depth value is 62.5 cm, which is slightly greater than that of Rafah landfill (60 cm) due to the higher annual evaporation and lower relative humidity values at Al-Akaider landfill site.
4.4.6
Sensitivity Analysis The aim of the sensitivity analysis is to present how the sensitive parameters will
affect the results of the simulation process. Abu Qdais et al., 2006 revealed that the maximum leaf area index (MLAI) and the evaporative zone depth (EZD) were the most significant parameters affecting leachate quantity in arid regions. It was noted that a small change in any of them will dramatically affect the modeled leachate quantity (51). The change of the maximum leaf area index taking the optimum value (0.85) as a reference will affect the simulation results as shown in Figure 4.7. It is noted that increasing the maximum leaf area index will reduce the leachate quantity and vice versa.
79
This is logical since increasing the maximum leaf area index will increase the plant cover; hence increasing the evapotranspiration and therefore the leachate quantity will decrease. Also, increasing the evaporative zone depth means that water will be evaporated from deeper soils and therefore the leachate quantity will decrease, which makes sense, Figure 4.8. The same results but with different percentage were reached by Abu-Qdais et al., 2006 (51)
.
8
6
% Change in Leachate Quantity
4
2
0 0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
-2
-4
-6
-8 Change in the Maximum Leaf Area Index about the Optimum Value
Figure 4.7: Effect of Changing the M.L.A.I. on Leachate Quantity
80
1.3
50.00
40.00
% Change in Leachate Quantity
30.00
20.00
10.00
50
51
52
53
54
55
56
57
58
59
60
61
0.00 62
63
64
65
66
67
68
69
70
71
72
73
74
75
-10.00
-20.00
-30.00
-40.00 Change in the Evaporative Zone Depth about the Optimum Value (cm)
Figure 4.8: Effect of Changing the E.Z.D. on Leachate Quantity 4.5 Composition of Leachate Produced at Al-Akaider Landfill Site In the previous sections, the amount of leachate and the available head on the top of barrier soil layer have been obtained and outlined. To know how strong the leachate is, a quality test is to be performed. Leachate sample was collected from Al-Akaider landfill site and subjected for analysis. The obtained sample has a dark black color and a very bad strong odor that causes headache. Air bubbles were also noticed at the leachate sample. Quality characteristics of leachate sample are presented in Table 4.15.
81
Table 4.15: Characteristics of Leachate Sample from Al-Akaider Landfill Parameter
Value
Temperature (ºC)
19.4
pH
7.25
EC (mS/cm)
38.2
Total Solids (mg/L)
3482
Total Dissolved Solids (mg/L)
2642
Total Suspended Solids (mg/L)
840
Total Volatile Solids (mg/L)
1468
Fixed Suspended Solids (mg/L)
560
Volatile Dissolved Solids (mg/L)
1188
Fixed Dissolved Solids (mg/L)
1454
Volatile Suspended Solids (mg/L)
280
Alkalinity (mg/L) as CaCO3
608
Dissolved Oxygen (mg/L)
0.25
Turbidity (NTU)
2178
BOD5 (mg/L)
17800
COD (mg/L)
43850
NH3 as N (mg/L)
2800
NH3 (mg/L)
3400
-
NO3 as N (mg/L)
80
NO3- (mg/L)
358
It is clear from Table 4.15 that the BOD5 and COD of leachate are about 100 times stronger than wastewaters and dissolved solids' concentration is high. So, it is important to study the transport of certain pollutants at leachate to the subsurface and then to assess the risk of groundwater contamination. The pollutant to be considered in this study is nitrate because it is of special concerns due to its harmful effects on the human health (especially the babies) at low concentrations and causes cancer at concentrations higher than 150 mg/L. Also, it is a conservative material that is neither adsorbed to soil nor volatilized into soil air and all forms of nitrate are soluble. The SESOIL model will be utilized to perform this task.
82
4.6 SESOIL Model 4.6.1
Model Description SESOIL is a transport model that helps in modeling the contaminant transport and
concentrations into the unsaturated soil zones. It is a one dimensional vertical transport model. Typically, it is used to estimate the rate of migration of chemicals through the soils and the concentration of chemicals in the soil layers following chemical release to the environment. The different phases in which the contaminant may exist are also modeled. The pollutant cycle in SESOIL includes the convective transport, volatilization, adsorption / desorption and degradation / decay. In SESOIL the soil compartment is a cell extending from the surface through the unsaturated zone to the upper level of the saturated soil zone (groundwater table). The soil column is broken into several layers as well as the layer can be divided up into 10 sub layers having the same soil properties as the layer in which they reside. While SESOIL estimates the contaminant concentration added to the groundwater, the saturated zone is not modeled. The output of SESOIL can be used for generating input values for the saturated zone contaminant transport models (53).
4.6.2
Concept behind SESOIL SESOIL focuses on the various chemical transport and transformation processes
which occur in the soil. These processes include percolation, volatilization, diffusion, degradation, hydrolysis and metal complexation. The actual quantity or mass of pollutant taking part in any one process depends on the competition among all the processes for the available pollutant mass. Pollutant availability for participation in these processes and the pollutant rate of migration to the groundwater depends on its portioning in the soil among the gas (soil air), dissolved (soil moisture) and solids (adsorbed to soil) phases.
83
In SESOIL, any layer or sub-layer can receive pollutant, store it and export it to other sub-compartments. Downward movement of the pollutant occurs only with the soil moisture while the upward movement can occur by vapor phase diffusion. The pollutant cycle is based on a mass balance equation (Equation 4.12) as follows:
Ot −1 + I t = Tt + Rt + M t
………………………… (4.12)
Where; Ot-1 = Amount of pollutant originally in the soil column at time t-1 (µg/cm2) It = Amount of pollutant entering the soil column during time step (µg/cm2) Tt = Amount of pollutant transferred within the soil column at time step (µg/cm2) Rt = Amount of pollutant remaining in the soil column at time t (µg/cm2) Mt = Amount of pollutant migrating out of the soil column during the time step (µg/cm2)
The fate of the pollutant in the soil column includes both transport and transformation processes, which depend upon the chemical partitioned among the three phases; the soil air, the soil moisture and the soil solids. The concentration in the soil air is calculated via the modified Henry's law stated in Equation 4.13.
C sa =
cH R (T + 273)
………………………… (4.13)
Where; Csa = Pollutant concentration in soil air (µg/ml) c = Pollutant concentration in soil water (µg/ml) H = Henry's law constant (m3.atm/mol) R = Universal gas constant [8.2 × 10-5 (m3 × atm)/(mol × ºK)] T = Soil temperature (ºC)
84
The concentration adsorbed to the soil is calculated using the Freundlich isotherm as stated in Equation 4.14. S = K d c1 / n
………………………… (4.14)
Where; S = Pollutant adsorbed concentration (µg/g) Kd = Pollutant portioning coefficient (µg/g)/(µg/ml) c = Pollutant concentration in soil water (µg/ml) n = Freundlich exponent
The total concentration of the pollutant in the soil is computed as stated in Equation 4.15. Co = f a × C sa + θ × c + ρ b × S
………………………… (4.15)
Where; Co = Overall pollutant concentration (µg/cm3) fa = (f-θ) = the filled air porosity (ml/ml) f = Soil porosity (ml/ml) θ = Soil moisture content (ml/ml) 3 ρb = Soil bulk density (g/cm )
The pollutant cycle equations are formulated on a monthly basis and the results are given for each simulated month. However, to account for the dynamic processes in the model accurately; an explicit time step of one day is used in the equations. The monthly output represents the summation of results from each day (53).
85
4.6.3
Input Data Data required by the SE-SOIL model including the climatic data, soil data,
pollutant data and application data are presented in Table 4.16
Table 4.16: Input Data of SE-SOIL Model (53) Data Type
Parameter
Unit
Time Step
Degree
-
Rainfall
cm
Monthly
Temperature
°C
Monthly
Relative Humidity
%
Monthly
Cloud Cover
%
Monthly
Number of Storms
-
Monthly
Latitude of the Site
Climatic Data
Layer Depth
cm
Intrinsic Permeability Soil Data
cm
Bulk Density
g / cm
-
meq / 100 g
-
vol. / vol.
-
Water Solubility
mg / l
-
Adsorption Corfficient
ml / g
-
cm2 / sec
-
m . atm / mole
-
-
-
Porosity
Air Diffusion Coefficient 3
Henry's Law Constant Valence Molecular Weight
g / mole
Biodegradation Rate
Application Data
Year
-1
-
Number of Soil Layers and Sub Layers
-
-
Pollutant Initial Concentration in Soil
mg / kg
-
Pollutant Initial Concentration in Rain
mg / l
-
Continuous
Years
Pollutant Loading Characteristics
4.6.4
3
Cation Exchange Capacity
Pollutant Data
-
2
Simulation and Results SESOIL was simulated using the available climatic data (presented in Chapter 3)
for the study area. Since the maximum layer thickness modeled by SESOIL is 99.99 m and the maximum number of layers to be simulated is three in addition to the contaminant
86
layer; the soil profile was divided into three layers with a total depth of 300 m instead of 333. The concept of equivalent hydraulic conductivity was utilized to obtain the effective hydraulic conductivity of each of the three soil layers. The contaminant to be studied is nitrate which is a conservative material and therefore it will travel with the same velocity as water (As stated earlier). The model was calibrated such that the arrival time of a conservative contaminant from the industrial wastewater ponds at the site to the groundwater is about 20.5 years. By referring to the Green Ampt model solution; it can be observed that this time will be obtained when the soil moisture content is between 15 and 20%. This value of the soil moisture content was chosen because it is the intermediate value between the two extremes (dry and saturated conditions). The results of model calibration are presented on monthly and annual basis in Figures 4.9 and 4.10 respectively.
40
80
120
320
360
400
440
480
-100 -200 -300
Depth (m)
0.0
0
Time (Months) 160 200 240 280
Figure 4.9: Calibration of a Conservative Material Depth versus Time in Months
87
0.0
5
10
25
30
35
40
-200 -300
Depth (m)
-100
0
Time (Years) 15 20
Figure 4.10: Calibration of a Conservative Material Depth versus Time in Years
Leachate quantity was obtained from the results of HELP model while the quality data were obtained from laboratory results. This data was fed to the SESOIL and the results of simulation including the arrival time of nitrate based on monthly and annual basis are outlined in Figures 4.11 and 4.12 respectively. It can be observed that the arrival time of nitrate from Al-Akaider landfill leachate to the groundwater is about 23 years which is slightly greater than that of the industrial wastewater ponds. This is due to the low leachate quantity as compared to the industrial wastewater that has a depth of 6.5 m. The breakthrough curve of dissolved nitrate is presented in Figure 4.13. It is clear that nitrate will exit from the unsaturated zone and then enter the saturated zone after about 23 years indicating that the contamination of groundwater by leachate has already taken place. By referring to Figure 4.13 one may conclude that the concentration of nitrate entering the saturated zone in the year 2006 (after 25 years of operation) is about 70 mg/l. This concentration will increase in the near future reaching a maximum value of 358 mg/L (Co) when the age of the landfill is about 40 years (in 2021). The concentration of nitrate in groundwater down gradient will be less than 358 mg/L due to the dilution process taking
88
place when the highly concentrated pollutant is mixed with the groundwater and the groundwater quality will be degraded with time. Since nitrate is a conservative material; the adsorbed and volatilized concentrations are zero.
5
10
25
30
35
40
-300
Depth (m) -200 -100
0.0
0
Time (Years) 15 20
Figure 4.11: Nitrate (NO3-) Depth versus Time in Years Time (Months) 40
80
120
160
200
240
280
320
360
400
440
-100 -200 -300
Depth (m)
0.0
0
Figure 4.12: Nitrate (NO3-) Depth versus Time in Months
89
480
400 300 200 100 0.0
Dissolved Concentration (mg/L)
0
10
20
30
40 50 60 Time (Years)
70
80
90
100
Figure 4.13: Average Annual Dissolved Concentration vs. Time at 300 m Depth
4.6.5
Discussion The outcome of the simulation process supports the notion that the groundwater at
Al-Akaider landfill region is being contaminated by leachate and the industrial wastewater ponds. The effect of leachate on the groundwater quality will clearly appear in the near future. This result is compared with that obtained by Chopra et al. 2001 and it seems that there is a contrast between the two results. The reason for this mismatch is their use of climatic data of Nevada due to the lack of site specific data during their study. Their study also revealed that the need for leachate collection system in Jordan is not urgent and that the contamination risk to groundwater from leachate is not significant (5). The contamination of groundwater at the area is an evidence that the leachate collection system is necessary even if the landfill leachate quantity is relatively small and the groundwater depth is large. One may conclude that the contamination of groundwater
90
is only a matter of time and leachate will eventually reach the groundwater and will degrade its quality. The result of the study performed by El-Naqa in 2004 on assessing the aquifer vulnerability at Russeifeh landfill stated that leachate infiltrates to the groundwater and degrades its quality. The soil type at the area is classified as sandy loam while the aquifer media is limestone. The study concluded that the Russeifeh landfill area is strongly vulnerable to contamination due to the presence of landfill leachate (22). This is in harmonic with the results obtained in this study indicating that the same trend coincides in two of the most important landfills in Jordan even though the soil layers and thicknesses are different. Al-Adamat et al. 2003 studied the groundwater vulnerability for the basaltic aquifer of the Azraq basin of Jordan. The area has been subjected to permanent settlement and significant agricultural expansion since the early 1990s. The groundwater depth in the area ranges from 233 to 466 m and the soil type is a mix between silty loam and clayey loam. DRASTIC model was utilized in their study and they revealed that about 84% of the study area was classified as being at moderate risk while the remainder 16% was classified as low risk (54). The groundwater at Azraq basin is at risk from the use of fertilizers in agricultural activities even though its depth is large. Imagine what would happen to the groundwater if a continuous discharge of leachate or industrial wastewater is taking place. Actually; the situation will be worse and this supports the output of our study. Samanraja and Bandara in 2005 investigated groundwater quality close to landfill sites in the Colombo Metropolitan Region (CMR). The groundwater depth is less than 10 m, therefore it is a shallow aquifer. The water quality parameters selected for the study were BOD, COD, nitrate, phosphate and levels of some heavy metals. Analysis showed that in some wells located around the landfill; the concentration of some heavy metals
91
exceeded the standards set by the Central Environmental Authority (CEA) for inland water quality. It can be concluded from this study that the groundwater sampled in the study are contaminated with heavy metals, organic matter, nitrates and phosphates. Since the quality of the wells closest to the landfills are the worst it can also be concluded that leachate from landfill sites significantly affects the groundwater quality (55).
4.7 Risk Assessment and Management of IWW Ponds and Leachate Nitrate, which is a non-carcinogenic chemical, will be used in the risk assessment task. It is a pollutant that has a reference dose of 1.6 mg/kg/day and the exposure route is ingestion. Nitrates level in excess of 150 mg/L poses an extreme risk to infants' health in the form of blue baby syndrome. Moreover, high nitrates may have carcinogenic effects for adults (56, 57). The downstream concentration will be used in calculations. The risk for adults can be calculated as follows: I=
CW × IR × EF × ED BW × AT
I = Daily intake (mg / kg.day) CW = Contaminant Concentration (mg / L)
[8.3 mg / L]
IR = Ingestion Rate(L/ day)
[2 L/ day for adults]
EF = Exposure Frequency(days / year)
[365 days / year]
ED = Exposure Duration (years)
[30 years ]
BW = Body Weight (kg)
[70 kg]
AT = Averaging Time(days)
[70 years ]
I = 0.474(mg / kg.day ) Risk = HI =
Acceptable
I 0.474 = = 0.296 RfD 1.60
92
The risk for (children) infants of body weight of 10 kg and ingestion rate of 1 L/day can be calculated as follows: I=
CW × IR × EF × ED BW × AT
I = Daily intake (mg / kg.day) CW = Contaminant Concentration (mg / L)
[8.3 mg / L]
IR = Ingestion Rate(L/ day)
[1 L/ day for adults]
EF = Exposure Frequency(days / year)
[365 days / year]
ED = Exposure Duration (years)
[30 years ]
BW = Body Weight (kg)
[10 kg]
AT = Averaging Time(days)
[70 years ]
I = 1.659(mg / kg.day ) Risk = HI =
Un-acceptable
I 1.659 = = 1.037 RfD 1.60
It is recognized that the risk value is acceptable for adults while it is un-acceptable for children. This is due to the fact that the daily intake value is normalized to the body weight and the immunity of children is weak in comparison with adults. The risk value will increase in the future since high concentrations of nitrate are migrating to the groundwater. Water may be un-suitable for irrigation purposes due to the presence of other chemicals or pollutants unless suitable management and treatment options are taken. Monitoring wells both upstream and downstream should be installed to analyze the groundwater samples periodically and hence to suggest the possible uses of such waters.
93
CHAPTER FIVE GASEOUS EMISSIONS AND RISK ASSESSMENT OF AL-AKAIDER LANDFILL
5.1 Introduction Some models are principally structured to describe the trend of landfill gas generation. They are quantitative summary of the important processes that take place in the system. Landfill gas models are established either to forecast the generation rate of biogas or to evaluate the potential gas problems to both the human health and the environment. Most of the models used to estimate landfill gas generation are consistent since most of the landfills have the same gas generation approach. The majority of the models predicting landfill gas generation are based upon either the multiphase or the single phase first order kinetics. The primary goal of this chapter is directed towards environmental and health risk assessment of the gaseous emissions of Al-Akaider landfill. Two models will be used to perform this task. The first is the Gas-Siam (multiphase gas generation model) to quantify the landfill gas and hence to assess the associated risk, while the second is Land-Gem (single phase gas generation model) to verify the results of Gas-Sim model, see Figure 5.1
5.2 Gas-Sim Model Gas-Sim is a tool used to model landfill gas generation. It considers the landfill as a one unit. The model is probabilistic with the exception of the atmospheric dispersion module. The model is divided into four main parts; they are: •
Source term
94
•
Emissions model
•
Environmental transport
•
Exposure / impact (58)
HELP Model
Quantity of
Gas-Sim Model
Landfill Leachate
Estimation of Landfill Gases
Verification of Results By Land-Gem Model
Risk Assessment
Risk Management
Figure 5.1: Schematic Diagram Presenting the Relationship between Models 5.2.1
Concept behind Gas-Sim The biodegradation of organic material is carried out by a multi-phase first order
decay equation that deals with the three degradable fractions separately and aggregates the amount of carbon converted to LFG. The rates of decay and degradation half lives are dependent on the waste moisture content; a wet waste will degrade at a faster rate than a dry one. The gas generation is determined using a multi-phase first order LFG generation equation, developed by the HELGA framework. The Gas-sim multi-phase equations can: •
Define the mix (breakdown), composition and moisture content of waste in the landfill site
•
Calculate LFG generation based on the degradation rates of the individual materials 95
in the landfilled waste. These features make the Gas-sim multi-phase equation highly flexible and allow it to be modified to individual landfill sites, taking account of specific waste streams, filling / deposition rates and environmental conditions (58). The governing equations are:
[
Ct = Co − Co ,1e − k1t + Co, 2 e − k 2t + Co , 2 e − k3t
]
………………………… (5.1)
C x = Ct − Ct −1
………………………… (5.2)
Where; Ct
= Mass of degradable carbon degraded up to time t (Mg)
Co
= Mass of degradable carbon at time t = 0 (Mg)
Co,1 = Mass of degradable carbon at time t = 0 in each fraction (1,2,3,rapidly, moderalty & slowly) (Mg)
5.2.2
Cx
= Mass of carbon degraded in year t (Mg)
t
= Time between waste emplacement and LFG generation (yr)
ki
= Degradation rate constant for each fraction of degradable carbon (yr-1)
Data Required Data required by Gas-Sim including solid waste data, landfill characteristics and
climatic data are summarized in Table 5.1.
96
Table 5.1: Data Required by Gas-Sim Model (58) Data Type
Parameter
Unit
Time Step
Ton
Yearly
Quantity Composition
-
Cellulose Decay Rates Solid Waste Data
Year
Moisture Content
Soil Data Climatic Data
5.2.3
-
Waste Density
3
Ton / m
-
Porosity
vol. / vol.
-
m
-
m / sec
-
Hydraulic Conductivity Characteristics and
-
%
Leachate Head Landfill
-1
2
Landfill Area
m
Soil Layer Thickness
m
-
m / sec
-
mm
Yearly
Hydraulic Conductivity Rainfall
Al-Akaider Landfill Gas Generation Landfill gas generation is simulated from 1981 to 2055. The trend of the simulation
follows the triangular model theory. In the period from 1981 to 2021; the methane generation increases as well as the waste input quantities. After the year of 2021, the landfill is assumed to be reaching its full capacity and will be closed; hence the methane generation rate will decrease. This can be interpreted as: the landfill enters a stage of stabilization where methanogenic bacteria starts to produce less methane amounts due to low moisture content and low fresh biodegradable solid waste. Since Gas-Sim input data is probabilistic (the model accepts data as probability distribution or as a range). The most sensitive parameters of the Gas-Sim model are the cellulose decay rates. Since there is no calibration due to the lack of real measurements; the cellulose decay rates were obtained from previous studies (one of them were conducted on a Jordanian landfill) and fitted to a probability distribution before being entered to the
97
software. Methane generation results for different confidence intervals (5 % to 95%) are outlined in Figure 5.2. Gas-Sim model is capable of simulation the methane production for 100 years. However; methane generation has been estimated to a period of 35 years after the closure of the facility. The waste input quantity for the study period was entered to the model as a range to account for the uncertainty.
Methane 2,200
1 Year after the closure
2,000
1,800
Gas Generated (m3/hr)
1,600 1,400
1,200
1,000 800
600
400 200
0
1985
1990
1995
2000
5% Less Than 90% Less Than
2005
2010
2015
10% Less Than 95% Less Than
2020 Year
2025
25% Less Than
2030
2035
2040
50% Less Than
2045
2050
2055
75% Less Than
Figure 5.2: Gas-Sim Methane Generation Results (1981 – 2055) 5.3 Land-Gem Model Land-Gem model uses a simpler approach since it follows the single phase first order decay rate. It determines the mass of methane generated using the methane generation capacity and the mass of carbon deposited. The quantity of LFG generated is
98
determined using the methane generation capacity and the proportion of methane to carbon dioxide. The quantity of LFG generation capacity is then used to determine the amount of carbon available for degradation (Equation 5.4). The LFG generation is then determined using the amount of carbon available for degradation and the methane generation rate (Equation 5.6). 1 L % CH 4 / 100 L1 = M Vm
………………………… (5.3)
C = C1 × L1
………………………… (5.4)
Ct = Co − (Co,1e − kt )
………………………… (5.5)
C x = Ct − Ct −1
………………………… (5.6)
Where; L1
= Landfill gas generation capacity (g/Mg)
Vm
= Molar volume at STP (2.241 × 10-2 m3 mol-1)
M
= Relative molecular mass of carbon (mol/g)
L
= Methane generation capacity (m3/Mg)
% CH4 = Percentage of methane within raw landfill gas C
= Mass of carbon available to degrade (Mg)
C1
= Mass of waste deposited (Mg or tones)
Ct
= Mass of degradable carbon degraded up to time t (tones)
Co
= Mass of degradable carbon at time t = 0 (tones)
Cx
= Mass of carbon degraded in year t (tones)
t
= Time between waste emplacement and LFG generation (years)
k
= Methane generation rate (per year) The decay equation 5.6 only determines quantity of available carbon, which is used
to determine the generation of methane and carbon dioxide, the proportion of which can be determined using the methane to carbon dioxide ratio (58).
99
5.3.1
Data Required Data required by Gas-Sim including solid waste data, landfill characteristics and
climatic data are summarized in Table 5.2.
Table 5.2: Data Required by Land-Gem Model (58) Data Type
Parameter Quantity
Unit
Time Step
Ton
Yearly
-
-
Composition Methane Generation Capacity Methane Generation rate Solid Waste Data
Moisture Content
Soil Data Climatic Data
5.3.2
Year
-
-1
-
Waste Density
3
Ton / m
-
Porosity
vol. / vol.
-
m
-
m / sec
-
Hydraulic Conductivity Characteristics and
m / Ton
%
Leachate Head Landfill
3
2
Landfill Area
m
Soil Layer Thickness
m
-
m / sec
-
mm
Yearly
Hydraulic Conductivity Rainfall
Al-Akaider Landfill gas Generation Land-Gem simulates LFG up to 100 years, 75 years simulation is chosen for
simulation. LFG starts to be generated from the year 1981 to 2055 as a triangular shape, Figure 5.3. The generation is implemented for different confidence intervals; 5% up to 95%.
100
Methane
2,000
1 Year after the closure
1,800
Gas Generated (m3/hr)
1,600
1,400
1,200
1,000
800
600
400
200
0
1985
1990
1995
2000
5% Less Than 90% Less Than
2005
2010
10% Less Than 95% Less Than
2015
2020 Year
2025
25% Less Than
2030
2035
2040
50% Less Than
2045
2050
2055
75% Less Than
Figure 5.3: Land-Gem Methane Generation Result (1981 to 2055)
Using the same approach as Gas-Sim, the most sensitive parameters including methane generation rate and methane generation capacity were obtained from different previous studies and fitted to a probability distribution before being entered to the software. The maximum LFG generation occurred in the year 2021, the year the waste input is discontinued, the same as Gas-Sim. The methane afterward starts to decline but in different approach than Gas-Sim model. Methane generation rate is the almost the same for all different percentiles categories. Figure 5.4 shows the results of the two models as a function of waste quantity.
101
2100 1950 1800
GasSim
LandGem
1650 1500
Methane (m3 / hr)
1350 1200 1050 900 750 600 450 300 150 0 0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
Waste (103 ton)
Figure 5.4: Comparison of the Methane generated using Two Models 5.4 Verification of the Models' Output Since there are no real measurements of methane generated from solid waste degradation at Al-Akaider landfill, model calibration process does not exist. Also, lack of real data will render the output of the simulation processes to a lot of criticism. The objective of this section is to defend the obtained results. This will be performed by comparison with previous studies and with comparing the output of the same site by using different models. Figure 5.4 shows a good match between the results even though the concept behind each model is different (Gas-Sim is a multiphase model while Land-Gem is a single phase model). This is supported by accuracy in the input data as well as using reasonable assumptions by referring to previous studies and site visits to Al-Akaider landfill. Uncertainty was overcome by fitting the parameters to probability distributions before being fed to the models. Also, the Land-Gem model is a sub model within the Gas-Sim environment; therefore, the results are expected to be close together. 102
In 2005, Qdaisat modeled methane generation at Ruseifeh closed landfill, Jordan. Ruseifeh landfill received municipal soil waste as well as industrial solid waste. The proportion of biodegradable organic matter is about 75% while that of the ISW is about 15%. Modeling process was conducted using Gas-Sim and Land-Gem models, the results were verified by real measurements at the site (9). Detailed information concerning solid waste reaching Al-Akaider and Ruseifeh landfills is summarized in Table 5.3. Site specific data for Al-Akaider and Ruseifeh landfills are outlined in Table 5.4. A comparison between the methane generated at AlAkaider and Ruseifeh landfills as a function of waste quantity is presented in Figure 5.5.
Table 5.3: Solid Waste Composition for Different Landfills (5, 9) Property
Jordan Al-Akaider
Ruseifeh
Organic Matter
63 %
52 %
Paper
17 %
23 %
Plastics
11 %
11 %
Glass
2%
2%
Inert
-
-
Metals
2%
2%
Textile
2%
2%
Others
3%
8%
Table 5.4: Site Data for Al-Akaider and Ruseifeh Landfills (5, 9, 40, 42) Property
Al-Akaider
2200 × 103 m2
Biodegradable Matter
80 %
75 %
Non-biodegradable Matter
20 %
25 %
Max. Temperature
25.7 ºC
26.2 ºC
Min. Temperature
8.3 ºC
8.2 ºC
159.8 mm
221.9 mm
Annual Rainfall
103
2
Ruseifeh
806 × 10 m
Area
3
500
450
400
350
CH4 (m3/hr)
300 Ruseifeh Modeled 250
Al-Akaider Ruseifeh Measured
200
150
100
50
0 100
300
500
700
900
1100
1300
1500
1700
1900
Waste Quantity (103 ton)
Figure 5.5: Methane Generated at Al-Akaider & Ruseifeh (Gas-Sim)
It is noted from Figure 5.5 that there is a good match between the methane generated at Al-Akaider and Russiefeh landfills even though there is some difference in the solid waste composition and the climatic data in the two sites. This may be due to the higher non-biodegradable matter content at the Russiefeh than that at Al-Akaider landfill that will adversely affect the biodegradation process. The difference in rainfall quantity will affect the generated gases since it is a function of moisture content. The accuracy of landfill gaseous emissions is usually checked by that of methane as the principal gas among those generated from landfills. From the above discussion; it seems that our estimation is reasonable and therefore the results obtained by using GasSim model are to be utilized in the risk assessment task as shown in the following sections.
104
5.5 Health Risk Analysis This section is concerned with the generated gases and health risk analysis based on the results of the Gas-Sim model. Benzene (C6H6), one of the most important carcinogens will be considered in this discussion. Another non-carcinogen gas will be considered; that is hydrogen sulfide (H2S).
5.5.1
Benzene Surrogate chemicals accounting for 99 % of the carcinogenic total risk were
selected; benzene will be considered in this discussion. The primary routes of benzene absorption are ingestion (from contaminated drinking water) and inhalation (release from contaminated soils, industrial sources and landfills). Benzene is a confirmed group (A) human carcinogen that causes leukemia (the proliferation of white blood cells). Once absorbed, benzene is transformed in the liver first to phenol and then to poly-phenolic metabolites. Benzene has a slope factor of 0.029 (47).
Generated Gases Benzene generated during the solid waste deposition in the landfill is shown in Figure 5.6 as a function of time. The generation rate of benzene in the year 2006 is 13.2 g/hr. It is noted that the maximum generation rate (18.3 g/hr) will be in 2021. This is mainly due to the closure of the landfill in 2020. After 2021, no solid waste will be deposited there and hence the amount of generated gases will decline with time.
105
Benzene 24 22 20 18
Gas Generated (g/hr)
16 14 12 10 8 6 4 2 0
1985
1990
1995
2000
5% Less Than 90% Less Than
2005
2010
2015
10% Less Than 95% Less Than
2020 Year
2025
25% Less Than
2030
2035
2040
50% Less Than
2045
2050
2055
75% Less Than
Figure 5.6: Generated Benzene as a Function of Time Human Exposure to Emissions The exposure model concerns with the human intake of pollutants arising from the landfill. Two scenarios will be presented here; residential with / without plant uptake and workers. The year of interest is 2006. Human exposure is limited to years (0 – 6), the age that is most affected by contaminants. Babies (0 – 1 year), have limited contact to contaminated soils or household dust.
•
Residential with Plant Up-take This section determines the pollutant (benzene) concentration taken up by garden
vegetables growing in vegetation areas near the landfill and estimates the consequent potential intake of the pollutant from ingestion of the vegetables. The 95th percentile intake value at a distance of 1580 m away from the landfill is 8.34 × 10-7 mg/kg/day as shown in
106
Figure 5.7. The chronic daily intake of a 95% confidence is the value at which the sum of the preceding relative frequencies accounts for 95% of the total frequencies. Exposure pathways are shown in Figure 5.8. The risk can be calculated as follows: Risk = Daily Intake Value × Slope Factor Risk = 8.34 × 10-7 × 0.029 = 2.42 × 10-8 Surrogate chemicals / pollutants – including; benzene, chloro-benzene, chloroform, carbon tetrachloride, 1,1 di-chloro ethane, 1,1 di-chloro ethylene, formaldehyde, tetrachloro ethane, toluene and vinyl chloride – that account for 99 % of the total risk were selected and the overall carcinogenic risk was calculated. The total risk is 6.52 × 10-8 which is less than 10-6 and therefore the total risk is acceptable.
Figure 5.7: Exposure Results of Benzene with Plant Uptake
107
Figure 5.8: Exposure Pathways of Benzene with Plant Uptake •
Residential without Plant Up-take The pollutant concentration will be calculated excluding the gases reached the
human body via vegetables. The 95th percentile benzene intake value at a distance of 1580 m away from the landfill is 4.51 × 10-7 mg/kg/day as shown in Figure 5.9. Exposure pathways are shown in Figure 5.10. The risk can be calculated as follows: Risk = Daily Intake Value × Slope Factor Risk = 4.51 × 10-7 × 0.029 = 1.31 × 10-8 Also, surrogate chemicals / pollutants accounting for 99 % of the risk were selected and the total carcinogenic risk was 2.11 × 10-8 which is acceptable.
108
Figure 5.9 Exposure Results of Benzene without Plant Uptake
Figure 5.10 Exposure Pathways of Benzene without Plant Uptake
It is recognized that the risk with plant uptake is greater than without plant uptake. This was expected since the plant ingestion will serve as a new route for benzene other than inhalation.
109
•
Workers Occupational Risk The concentration of contaminant that workers are exposed to is much greater than
residential areas. Workers are exposed to the origin point of emissions. The onsite benzene concentration is 0.000461 mg/m3. Inhalation Risk Calculation: I=
CR × IR × EF × ED BW × AT
I = Daily intake (mg / kg.day) CR = Contaminant Concentration in Air (mg/m3)
[0.000461 mg / m 3 ]
IR = Inhalation Rate(m 3 / day)
[30 m 3 / day for adults]*
EF = Exposure Frequency(hr / day)
[8 working hours / day]
ED = Exposure Duration(years)
[40 years]**
BW = Body Weight (kg)
[70 kg]
AT = Averaging Time(days)
[70 years for carcinogen]
I = 3.8 × 10 −5 (mg / kg.day ) Risk = I × SF = 3.8 × 10 −5 × 0.029 = 1.09 × 10 −6 > 10 −6 *
Un-acceptable
Suggested upper bound value (47) Occupational life time
**
Surrogate carcinogenic chemicals accounting for 99 % of the risk were selected and the total carcinogenic risk was 1.32 × 10-6 which is greater than 10-6. Therefore the overall risk value is unacceptable and workers have to be protected from the emissions of the landfill.
Atmospheric Dispersion This section addresses the impact of the landfill gas on local receptors through atmospheric dispersion. The landfill is assumed as point source and the plume is cone shaped which follows the shape of a Gaussian function, or symmetric bell-shaped distribution.
110
Gas-Sim determines the concentration of a pollutant at a receptor for a user defined species, year, receptor height, direction and distance from the site up to 25 km. The maximum distance for trace gases concentrations is taken to be 10 km. The wind rose for benzene is based on metrological data explained in Chapter Three and is shown in Figure 5.11. The concentration has a maximum value at the center (landfill) and decreases with distance from the landfill reaching a negligible value at Al-Akaider village which is at a distance of 1.58 km.
Al-Akaider Village
Figure 5.11: Wind Rose of Benzene Concentration, 2006
Gas-Sim can also present the concentration of benzene as a graph for a certain year, direction, height and Pasquill category, Figure 5.12. The concentration of benzene for year 2006 at a distance of 1.58 km, height of 1.5 m, south west direction and different Pasquill categories is shown in Table 5.5. The risk values outlined in Table 5.5 are less than 10-6 indicating that the atmospheric dispersion carcinogenic risk is acceptable.
111
Atmospheric Dispersion - Benzene, 95th percentile, 2006, Pasquill A Emissions, 4/23/2006 11:48:37 PM - South West
8.5x10E-6 8.0x10E-6 7.5x10E-6 7.0x10E-6 6.5x10E-6
Concentration (mg/m3)
6.0x10E-6 5.5x10E-6 5.0x10E-6 4.5x10E-6 4.0x10E-6 3.5x10E-6 3.0x10E-6 2.5x10E-6 2.0x10E-6 1.5x10E-6 1.0x10E-6 5.0x10E-7 500
1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000 9500 10000 Distance (m)
Figure 5.12: Benzene Concentration at the South West of the Landfill, 2006 Table 5.5: Benzene Concentration and Risk Values at Different Pasquill Categories Category
*
5.5.2
Concentration (mg/m3) -7
CDI* (mg/kg/day)
Risk Value
-7
3.03 × 10-9
A
2.44 × 10
B
2.41 × 10-7
1.04 × 10-7
3.00 × 10-9
C
1.41 × 10-7
6.06 × 10-8
1.75 × 10-9
D
2.03 × 10-7
8.73 × 10-8
5.52 × 10-9
E
5.20 × 10-7
2.24 × 10-7
6.47 × 10-9
F
2.32 × 10-6
9.97 × 10-7
2.88 × 10-8
1.05 × 10
Chronic Daily Intake
Hydrogen Sulfide H2S is a colorless gas, which is both toxic and flammable. It has a very low odor
threshold, with its smell being easily detected at concentrations well below 1 ppm in air. The odor increases as the gas becomes more concentrated, with the strong rotten egg smell recognizable up to 30 ppm. Above this level, it is reported to have a sickeningly odor up to
112
around 100 ppm. However, at concentrations above 100 ppm, a person's ability to detect the gas is affected by rapid temporary paralysis of the olfactory nerves in the nose, leading to a loss of the sense of smell. This means that the gas can be present at dangerously high concentrations, with no perceivable odor. Prolonged exposure to lower concentrations can also result in similar effects of olfactory fatigue. This unusual property makes it extremely dangerous to rely totally on the sense of smell to warn of the presence of H2S. The only reliable way to determine exposure levels is to measure the amount in the air. The gas is found in varying concentrations in many oil and gas wells and is a by product of many industries including pulp and paper manufacturing, rayon textile production, leather tanning, chemical manufacturing and waste disposal. It is also found in septic tanks, sewers, manure pits, or anywhere bacteria can break down organic matter in an oxygen deficient environment (59).
Generated Gas Surrogate chemicals that account for 99 % of the total non-carcinogenic risk were selected. Hydrogen sulfide as a non-carcinogen gas will be considered in this discussion. Hydrogen sulfide emitted from Al-Akaider landfill site is illustrated in Figure 5.13. It is noted that the maximum generation rate (167.2 g/hr) will be in 2021. The generation rate in 2006 is (126.4 g/hr).
Human Exposure to Emissions Health risk assessment associated with the emission of hydrogen sulfide will be considered here. Two categories will be assessed; residential and workers. Residential risk assessment will be presented by two scenarios; residential with plant uptake and residential without plant uptake.
113
•
Residential with Plant Uptake The 95th percentile intake value at a distance of 1580 m away from the landfill is
1.71 × 10-4 mg/kg/day. The risk (for non-carcinogen) can be calculated as follows: HI =
I , where; RfD
HI = Hazard Index I = Intake (mg / kg. day) RfD = Reference Dose (mg / kg. day) For hydrogen sulfide, the inhalation RfD = 2.57 ×10-4 (mg / kg. day) HI = 0.665 10-6), while residents are exposed to risk of 2.93 × 10-7 which is less than the allowable value
(9)
. This is consistent with the
results obtained here. It is concluded that the calculated health risks are matching together in two of the most important landfills in Jordan; they are Al-Akaider (Northern Jordan) and Ruseifeh (Middle Jordan).
5.6 Environmental Risk Analysis 5.6.1
Vegetation Stress Plants are adversely affected from landfill gases; mainly methane and carbon
dioxide especially when such gases exist in the root zone. Research has shown that vegetation stress can be caused by carbon dioxide at a range from 5 to 10 % (v/v) and methane at about 45 % (v/v). However, methane can be biologically oxidized to carbon dioxide in soil. Therefore, concentration of methane and carbon dioxide can be summed. This summed concentration is then compared to a vegetation stress threshold concentration which is the mid point between 5 and 10 %
(58)
. Concentration of methane and carbon
dioxide at the year 2006 as s function of distance from the landfill is shown in Figure 5.14.
117
It is recognized that plant will be affected if it is within a distance of 157 m from the landfill. Another source of vegetation damage is dust resulting from different practices at Al-Akaider landfill. Dust formed a thin cover on plant leaves and hence inhibiting / preventing the photosynthesis process and therefore the production is sharply affected (40). Vegetation Stress: 2006 110 100 90
% of CH4 and CO2
80 70 60 50 40 30 20 10 0 0
20
40
60
80
5% Less Than 90% Less Than
100
120
10% Less Than 95% Less Than
140 160 Distance (m)
180
25% Less Than Series7
200
220
240
50% Less Than
260
280
300
75% Less Than
Figure 5.14 Vegetation Stress due to CH4 and CO2 5.6.2
Global Impact The global impact module includes global warming potential (GWP) and ozone
depletion potential (ODP). These potentials are determined by summing the emissions of species of interest emitted from the landfill surface. This information can be used to determine the impact of the landfill on the environment. The risk to the global atmosphere from landfill gaseous emissions is determined by estimating the effect of: •
Greenhouse gases
•
Ozone depleting compounds These two classes will be discussed in the following sub-sections
118
5.6.2.1 Global Warming Potential Gas-Sim determines the effect of green house gases and compares the effect of each compound to carbon dioxide. For example; methane has 21 times the effect of carbon dioxide. Table 5.7 shows the species contributing to GWP and their CO2 equivalence.
Table 5.7: GWP Species Emitted from Al-Akaider Landfill (2006, 2006) GWP (tones of CO2)
Species
2005
2006 *
Methane
142000
150000
Carbon Dioxide
22000
23300
1, 1, 1, 2 – Tetrafluorochloroethane
3.63
2.88
1, 1, 1 – Trichlorotrifluoroethane
119
54.3
1 – Chloro – 1, 1 – difluoroethane
125
155
Chlorodifluoromethane
3240
4570
Chloroform
0.216
0.221
Chlorotrifluoromethane
1470
1280
Dichlorodifluoromethane
4250
13600
Dichloromethane
5.57
3.77
Trichlorofluromethane
1710
956
Trichlorotrifluoroethane
336
325
175000
194247
Total *
Projected Values
It is recognized that methane has the highest GWP (average value is 79.23 %) while carbon dioxide contributes to the total global warming potential by 12.3 %. It is recommended to best exploit the emitted methane as a renewable source of energy and hence reducing the environmental problems resulting from its emission to the atmosphere.
5.6.2.2 Ozone Depletion Potential The ozone depletion potential (ODP) is determined in a similar manner to global warming potential but – in this case – with comparing the contributing species to a standard compound namely trichlorofluoromethane (CFCl3). CFCl3 is expected to be emitted due to the presence of small amounts of solvents in the solid waste streams. It may
119
react with the organic carbon presented in solid waste and tri-halo-methanes (THMs) are expected to be released. THMs are considered as very harmful compounds since they are carcinogens. Table 5.8 shows the species contributing to ODP and their CFCl3 equivalence. The highest contribution potential is from dichlorodifluoromethane with an average value of about 54.87 % of the total potential.
Table 5.8: ODP Species Emitted from Al-Akaider Landfill (2005, 2006) ODP (tones of CFCl3)
Species 1, 1, 1, 2 – Tetrafluorochloroethane
2005
2006 *
3.34 × 10-4
1.68 × 10-4
0.0159
7.23 × 10-3
3.54 × 10-4
4.37 × 10-3
0.0939
0.132
1, 1, 1 – Trichlorofluoroethane 1 – Chloro – 1, 1 – difluoroethane Chlorodifluoromethane Chlorofluoromethane
2.09 × 10
Chlorotrifluoromethane
0.105
Dichlorodifluoromethane
0.401
1.52 × 10-3 0.0912 1.28
Dichlorofluromethane
9.41 × 10
-3
7.15 × 10-3
Freon 113
7.88 × 10-3
5.69 × 10-3
Trichlorofluromethane
0.372
0.208
Trichlorotrifluoroethane
0.0447
0.0433
1.06
1.78
Total *
-3
Projected Values
5.7 Public Health Assessment 5.7.1
Employees, Workers and Recyclers Workers involved in solid waste disposal, collection and separation are not
susceptible to the same health risks as other industries or working conditions, in addition; they are at high risk of accidents than average industrial workers are. This vulnerability arises not only from working outdoors, but also because solid waste workers may be exposed to a range of dusty, flammable and even hazardous materials (60). Based upon the site visits to Al-Akaider landfill, it is concluded that the minimum requirements regard the public health are not taken in consideration.
120
•
Engineers’ offices and guard’s room are very close to the industrial wastewater ponds subjecting them to a very sharp bad odor. This is higher than the threshold value and hence they are at high risk
•
Workers and recyclers who used to separate solid waste at the site do not take into account any precautionary concerns, i.e. they do not wear special clothes, gloves and muzzles and their shoes are ragged
•
Compaction and separation processes of municipal solid waste took place simultaneously rendering workers to dust problems in addition to gaseous emissions via inhalation and risk of truck accidents, see Figure 5.15
•
Recyclers who are illiterate used to have their meals near solid waste piles (the surrounding environment is highly polluted as well as their hands)
•
Amount of medicine, cotton, gauze, plasters, sterilizing materials are very limited and inaccessible to all of the employees at the site
Figure 5.15: Workers are at Accident Risk other than Inhalation and Dust
121
5.7.2
Residents of Al-Akaider Village In the previous sections, it was outlined that residents of Al-Akider village are not
at risk either from carcinogenic compounds or non-carcinogenic compounds emitted from the landfill. The public point of view and the newspaper are in contrast with the study output. It is important here to investigate the situation in a transparent scientific manner. Two site visits to Al-Akaider village were conducted during which meeting with people and the family doctor took place. The family doctor as well as people rendered the bad health conditions at the village due to the presence of the landfill. The family doctor summarizes the most common diseases as: arthritis, conjunctivitis, mumps, carbuncle, pox, respiratory diseases and measles (60, 61). The principal complaints from Al-Akaider landfill come from Al-Akaider village (1.58 km from the site). The village residents blame the landfill as the cause of many diseases. A study conducted in 1998 outlined that this assumption was not proved from reviewed medical reports and the disease pattern in Al-Akaider village is the same as in other northern villages. This indicates that the landfill did not cause serious effects or medical problems to residents in the nearby villages (60). A study conducted in 1996 aimed to evaluate the possible adverse health effects that might result from the unsanitary methods of disposing domestic wastes on the residents living in the nearby area of the waste disposal site. To do so, two villages were selected; Al Akaider village and Mansheyyet Al Kuaiber village for control purposes. The control village has almost the same population size, demographic, social, geographical and economic characteristics as Al Akaider village but it is located 30 km away from the landfill (62). The study outlined that Al-Akaider village has higher incidence of asthma and conjunctivitis diseases than the control area. Although there was a marked difference in
122
housefly density between study and control areas, however; this difference was not statistically significant. There was also no statistically significant difference between the study and control areas in terms of parasitic diseases and respiratory diseases (62). Population in the study area are infected by these diseases due to the absence of personal hygienic practices, social practices, lack of cleanliness of houses as well as to the dirty surrounding environment. People also suffer from houseflies, rodents, insects and mosquitoes (60, 61). People at Al-Akaider village live in unsanitary conditions. Some of the toilets are out doors and 50 % of those in doors are dirty and are not well maintained. This means that the families with no toilet facilities defecate in the open air providing suitable site for breeding of houseflies. Solid wastes are collected once a week. The interval between the consecutive collections is enough to provide housefly with sufficient time to complete their life cycle during summer. Most of the families keep animals (chicken, goats, sheep, cows and donkeys) within their living quarters. The animal waste is an attractive environment of houseflies and other insects as well as has a bad and sharp odor. AlAkaider village is located out of the effective flight range of the houseflies and therefore, complain of flies in the village is mainly due to the prevailing unsanitary conditions. The presence of insects, rodents, lice, mosquitoes, cockroaches and fleas is a result of neglecting the basic responsibilities for cleanliness. Although rodents' populations are more mobile, it is not possible, given to the prevailing conditions in the houses described above, to state with confidence that the landfill contributes to the problems of pests as experienced by the people living nearby (39, 60, 61). It was not proved that the environmental and health problems in Al-Akaider village are caused by the unsanitary disposal of solid waste at Al-Akaider landfill. This may be due to the recent improvements introduced in handling and disposing of liquid and solid
123
waste. Moreover; the location and characteristics of Al-Akaider landfill help in minimizing the public health effects of the site (60). It is concluded that the most common health and environmental problems noticed in Al-Akaider village can be due to (60): •
Lack of proper excreta disposal system in some houses
•
Lack of proper refuse and solid waste disposal system
•
Improper control of houseflies
•
Lack of personal hygiene due to lack of sanitary facilities in some houses
5.8 Risk Management Risk assessment alone provides a quantitative value of potential hazardous waste site and waste facilities; however, the risk evaluation is usually carried further through risk management. Risk management is a decision making process that is based on a quantitative value obtained from risk assessment coupled with judgment and experience (47)
. The primary function of risk management is to propose mitigation options that
should minimize the risk associated with the facility on the public health and the environment. This can be achieved by a range of measures including: avoidance of the action, limiting the magnitude of the action, rectifying impacts by rehabilitation or restoration, compensating for the impact by providing substitute resources or environments (28)
. Mitigation options of the risk associated with Al-Akaider landfill to workers and
recyclers are summarized below. Also, some options to be followed to mitigate the continuous complains of Al-Akaider village are outlined.
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5.8.1
Workers Risk Management Workers are at risk since they are exposed to high concentrations of chemicals. The
calculated risk value for carcinogenic compounds is 1.32 × 10-6 while it is 1.23 for noncarcinogenic compounds. Risk can be mitigated by reducing the workers' exposure period to chemicals, this can be achieved by: •
Workers should work 30 hours per week rather than 40 hours
•
Workers should be enforced to use protection covers to avoid direct contact with dust and harmful gaseous emissions
•
Workers are to retire when they reach the age of 50 rather than 60
•
Workers have to visit a specialized doctor periodically, to know the results of examination and to get sick leaves whenever needed
•
Amounts of medicine, cotton, gauze, plasters, sterilizing materials are to be increased and accessible to the employees at the site all the time
The previous options will mitigate the workers' risk to the acceptable levels for both carcinogens (0.743 × 10-6) and non-carcinogens (0.692). Recyclers' are also at risk, moreover; their ignorance, practices and lack of sanitation and public health principles aggravate the problem. It is strongly recommended to segregate recyclable materials of solid waste before disposing them at the landfill. This will eliminate the direct contact of recyclers to dust, gases, accidents, insects and injuries.
5.8.2
Residents Risk Management This study as well as previous studies proved that environmental and health
problems at Al-Akaider village are not caused by the landfill. This is mainly due to the unsanitary living conditions of the village residents. To mitigate the risk and people complains; the following management options should be applied:
125
•
Developing healthy village concept in Al-Akaider village
•
Improving the housing conditions of Al-Akaider village should receive high priority from the government and the responsible authorirites
•
Improving the principles of personal hygiene, public health and sanitation
•
Public health awareness campaigns should be conducted among children especially in primary schools
126
CHAPTER SIX CONCLUSIONS AND RECOMMENDATIONS
Based upon the results of this study conclusions and recommendation can be presented as in the following sections.
6.1 Conclusions 1. Models are useful tools in predicting the leachate discharged and gases emitted from landfills if precise input data are used 2. Landfill leachate as well as the industrial wastewater discharged at the site is a major contributor to the groundwater contamination. The situation is expected to be worse in the near future 3. The increase of nitrate concentration and dissolved solids down stream is an evidence of groundwater contamination at the site 4. The value of risk associated with drinking the water downstream is acceptable for adults while it is not acceptable for children and the risk value is expected to increase in the future due to the continuous migration of contaminants to the groundwater 5. Workers, employees and recyclers at the site are all at risk higher than the acceptable levels from landfill emissions. Other sources of risk are accidents, injuries and dust problems. Therefore immediate actions should be taken to minimize the risk to the acceptable levels and protect their health. 6. The lateral migration model indicated that plants will be affected from the high concentration (greater than 7.5 %) of CO2 and CH4 in the root zone at a distance of 157 m around the landfill
127
7. The global warming potential analysis revealed that Al-Akaider landfill will have a potential of 194,247 tons of CO2 equivalent while the ozone depletion potential analysis revealed that the landfill will have a potential of 1.78 tons of CFCl3 equivalent in the year 2006 8. The risk associated with the current practices of waste disposal at Al-Akaider landfill to Al-Akaider village is minimal 9. The major causes of Al-Akaider village residents' diseases, they are complaining for, are the lack of hygienic principles and their bad living conditions. 10. The landfill is not the major cause of the presence of rodents, flies, mosquitoes and straying dogs at Al-Akaider village
6.2 Recommendations 1. Sanitary landfill sites should be designed as an engineering facility to minimize the adverse effects associated with solid waste disposal. The design must include containment of leachate and gas, daily cover for the working surface, runoff and run on diversions which would result in decreasing the potential of surface and groundwater contamination. Final cover (cap) must be properly designed to minimize the water infiltration into the landfill and the gas emissions into the environment 2. Upstream as well as downstream monitoring wells should be installed within AlAkaider landfill area to regularly monitor the quality of groundwater and to suggest the possible uses of such waters 3. Methane, a renewable source of energy, recovery should be considered as part of any integrated solid waste management plan as an environmentally and economically feasible technology
128
4. Policies should be formulated to encourage integrated solid waste management practices through waste avoidance/reduction, reuse and recycling, and there after final disposal in an environmental sound manner 5. Since workers at Al-Akaider Landfill are exposed to risk exceeding the safe levels; risk management should be implemented as soon as possible to minimize the risk to the acceptable level; this can be achieved by reducing the exposure time and frequency to such emissions 6. Workers are to be examined periodically, under the care of the Ministry of Health, and they have the right to know the results of their examinations 7. Segregation of recyclable materials should be performed before disposing the waste at the landfill to minimize the exposure frequency of recyclers to landfill emissions 8. Al-Akaider village should be developed to the healthy village concept. Housing conditions should receive high priority from the government and responsible authorities 9. Residents of Al-Akaider village must understand and improve the hygienic principles, public health and sanitation to protect their health and the surrounding environment 10. Community participation should be encouraged through education and awareness campaigns. Schools, universities and Non-Governmental Organizations (NGOs) have the right form to conduct such activities 11. The transport of other contaminants such as chloride, calcium, magnesium and heavy metals should be investigated in future studies 12. Establishing a buffer zone around the landfill is to be considered in order to minimize the visual and aesthetic impacts of Al-Akaider landfill
129
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ABOUT THE AUTHOR
Mr. Qrenawi was born in Rafah, Gaza Strip where he completed his primary, preparatory and secondary education. In June 2002, he was granted the Bachelor degree in Civil Engineering from the Islamic University of Gaza (IUG). Thereafter; he worked as a teaching assistant for many courses at IUG for two years. Eng. Qrenawi was the first among the short listed Palestinian candidates for the DAAD scholarship Program (2004 – 2006). He joined the Environmental and Water Resources Engineering at the Jordan University of Science and Technology (JUST) where he obtained his master degree in Environmental Engineering in May, 2006. While pursuing his thesis at JUST, the author worked as both a research assistant and a teaching assistant.
E-mail:
[email protected]
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