ISSN 1063455X, Journal of Water Chemistry and Technology, 2014, Vol. 36, No. 3, pp. 144–151. © Allerton Press, Inc., 2014. Original Russian Text © I.A. Talalaj, 2014, published in Khimiya i Tekhnologiya Vody, 2014, Vol. 36, No. 3, pp. 266–280.
NATURAL WATERS
Adaptation of Water Quality Index (WQI) for Groundwater Quality Assessment Near the Landfill Site I. A. Talalaj Department of Environmental Engineering Systems, Bialystok University of Technology, Wiejska 45A Street, 15351 Bialystok, Poland email:
[email protected] Recieved February 11, 2013
Abstract—In this paper the level of groundwater contamination near the municipal landfill site is exam ined. A modified WQI was used to determine the change in groundwater quality. A total of 127 groundwater samples were analyzed for pH, EC, PAH, TOC, Pb, Cu, Cd, Cr, Zn, Hg. The mean value of the WQI for groundwater outflow from the landfill was 8.01, which means a very high landfill impact. Most contami nated water was in piezometers P2 and P3 located to the east from the landfill border with the WQI value of 9.12 and 10.48, respectively. The WQI in the P1 piezometer, situated to the northwest of the landfill reached a value of 4.41. The highest WQI value in analyzed water was recorded in summer (mean: 10.59); the lowest in March (mean: 4.57). The trend line equation point to a stabilizing water quality in P1 and P2 and a growing trend in P3. DOI: 10.3103/S1063455X14030084 Keywords: water quality index, landfill impact, leachate, pollution.
INTRODUCTION Although the landfills have been identified as a one of a major threats to groundwater resources they are still a common waste management practice in many countries. Areas near landfills have a greater possibility of groundwater contamination because of a potential pollution source of the leachate originating from the nearby site [1–4]. Such a contamination of groundwater resources poses a suitable risk to local resource user and to the natural environment [4]. More recently, regulations in many countries have required the installation of lin ers and leachate collection systems [5]. A highdensity polyethylene geomembrane (HDPE GM) is normally employed in the barrier system for most of municipal landfills. Although a geomembrane is placed at the bot tom of a waste dump, some defects are inevitably introduced into the HDPE during its installation and landfill operation [6]. A result of this is groundwater pollution. To evaluate the groundwater contamination WHO standards for drinking water are usually used [7–9]. But they are not always adequate for potentially strongly contaminated groundwater in the vicinity of a landfill. So, a number of authors have worked out different methods and indices for evaluation of groundwater quality data. They have used: a Water Quality Index (WQI), a multivariante analysis such as cluster analysis and prin cipal component analysis or other statistical and mathematical methods [7, 10–14]. The goal of the current study is assessing the impact of the Hryniewicze landfill site in Poland on the groundwater quality using the WQI. The adopted WQI takes into account the quality of inflow (pollution back ground) and outflow (polluted water) of the groundwater from a landfill. MATERIAL AND METHODS Study Area The Hryniewicze landfill, which is located in the southeastern part of Podlasie Province in Poland (Fig. 1), was chosen for the study. The average rainfall in this region is about 550 mm per year. Approximately 40% of the rainfall occurs in the summer season, 22%—in autumn season, 17 %—in winter, and 21%—in spring. The average annual temperature is about 7°C. The Hryniewicze landfill is one of the biggest landfill sites in Podlasie and has been operated since 1981. The landfill site total area is 40 ha. The total amount of solid waste deposited in the landfill till the end of 2010 was estimated at 308 000 m3. The Hryniewicze landfill consists of five cells (five sections), from which the old 144
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est one—the A section—(closed in 2001) is not equipped with a lining system and is sealed with a 50 cm clay layer to protect groundwater. The leachate generated within other cells was contained by a 2.5 mmthick high density polyethylene liner (PEHD) placed at the bottom. In these cells, leachates are collected by perforated pipes on top of the liner and they are pumped out of site to a retention reservoir. Then, they are subsequently transported outside the Hryniewicze landfill, to a municipal sewage purification plant. The leachate amount is about 25,000 m3 annually.
Fig. 1. The study area (Hryniewicze landfill) with groundwater sampling points.
The analyzed area is covered by a sand formation, which is underlain by a complex of boulderclay. A free groundwater–table lays 0.95 m—5.4 m below the land surface. The landfill is underwashed on the west side by groundwater that flows toward the northeast, southeast, and in eastern directions. Water Quality Index For computing the groundwater quality index we start with the following equation: n
WQI =
∑W S ,
(1)
i i
i=1
where the WQI is the quality index for groundwater impacted by a landfill, Wi is the relative weight for ith pol lutant variable and Si is the sub index score of n is the amount of pollutants. Weights values of the ith of the wi pollutant are calculated for 10 parameters. These parameters were selected basing on their relative importance in municipal landfill leachate composition and their potential of polluting groundwater resources. They include most of variables used for calculation of the Leachate Pollution Index (LPI), proposed by Kumar and Alapat [15] as well as variables used for groundwater monitoring [16]. Calculated relative weight values of each parameter are given in Table 1. w W i = ni , wi
(2)
∑
i=1
where is the weight of the ith pollutant variable and n is the number of groundwater pollutants. The maximum weight of 5 and 4 has been assigned to parameters like Polycyclic Aromatic Hydrocarbons (PAH) and Total Organic Carbon (TOC), which may be good indicators of the groundwater pollution by the leachate. They are strongly connected with landfills and not often found together in other pollution sources. They are typically present in elevated concentrations in landfill leachate and thus often indicate the presence of leachate in groundwater [17]. The electric conductivity (EC) and the pH are given as 1 and 2 respectively, as their high value may also be the result of other sources of pollution, not only a landfill (i.e. domestic efflu ents, fertilizers, rainfall, etc.) and geologic formation [7, 9, 18]. All heavy metals were given the weight of 3, because they do not constitute a frequent groundwater pollution problem at landfills [3]. Most of heavy metals deposited remain inside the landfills, and it has been suggested that < 0.02% is leached out within the first 30 years [19, 20]. In groundwater heavy metals are subject to strong attenuation by sorption and precipitation in plume [3].
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Table 1. Relative weight for parameters. Parameter pH Conductivity PAH TOC Pb Cu Zn Cr Hg Cd
LPI*
Monit.**
wi
Wi
+ – – – + + + + + –
+ + + + + + + + + +
2 1 5 4 3 3 3 3 3 3 Σwi = 30
0.0667 0.0333 0.1667 0.1333 0.1000 0.1000 0.1000 0.1000 0.1000 0.1000 ΣWi = 1
*parameters included in Leachate Pollution Index [15] ** parameters included in landfill monitoring system according to Polish Regulation of Landfill Monitoring [16]
A sub index score (Si) for each parameter is assigned by dividing its concentration (Cp) in each outflow (polluted) water sample by its concentration (Cb) in inflow (background) water sample. Si = Cp/Cb.
(3)
For the pH value the Si should be calculated by placing in the dominator the lower value of pH, because both a decrease and an increase in pH value may indicate a negative impact of landfill: (4) Cp/Cb if cp < cb or Cb/Cp if cp < cb.
(5)
For computing the WQI, the Wi Si product is first determined for each chemical parameter, which is then used to determine the WQI: (6) WiSi = WiCp/Σwi. So, n
∑ (w C i
p
⁄ Cb )
WQI = i=1n . wi
(7)
∑
i=1
When the data for all the groundwater pollutant variables included in WQI were not available, the WQI for groundwater polluted by the landfill have been calculated using the concentration of available groundwater pollutants according to the equation: m
∑ (w C i
p
⁄ Cb )
i=1
WQI = . m wi
(8)
∑
i=1
where m is the number of pollutant parameters in the filtrate. Groundwater Sampling Samples of groundwater were taken since 2004 till 2011. To determine locations of the sampling points, topographic features as well as the direction of the surface and subsurface flows of polluted waters were con JOURNAL OF WATER CHEMISTRY AND TECHNOLOGY
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sidered. Three observation points—P1, P2, P3—were located on the outflow groundwater from the landfill and one observation point—P4—in the inflow waters. In order to obtain as reliable results as possible, sam pling under specific atmospheric conditions, e.g. after periods of intensive precipitation or following long lasting periods without precipitation (droughts), was avoided. The sampling was done four times a year, in 3 month intervals: in March, June, September and December. On the whole, during the research, 127 samples (thirty two from each sampling point) were taken. The samples were analyzed—according to the landfill monitoring guidelines—for pH, EC, PAH, TOC and heavy metals: Cr, Hg, Zn, Pb, Cd, Cu. Regularly collected groundwater samples were transported to the laboratory and stored at 4°C. Determinations were carried out according to the Polish Standards. Determina tion of pH and EC were performed the same day as the samples were collected, using the potentiometric method for pH (according to PN90/C0454001) and the conductometric methods for EC (PNEN 27888:1999). The samples for metal analyses were preserved by addition of HNO3. The heavy metals—except for Hg—were analyzed by optical emission spectrophotometry with inductively coupled plasma (ICPOES) (PNEN ISO 11885:2009), Hg was determined by atomic absorption spectrometry (PBIN 14:25.06.2007). TOC was analyzed with use of infrared spectrometry method (PNEN:1484:1999) and PAH with use of high performance liquid chromatography with fluorescent detection (HPLCFLD) (PNENISO 17993:2005). The data analysis included basic statistics (mean, standard deviation, median, minimum, maximum), lin ear regression of chemical variation vs. time to determine slope and analysis of variance to test for the differ ence of groundwater quality between seasons. The analysis was performed using the StatisticaPL software. RESULTS AND DISCUSSION The statistical summary of the groundwater quality near the Hryniewicze landfill is presented in Table 2. It includes qualitative determinations of ten pollution indicators (Table 2). Table 2. Basic statistics for physicochemical characteristics of inflow and outflow groundwater Parameter pH EC TOC PAH Cd Pb Zn Cu Cr Hg
N 32 32 31 32 32 32 32 32 32 32
Inflow groundwater (background) mean min max std. dev. 6.76 5.7 7.5 0.500 0.515 0.094 1.639 0.443 19.3 0.50 51.1 14.22 3.29 0.00 47.96 9.98 0.006 0.000 0.063 0.014 0.031 0.001 0.094 0.033 0.078 0.000 0.640 0.142 0.018 0.001 0.154 0.035 0.017 0.000 0.116 0.034 0.001 0.001 0.010 0.002
N 95 95 92 95 95 95 95 95 95 95
Outflow groundwater (polluted) mean min max std. dev. 6.96 5.4 7.8 0.475 4.308 0.116 13.25 3.74 112.2 10.9 616.6 122.7 2.78 0.00 96.02 10.82 0.007 0.000 0.070 0.015 0.031 0.001 0.150 0.038 0.176 0.000 8.893 0.964 0.035 0.001 0.850 0.091 0.022 0.000 0.152 0.040 0.001 0.000 0.012 0.002
All in mg/L, expect pH, EC in miliS/cm and PAH in mg/L.
Groundwater flowing into the landfill (background) has a pH value ranged from 5.7 to 7.5, while the pH value of a flowing out groundwater (polluted) sample ranged from 5.4 to 7.8. Polluted water was generally neu tral with a mean pH value of 6.96. pH value of polluted water fluctuates more than the background. Changes in the pH of polluted water indicate on the inflow of leachate into groundwater. The EC value ranged from 94 to 1,639 mS/cm and from 116 to 13,250 mS/cm for background and polluted groundwater respectively. EC showed an increasing trend during flow direction and indicates the impact of the landfill. The TOC concentration is a direct measure of organic compounds in water and it is regarded as a well defined and good parameter determining the contents of an organic substance in water. The TOC value in the studied water amounted on the average to 19.3 mg/L and 112.2 mg/L for the background and contaminated water respectively. The TOC value for the outflow water from under the landfill site indicates their contami nation with an organic substance. The maximum TOC value in the piezometers behind the landfill reached a value of 616.6 mg/L, this clearly indicating strong polluted refluxes flowing into it. JOURNAL OF WATER CHEMISTRY AND TECHNOLOGY
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The value of PAH in background samples ranged from 0.00005 to 47.96 mg/L with mean value of 3.29 mg/L, and from 0.00005 to 96.02 with mean value of 2.78 mg/L in outflow water. The results from both background and water impacted by landfill point to contamination of analyzed groundwater with aromatic hydrocarbons. The presence of these compounds in analyzed water can result from washing away from road surface par ticles of: asphalt rich in aromatic hydrocarbons, car tires (due to vehicle braking) as well as dust from car exhaust gases with high PAH concentration. An additional source of contamination, especially in the flowing out groundwater, can be landfill leachate, what is indicated by high PAH values exceeding 50 mg/L. Heavy metals are the major indicators of anthropogenic impact which having various source like dry ash deposition from incineration plants, industrial effluents, traffic activities, road runoff and landfill leachate. Thus the monitoring of heavy metals contamination may be important to assess the landfill impact on ground water quality [18]. Chemical analysis of polluted groundwater shows the general trend of metal in order of abundance: Zn > Cu > Pb > Cr > Cd > Hg. The similar trend was observed in the case of background water, with only exception of Pb and Cu at second and third places, respectively. The concentration of Cd, Pb and Cr in a polluted groundwater exceeds the WHO standards for the drinking water quality [21]. This could point to the impact of the landfill had it not been for the fact that the metal concentration in the inflow ground water is also exceeded. This means that the inflow water to the landfill is already polluted with cadmium, chromium and lead and sources of heightened concentration shall be looked for outside the landfill. From the presented results it ensues, that both the inflow water to the landfill and the water outflow from this landfill does not meet the WHO standards for drinking water quality [21], because of a high concentration of Cd, Pb, and Cr. Moreover, the study results indicated higher PAH concentration in the water inflow to the landfill (3.29 mg/L) than in the water outflow (2.78 mg/L). That indicates as well, how important it is for the evaluation of the waste landfill impact to compare the quality of the groundwater outflow against that of the inflow. This substantiates also the use of the proposed WQI for water being within the landfill impact area. Therefore, for a further evaluation of the water quality the modified WQI was used. Table 3 presents basic sta tistical WQI data for polluted groundwater. Table 3. Statistical comparison of calculated WQI for groundwater impacted by landfill Piezometer P1 P2 P3
N 32 31 32
Mean 4.42 9.12 10.48
Min 0.52 1.49 0.83
Max 17.30 46.12 98.25
Std. dev. 4.20 11.064 19.848
The highest WQI levels ranged from 0.83 to 98.25, at an average of 10.48, were observed in the P3 piezom eter. High standard deviation value (19.38) is an evidence of strong fluctuations of the water quality in that pie zometer. We may state, that water at that place is strongly polluted with evidently high landfill impact. The average value of WQI in piezometer P2 was also high—9.12, with its minimum at 1.49 and maximum at 46.11. A high average value of the WQI points to a strong impact on the landfill. The most stable water quality was observed in the P1 piezometer; this was indicated by the lowest standard deviation value (4.208). The WQI value for P1 ranged from 0.52 to 17.30 with an average of 4.42, also indicating a visible landfill impact. The Fig. 2 illustrate the WQI value in analyzed piezometers P1, P2 and P3 from 2004 till 2011. A trend line function was superimposed on all the diagrams. The line indicates the slope/direction of WQI changes. Achieved results indicate a decreasing trend of water quality in the P1 and P2 piezometers. Despite the fact, that in December 2010 and 2011 a high WQI value was recorded, the inclination of the trend line indi cates a falling WQI value over the time. In case of the P3 piezometer the situation is somewhat different. We watch here a growing value of the WQI, and the trend line shows an increasing tendency. Two maximum WQI values in June 2007—98.25 and in December 2010—63.00 affect the line slope trend. A high WQI value was affected by a high Zn concentration in June—(8.89 mg/L), and in December 2010—high concentration of PAH (258 mg/L). In 2011 high WQI values result from a high TOC concentration (362 mg/L in September and 369 in December) in examined water. With the use of variance analysis it was tested whether the WQI quality changes over year seasons and in individual piezometers are of any statistical consequence (Fig. 3). Results presented in Fig. 3 indicate that the highest WQI values are recorded in summer (10.59). This is due to the temperature, which intensifies a number of physicochemical transformations occurring in water and intensifies the process of decay. Little lower values were recorded in winter and the lowest in March, when the lowest air temperatures were recorded during the water sampling. According to Table 4 and Fig. 3 it was JOURNAL OF WATER CHEMISTRY AND TECHNOLOGY
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found out that most contaminated water occurs in the P2 and P3 piezometers. However, all the piezometers are under the visibly influence of the landfill. The mean value of WQI in piezometers are 4.42 (P1), 9.12 (P2), and 10.48 (P3). Higher WQI values are accompanied by a greater scatter of results. However, observed changes in the WQI values during seasons of the year as well as recorded differences between individual piezometers are of no statistical consequence. WQI
Sept 2011
March 2011
Sept 2010
March 2010
Sept 2009
March 2009
Sept 2008
March 2008
Sept 2007
March 2007
Sept 2006
March 2006
Sept 2005
March 2005
Sept 2004
y = –0.082x + 5.77
March 2004
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
(a)
Sept 2011
March 2011
Sept 2010
March 2010
Sept 2009
March 2009
Sept 2008
March 2008
Sept 2007
March 2007
Sept 2006
March 2006
Sept 2005
March 2005
Sept 2004
y 0.143 = –x 10.91 +
March 2004
WQI 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
(b)
WQI 4.0 3.5 3.0 2.5 2.0 1.5
y = 0.221x + 6.84
Sept 2011
March 2011
Sept 2010
March 2010
Sept 2009
March 2009
Sept 2008
March 2008
Sept 2007
March 2007
Sept 2006
March 2006
Sept 2005
March 2005
Sept 2004
0.0
March 2004
1.0 0.5
(c) Fig. 2. Distribution of WQI in outflow groundwater from P1, P2 and P3 piezometers during the study period.
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TALALAJ WQI 20
16
12
10.59
8
9.94 6.75
4.57
4 Mean
0
Mean+/ Std. Error
March
June
Mean+/1. 96 *Std . Error
September December
Fig. 3. Results of variance analysis for each season and each piezometer.
CONCLUSIONS Results obtained in this study reveal that the quality of the groundwater near the Hryniewicze landfill has been impacted by the landfill. The EC values, the Zn, Cu, Hg concentration and the TOC in water behind the landfill were higher than in the water inflow to the landfill. The Cd, Pb, and Cr and the pH remained at a sim ilar level. The analysis of the water quality has shown that water flowing into the landfill was already polluted. In the P4 piezometer, adopted as the background, the PAH concentration was higher than in the P1, P2 and P3 piezometers, which were within the landfill impact area. The value of the WQI calculated from gathered data has shown that the piezometers P2 and P3 located at the southeastern side of the landfill were under strongest landfill impact; there the WQI value was found to be respectively 9.12 and 10.48. For the P1 piezom eter the WQI value has reached 4.42. The WQI values distribution over years for individual piezometers indi cates that in the P1 and P2 they stabilize gradually. The line trend slope for these piezometers was respectively a =–0.08 and a = –0.14. The WQI value for P3 has shown an increasing trend and the trend line inclination was a = 0.22. The highest WQI values occurred in summer months (mean value for June–10.59) and this was due to the intensification of physicalchemical processes due to a higher temperature. Obtained results show that using the modified WQI we can assess the landfill impact on groundwater. Moreover, these results provide information undisclosed during a traditional analysis of individual parameters of contamination. The applied WQI can be an important information tool for the landfill policy makers and public about the groundwater pollution threat from landfill. REFERENCES 1. Mor, S., Ravindra, K., Dahiya, R.P., and Chandra A., Environ Monit Assess., 2006, vol. 118, pp. 435–456. 2. Bocanegra, E., Massone, H., Martinez, D., Civit, E., and Farenga, M., Environ Geol., 2000, vol. 40, no. 6, pp. 732– 741. 3. Christensen, T.H., Kjeldsen, P., Bjerg, P.L., Jensen, D.L. Christensen B.J., Baun, A., Albrechtsen, H., and Heron, G., Appl Geochem, 2001, vol. 16, pp. 659–718. 4. Fatta, D., Papadopoulos, A., and Loizidiu, M., Environ Geochem Health, 1999, vol. 21, no. 2, pp. 171–190. 5. Kjeldsen, P., Barlaz, M.A, Rooker, A.P., Baun, A., Ledin A., and Christensen, T., Crit. Rev. Env. Sci. Technol., 2002, vol. 32, no. 4, pp. 297–336. 6. Li, Y., Li, J., Chen, S., and Diao, W., Environ. Pol., 2012, vol. 165, pp. 77–90. 7. Gibrilla, A., Bam, E.K.P., Adomako, D., Ganyaglo, S., Osae, S., Akiti, T.T., Kebede, S., Achoribo, E., Ahialey, E., Ayanu, G., and Agyeman, E.K., Water Quality Exposure and Health, 2011, vol. 3, pp. 63–78. 8. Vasanthavigar, M., Srinivasamoorthy, K., Vijayaragavan, K., Rajiv Ganthi, R., Chidambaram, S., Anandhan, P., Manivannan, R., and Vasudevan S., Environ. Monit. Assess., 2010, vol. 171, pp. 595–609. 9. Longe, E.O. and Balogun M.R., Res. J. App. Sci, Eng. Technol., 2010, vol. 2, no. 1, pp. 39–44. 10. AbuRukach, Y. and AlKofahi, O., J. Arid Environ. 2001, vol. 49, pp. 615–630. 11. Loizidou, M. and Kapetanios, E., Sci. Tot. Environ., 1993, vol. 128, pp. 69–81. JOURNAL OF WATER CHEMISTRY AND TECHNOLOGY
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