closed loop control for odour reduction during the ...

CLOSED LOOP CONTROL FOR ODOUR REDUCTION DURING THE TANNERY BEAMHOUSE LEATHER PROCESSING

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TABLE OF CONTENTS DECLARATION ................................................................................................ DEDICATION .................................................................................................... ACKNOWLEDGEMENT ................................................................................. TABLE OF CONTENTS ................................................................................ II LIST OF TABLES ........................................................................................... V LIST OF FIGURES ........................................................................................ VI LIST OF ABBREVIATIONS ...................................................................... VII ABSTRACT .................................................................................................VIII 1.0 INTRODUCTION ...................................................................................... 1 1.1 BACKGROUND REVIEW ................................................................................ 1 1.1.1 BASIS OF ODOR IN TANNERIES ..................................................................... 1 1.2 PROBLEM STATEMENT ................................................................................. 3 1.3 JUSTIFICATION OF THE PROBLEM ................................................................ 4 1.4 OBJECTIVES .................................................................................................. 5 1.4.1 GENERAL OBJECTIVE .................................................................................. 5 1.4.2 SPECIFIC OBJECTIVES .................................................................................. 5 1.5 IMPORTANCE OF THE STUDY ........................................................................ 5 1.6 HYPOTHESIS ................................................................................................. 5 1.7 SCOPE ........................................................................................................... 6 1.8 LIMITATIONS: ............................................................................................... 6 2.0 LITERATURE REVIEW .......................................................................... 7 2.1 MAJOR SOURCES OF ODOROUS GAS EMISSIONS IN THE TANNERY AND THEIR EFFECTS ..................................................................................................... 7

2.2 ANALYSIS OF ODOR ...................................................................................... 9 2.3 EFFECTS OF ODOR TO THE ENVIRONMENT AND PUBLIC HEALTH ............. 11 2.4 ELIMINATION OF ODOR FROM TANNERY PROCESS LIQUORS .................... 12 2.4.1 METHODS OF REMOVAL OF ODOR WHICH ARE AVAILABLE ................... 12 2.4.2 DEODORATION MECHANISMS FOR VARIOUS GASES IN THE TANNERY. .. 13 2.5 CLOSED LOOP AND OPEN LOOP FEEDBACK CONTROL SYSTEMS ........... 14 2.5.1 ODOR CONTROL WITH CHLORINE DIOXIDE AND HYDROGEN PEROXIDE. ... 15

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2.6 SUMMARY ................................................................................................... 17 3.0 RESEARCH METHODOLOGY ............................................................ 17 3.1 STUDY AREA ............................................................................................... 18 3.2 RESEARCH DESIGN ..................................................................................... 18 3.3 EXPERIMENTAL WORK & DATA COLLECTION PROCEDURES .................. 20 3.4 SAMPLE COLLECTION AND CHARACTERIZATION ...................................... 21 3.4.1 DETERMINATION OF SULFUR AND ORGANIC NITROGEN COMPOUNDS MERCAPTANS) .................................................................................................... 21 3.4.2 GC – MS ANALYSIS OF LIQUID SAMPLES. ................................................ 22 3.5 COLORIMETRIC METHOD FOR H2S GAS ODOR EMISSIONS SAMPLING AND ANALYSIS USING UV/VISIBLE SPECTROSCOPY. .................................... 23 3.5.1 BACKGROUND TO THIS METHODOLOGY .................................................... 23 3.5.2 ANALYSIS OF HYDROGEN SULFIDE GAS BY THE COLORIMETRIC TECHNIQUE .......................................................................................................................... 23 3.5.3 METHYLENE BLUE REACTION: .................................................................. 24 3.6 OPEN PATH UV-VIS SPECTROPHOTOMETRY METHOD OF MEASURING THE CONCENTRATION OF BOTH AMMONIA AND HYDROGEN SULPHIDE IN ODOR SAMPLES OBTAIN FROM TANNERY PROCESS LIQUORS......... 25 3.7 ACTIVE SAMPLING METHODOLOGY FOR H2S GAS EMISSIONS USING THE DRAGER SAMPLING SYSTEM. ................................................................. 26 3.8 COLLECTION OF AMMONIA GAS EMISSIONS USING TEDLAR BAGS ........ 28 3.8.1 SAMPLING PROCEDURE FOR AMMONIA GAS EMISSIONS FROM TANNERY PROCESS LIQUORS ............................................................................................. 28 3.8.2 DETERMINATION OF AMMONIA CONCENTRATION IN AIR SAMPLES USING THE NESSLER’S SPECTROMETRIC METHOD. ...................................................... 29 3.9 DATA PROCESSING AND ANALYSIS ............................................................ 31 4.0

RESEARCH FINDINGS AND DISCUSSION................................... 33

4.2 GC-MS ANALYSIS OF LIQUEFIED GAS SAMPLES (SULFUR AND ORGANIC NITROGEN COMPOUNDS – MERCAPTANS), FROM CLOSED LOOP BEAM HOUSE PROCESSING (LIMING STAGE). .................................................. 35 4.3

RESULTS

FROM THE OPEN

–

LOOP CONTROL SYSTEM

UV-VIS

SPECTROMETRY ANALYZED GAS SAMPLES. ........................................... 35 4.4

RESULTS FROM THE CLOSED-LOOP CONTROL SYSTEM UV-VS SPECTROMETRY ANALYZED GAS SAMPLES. .......................................... 36

4.6 RESULTS OF THE DETERMINATION OF AMMONIA CONCENTRATION IN ODOR SAMPLES USING THE NESSLER’S SPECTROPHOTOMETRIC METHOD IN OPEN LOOP CONTROL SYSTEM OF DELIMING ................. 38 iii

4.7

RESULTS ON THE OPEN PATH UV-VIS SPECTROPHOTOMETRY ANALYSIS OF THE CONCENTRATION OF BOTH AMMONIA AND HYDROGEN SULFIDE GAS IN OPEN-LOOP DELIMING SYSTEM. ............ 39

4.8

RESULTS ON THE OPEN PATH UV-VIS SPECTROPHOTOMETRY ANALYSIS OF THE CONCENTRATION OF BOTH AMMONIA AND

HYDROGEN SULFIDE

GAS IN CLOSED-LOOP-DELIMING SYSTEM. ............................................. 40

4.9

RESULTS

ON THE ANALYSIS OF

HYDROGEN SULPHIDE

GAS SAMPLES

OBTAINED FROM THE TANNERY LIME LIQUORS BY THE CALORIMETRIC TECHNIQUE. ............................................................................................. 40

4.10 DATA

ANALYSIS ON

ODOR

DETECTION THRESHOLD AND INTENSITY OF

THE VARIOUS GAS SAMPLE EMISSIONS FROM TANNERY PROCESS LIQUORS. .................................................................................................. 43

4.10.1 INTRODUCTION ....................................................................................... 43 4.11 STATISTICAL DATA ANALYSIS. ................................................................. 47 4.12 DISCUSSION ........................................................................................... 51 5.0 CONCLUSION AND RECOMMENDATIONS.................................... 55 5.1 CONCLUSION ......................................................................................... 55 5.4 RECOMMENDATIONS.......................................................................... 57 APPENDIX 1: ................................................................................................. 62 APPENDIX 2: ................................................................................................. 64

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LIST OF TABLES TABLE 3.1 STOCK SOLUTION (1000MG/L) .................................................................................. 30 TABLE 4.1 NATURE OF COMPOUNDS IDENTIFIED BY GC – MS IN LIQUEFIED GAS SAMPLES OF MERCAPTANS (OPEN – LOOP CONTROL SYSTEM – LIMING STAGE). ................................... 33 TABLE 4.2 CHARACTERISTICS OF NON-AQUEOUS DISTILLATE GENERATED FROM CONDENSATE LIQUID SAMPLE FROM CLOSED-LOOP CONTROL SYSTEM OF LIMING. ................................. 35 TABLE 4.3 RESULTS FROM THE OPEN-LOOP CONTROL SYSTEM UV - VIS SPECTROMETRY ANALYZED GAS SAMPLES ................................................................................................. 35 TABLE 4.4 RESULTS FROM THE CLOSED LOOP CONTROL SYSTEM UV - VIS SPECTROMETRY ANALYZED GAS SAMPLES. ................................................................................................ 36 TABLE 4.5 DETERMINATION OF ACCURACY ON UV - VIS SPECTROMETRY ANALYZED GAS SAMPLES BOTH OPEN-LOOP AND CLOSED-LOOP CONTROL SYSTEM OF LIMING. ................. 36 TABLE 4.6 DETERMINATION OF PRECISION OF THE RESULTS ON UV - VIS SPECTROMETRY ANALYZED GAS SAMPLES BOTH OPEN-LOOP AND CLOSED-LOOP CONTROL SYSTEM OF LIMING. ............................................................................................................................ 36 TABLE 4.7 STATISTICAL RESULTS OF THE CALIBRATION OF HYDROGEN SULFIDE USING THE COLORIMETRIC METHOD. ................................................................................................. 41 TABLE 4.8 COLORIMETRIC DETERMINATION OF HYDROGEN SULFIDE CONCENTRATION IN SAMPLES OBTAINED FROM BOTH THE OPEN-LOOP AND CLOSED-LOOP CONTROL SYSTEMS OF LIMING. ............................................................................................................................ 41 TABLE 4.9 RESULTS OF ANOVA FOR THE SAMPLES AND ABSORBANCE VALUES (RESPONSES) REPORTED IN TABLE 4.8 ................................................................................................... 42 TABLE 4.10 ODOR THRESHOLD VALUES (PPM) FOR SELECTED ODOROUS COMPOUNDS FROM WASTEWATER TREATMENT PLANTS. ................................................................................ 44 TABLE 4.11 EIGHT-POINT N-BUTANOL ODOR INTENSITY REFERENCE SCALE. ............................. 46

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LIST OF FIGURES FIGURE 3.0.1 MAP INDICATING LOCATION OF SAGANA TANNERIES LTD. (SOURCE; GOOGLE MAPS) ......................................................................................................................................... 18 FIGURE 3.2: TANNING DRUMS ................................................................................................... 19 FIGURE 3.2 MEASURING TANNING CHEMICALS & FEEDING INTO THE DRUMS ........................... 20 FIGURE 3.3: GAS CHROMATOGRAPHY - MASS SPECTROPHOTOMETER (GC - MS), MODEL AGILENT 6890 GC & 5973 MS (SOURCE: CEWAY CHEMICAL SERVICES). .................... 22 FIGURE 3.4 UV - VIS SPECTROPHOTOMETER (MODEL NOVA II) USED IN THE ANALYSIS OF AMMONIA AND HYDROGEN SULFIDE GAS SAMPLES. ........................................................ 31 FIGURE 3.5: (A) GC - MS SPECTRUM OF LIQUEFIED GAS SAMPLES (MERCAPTANS).................... 34 (B) MS SPECTRA AT RT 16.12 (C) MS SPECTRA AT RT 17.89 AND (D) MS SPECTRA AT RT 22.96 ......................................................................................................................................... 34 FIGURE 4.1: UV - VIS SPECTROMETRY ABSORBANCE CURVE FOR THE CONCENTRATION OF AMMONIA GAS SAMPLE IN OPEN-LOOP CONTROL SYSTEM OF DELIMING........................... 38 FIGURE 4.2: UV - VIS SPECTROMETRY ABSORBANCE CURVE FOR THE CONCENTRATION OF AMMONIA GAS SAMPLE IN CLOSED-LOOP CONTROL SYSTEM OF DELIMING...................... 39 FIGURE 4.3: OPEN PATH UV – VIS SPECTROMETRY ABSORBANCE CURVE FOR THE CONCENTRATION OF AMMONIA AND HYDROGEN SULPHIDE GAS SAMPLES IN OPEN LOOP CONTROL SYSTEM OF DELIMING. ...................................................................................... 40

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LIST OF ABBREVIATIONS ANOVA – Analysis of Variance EPA – Environmental Protection Agency GC – MS – Gas Chromatography – Mass Spectrometry H2S – Hydrogen Sulfide HC- Hydrocarbons IR – Infrared MS - Mass spectrometry NH3 – Ammonia Ppb – Parts per billion Ppm – parts per million RT – Retention Time TIC – Total Ion Chromatogram TLV - Threshold Limit Value UV – Ultra Violet VOC’s - Volatile Organic Compounds

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ABSTRACT Toxic odor has for a long time been an inescapable problem facing the leather industry, which has put the industry under serious scrutiny. Eliminating odor from the tannery is a major cause of concern by most environmental protection agencies and various studies have been done towards that goal. In this study, the various causes of odor in the tannery beamhouse were identified with the aim of analyzing and quantifying the various odor-causing factors during tannery beamhouse processing. The study also explores the most cost-effective and environmentally friendly methods of odor elimination in the Tannery beamhouse. Closed-loop control system of beamhouse processing, which includes close monitoring of specific process steps, was adopted, and then its effectiveness was studied and discussed. Through this study it was established that closed-loop control system of beamhouse particularly liming and deliming, reduces intensity and concentration of both hydrogen sulfide and ammonia gas emissions to negligible levels. The research ascertained that the closed loop control system was effective in controlling odor emanating from hydrogen sulfide gas and mercaptans during the tannery unhairing/liming process step, which was evidenced by the zero emission values of such variables obtained from the liming process step. The results obtained from the study also established that the efficiency of closed-loop control system of deliming in terms of ammoniacal odor reduction increased from about 64.3% in open-loop control system of deliming to84.3% in the closed-loop control system. Key Words: Closed-loop control system, Open-loop control system, Odor reduction, beamhouse, GC-MS, UV-Vis spectrophotometer.

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1.0 INTRODUCTION 1.1 Background Review Tanneries all over the world have for a long time been closely associated with bad smell, which is commonly referred to as “odor” and is said to emanate mainly from the tannery effluent and sludge treatment plants, raw hide and skin manipulation and storage as well as during the application of various tanning auxiliaries such as soaking and liming auxiliaries, aldehyde tanning agents and various leather finishing agents (Klemenc and Gantar, 1995; Panda, 2012). Consequently, elimination of odor has been of major concern for several tanneries in the last two decades where chemical oxidation scrubbing, biological scrubbing and biological filtering systems were largely tried (Klemenc and Gantar, 1995). However, these methods have not been entirely successful in eliminating odor in the leather industry, and because of the need of environmental protection and pursuing the goal to make the leather production more “neighbor friendly” there is need for more research to be carried out in this area (Nimmermark, 2004). 1.1.1 Basis of odor in tanneries Leather is known for its particularly high gas emissions, which can sometimes be high enough to cause nuisance and discomfort (EPA, 2000). The substances generating odor are generally low molecular weight and volatile compounds, at least partially soluble in water, with a characteristic functional group as the basis for odor, which is normally categorized as either organic or inorganic (Klemenc and Gantar, 1995).

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The most common gas emissions, which cause odor in tanneries, are ammonia and hydrogen sulfide (Panda, 2012). Hydrogen sulfide is the most frequent odorgenerating compound in the tannery, which is a colorless gas with a typical smell of rotten eggs. Its source can either be organic or inorganic, with the organic sources being mainly the sulfur containing compounds namely; amino acids, Mercaptans and thiourea while the most frequent inorganic sources are sulfates. It is usually produced due to the biological activity of microorganisms under appropriate pH and temperature conditions (Klemenc and Gantar, 1995). It can also be produced during the tannery unhairing/liming process step if the pH is lowered to values below 10 (Covington, 2009). An important parameter for odor impact is the odor concentration. Odor actually reflects the human response to odorants in the air and the base for odor concentration is the human odor threshold, which refers to the lowest detectable concentration. It has been shown that odor contains hundreds of different gases where each gas has its own human odor threshold (Kalman, 200). For instance, the highest permitted odor concentration of hydrogen sulfide gas in workplace ambient air (TLV - threshold limit value) is 7 ppm; whilst ammonia – a colorless gas with a penetrating smell, often arising from biological decomposition of proteins and also the use of ammonium salts in deliming, has a TLV of 50 ppm (Klemenc and Gantar, 1995). Another source of odor in tanneries is volatile organic compounds (VOCs), which are mainly generated as a result of anaerobic decomposition of some sulfur and nitrogen organic substances such as mercaptans, indoles, scatoles and

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amines. Some organic acids, aldehydes and ketones can (which are commonly used in tanneries) also generate unpleasant smell (Klemenc and Gantar, 1995). Since the major source of odor in tanneries is actually due to hydrogen sulfide and ammonia gas emissions from both inside the tannery itself and effluent treatment plant, the proposed study will concentrate on investigating methods that can be incorporated in the tannery beam house section to control such emissions as a primary consideration. 1.2 Problem statement Odor in tanneries has become an inevitable problem making tanneries and the leather production in general to be associated with bad smell, it has made it impossible for tanneries to co-exist and thrive in areas near human settlement and cost effective methods are yet to be introduced to curb the problem. The leather industry in Kenya has for a long time been faced with a lot of challenges that have considerably hindered its growth. The main challenge being in the tanning sub-sector where lack of quality effluent treatment facilities and inadequate technology to control the unpleasant odor emanating from within the leather manufacturing processes, has increased environmental and health costs associated with leather production. Bad odor in the tanning sub-sector is an inevitable problem with most if not all tanneries being associated with bad smell. This perception of tanneries has made it rather difficult for tanneries to be established near settlements without constant complaints from the neighbors. This has put the industry under serious scrutiny by various environmental preservation bodies threatening to close some due to the endless complaints from neighboring communities. For instance Bata Shoe Company is one of the largest tanneries and main shoe manufacturers in Kenya

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and had to close down operations on the beam house section due to the odor that had led to several complaints being raised by the surrounding community members. The proposed study is therefore, aimed at investigating closed-loop control methods that can be incorporated in tannery beam house section for purposes of reducing the bad smell to bearable levels and progressively eliminate it altogether. 1.3 Justification of the problem In the pre-tanning section of leather processing, Hydrogen Sulfide and ammonia gases as well as volatile organic compounds (VOCs) are evolved from process and cause bad odour ([email protected]). From putrefying hides and skins also bad odour comes out. Other sources are from chemical storage in tannery (formaldehyde, methane, etc.) and some organic foul gases from hides and skins during processing (Panda et al., 2012). These emissions from tannery or effluent treatment plant, generally pollute the air, soil, surface water and underground water causing serious health problems because they lie within and around residential areas. Respiratory disorders, diarrhea, dysentery and typhoid are the most serious illnesses among the surrounding communities ([email protected]). Odor in tanneries can be controlled more effectively using the closed loop control methods, which ensure that the smell can be reduced to very bearable levels or even eliminated completely, making it possible for tanneries to exist in an environment without affecting the surrounding communities.

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1.4 Objectives 1.4.1 General objective Alleviation of odor related problems emanating from tannery beam house processing. 1.4.2 Specific objectives 1.

To identify the various causes of odor in the tannery

2.

To analyze and quantify the various odor causing factors during tannery beam house processing.

3.

To explore cost effective and environmentally friendly methods of odor

elimination in the tannery beam house. 1.5 Importance of the study Odor emitted from tanneries is a prominent problem facing the leather industry, with detrimental effects both to human beings and the environment. This study is aimed at mitigating the odorous emissions from the tannery by incorporating the closed loop control system in the tannery during leather processing, in the beam house tannery section which is the main area where odor is emitted. 1.6 Hypothesis Null hypothesis (Ho): Closed-loop control system of beam house processing (viz. liming and deliming) does not reduce odor intensity and concentration of both hydrogen sulfide and ammonia gas emissions to negligible levels. Alternative Hypothesis (H1): Closed-loop control system of beam house processing (viz. liming and deliming) reduces odor intensity and concentration of both hydrogen sulfide and ammonia gas emissions to negligible levels.

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1.7 Scope The study will be covering sources and control of odor in the beam house section of the tannery being the root of odorous emissions in most tanneries. The study will be conducted at Sagana Tannery in Kirinyaga County. 1.8 Limitations: 1. Carrying out the research required a beam house and the college is currently not equipped with a tannery. Forcing me to hire drums and tannery resources and chemicals from Sagana Tannery. 2. Equipment used to analyze the gases is found at Chiromo and required constant travelling. 3. Sample collection bags were hard to find and also very costly. 4. Some chemicals required for the process had to be bought and most of them were very expensive. 5. Financial implications for the project were too high considering that there was no funding for the project.

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2.0 LITERATURE REVIEW This study was carried out with an aim of identifying the factors leading to emission of toxic gases in the tannery beam house section. The study reviews, analyzes and incorporates into this study what others have observed in their studies. This chapter is based on the research questions and addresses the origin and factors that cause toxic odor and its effects to the environment and the tannery industry in general, and what has been done to mitigate these toxic emissions. 2.1 Major sources of odorous gas emissions in the tannery and their effects The major sources of odorous gases in the tannery are low molecular weight and VOCs (volatile organic compounds) evolved during enzymatic action that causes decomposition and oxidation of the hides and skins (Panda et al., 2012). Some of the inorganic gases that are considered foul smelling include Ammonia (NH3) and Hydrogen Sulphide (H2S) evolved during unhairing and deliming stages of tannery beam house leather processing (IUE 8 – updated, 2008). Ammonia can be a nuisance in the environment of the tannery and also an environmental hazard if allowed to accumulate in the ambient air (Battye et al., 1994). Since it is highly soluble in water, once in the atmosphere during chilly weather conditions, it can easily be washed out of the air by precipitation and returned to the earth’s surface (Dinh, 2010). Studies carried out by Holger et al (1998) have also indicated that the gas can also be deposited as dry salt deposits near the emitting source, and being a highly basic compound, it will lead to the formation of salts by reacting with acidic gases in the atmosphere which can subsequently be transported long distances, especially in the absence of clouds.

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Apart from the nuisance ammonia gas emissions cause to both tannery workers and the communities surrounding the tannery due to its strong, sharp and pungent odor, ammonia can also have a negative impact on human health. According to data collected by Dinh (2010); at moderate levels of concentration, ammonia can irritate the eyes and respiratory tract. At high concentrations, it can cause ulceration to the eyes and severe irritation to the respiratory tract. Exposure to even low levels of ammonia can irritate the lungs and eyes. Although various attempts to measure ammonia concentration in livestock production facilities have been made in the past (Groot et al., 1998; Hinz and Linke, 1998; Burns et al., 2003), very little work on ammonia emission rates and control seem to have been done in other commercial entities including tanneries. Hence the need for this study. Hydrogen sulfide is the main compound that causes tannery beam house odor, Hydrogen sulfide (H2S) is a colorless gas that has a characteristic smell of rotten eggs, and it may emanate from organic or inorganic sources. The main inorganic sources are sulphur-containing compounds like mercaptans, thiourea, and amino acids etc. while the organic sources are mostly sulfates. Production of Hydrogen sulfide (H2S) is as a result of biological activities of microorganisms under appropriate conditions of pH and temperature (Klemenc and Gantar, 1995). The odor due to hydrogen sulfide emission is the major source of concern in tanneries, where it is likely to be produced in high concentrations especially if the tannery beam house processing as well as effluent treatment and disposal operations are not properly controlled ((Klemenc and Gantar, 1995). The H2S gas is normally produced in deliming and when alkaline effluent liquors mix with acidic streams. Concentration of 200 ppm Hydrogen sulfide (H2S) for 1

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minute can cause loss of consciousness, 500 ppm causes a deep coma with convulsions and exposure for 1 minute at 900 ppm causes death. The limits for exposure are 10 ppm for 8 hours or 15 ppm for 15 minutes. The odor threshold for H2S is 0.08 – 2 ppm (IUE 8 – updated, 2008). Hydrogen sulfide (H2S) is especially dangerous because at levels over 200 ppm the odor is no longer detectable by the human nose. Portable detection devices are therefore essential. Ammonia on the other hand is a colorless gas with a strong pungent smell commonly produced due to biological decomposition of proteins and when the tannery deliming process step using ammonium salts is not properly controlled; normally a tannery will have VOC – 100ppm, NH3 – 40ppm and H2S – 30ppm (Zahn et al., 2001). As per the Kenyan regulations, the ambient air quality tolerance limits for the work place should not exceed 50μg/m3 for H2S and 100μg/m3 for NH3 (Kenyan subsidiary legislation; 2014). Other malodorous volatile organic compounds are produced due to anaerobic decomposition of sulphur and nitrogen organic substances, indoles, scatoles, amines, and mercaptans. Organic acids and the likes of aldehydes and ketones also generate bad odor (Klemenc and Gantar, 1995). 2.2 Analysis of odor To analyze odor, the focus will not only be on one compound but on the various combinations that alter the effects of odor. Analytical monitoring of individual chemical compounds present in odor samples is usually not practical. As a result, odor sensory methods, instead of instrumental methods are used to measure such odor. Odor sensory methods are available to monitor odor both from source emissions and in the ambient air. However, the sensitivity of the odor sensory method must be significantly greater for measuring ambient odor than for source

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odor emissions due to the fact that the odor in the ambient air is usually much lower in intensity than it is at source (Guidelines on Odor Pollution and Its Control, 2008). Modern methods such as UV spectrometry, gas and liquid chromatography, mass spectrometry IR spectroscopy, determination of TOC, can be used individually or in combination to test for purification efficiency but cannot be used for quantitative analysis of individual odor generating components, and therefore a draeger apparatus that has various indicator tubes can be used for quantitative determination and identification of some odorous compounds as it is easy to use and cost effective. (Brewer et al; 2002) It is possible to quantify and measure odor using standard practices some highlighted by the American society of testing and materials (ASTM E679 and E544) and by the European Union. The best indicator for determining odor is the human sensory response through the nose, which has formed the basis for the olfactometer. The technique used is known as dynamic dilution olfactometry whereby the polluted sample of air is diluted with an odorless sample of air, and the smell of the diluted air evaluated as the concentration of the odor increases gradually. Objective and subjective sensory analysis is applied using a sufficient number of human panelists with the olfactometer. This makes it possible to establish whether there is odor or not. (McGinely et al., 2000). The experiment is repeated until the first perception of odor is experienced. Results of the test are expressed as a concentration, with the units of odor being (OU/m3) which represent the dilution factor up to the odor threshold (minimum detectable amount).

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Further to that, panelists are also able to establish the intensity and the hedonic quality (Brewer et al; 2002). The evaluation of the intensity of odor has seven grades; 0-6 where ‘’0’’ stands for odorless, while ‘6’ stands for extremely strong odor. The other scale used is the Hedonic scale that has nine grades from “pleasant” to “unpleasant”. One of the challenges of the dilution olfactometry is that it will not identify individual odors but the primary advantage is the nose, which is a very sensitive organ, is the actual detector. In cases where instrumental methods are used to analyze odor, the methods rely mainly on the application of gas chromatography (GC), including gas chromatography – mass spectrometry (GC – MS), since this mature separation technology is capable of the efficient separation required for analysis of complex mixtures of odor. In gas chromatography a mixture of volatile substances is injected into a column, which separates the compounds based on their relative vapor pressures and polarities. The compounds are then detected as peaks, which have specific retention times and peak areas being used for qualitative and quantitative determinations, respectively (Guidelines on Odor Pollution and Its Control, 2008). 2.3 Effects of odor to the environment and public health Tannery and effluent treatment plant emissions have highly contributed to air, soil, and water pollution leading to serious health problems since they are situated near residential settlements. Some of the most serious illnesses caused as a result of this pollution include diarrhea, typhoid, dysentery and respiratory disorders ([email protected]). Odor is usually perceived in the brain of humans in response to chemical present in the air we breathe. The characteristic smell produced in the tannery can

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sometimes be high enough to cause nuisance and discomfort to human beings making it difficult for tanneries to thrive near human settlements without constant complaints (Panda et al., 2012). The quality of air is a significant environmental aspect and unpleasant smells produced from mainly industrial activities are an important pollution issue (Yuwono et al., 2004). Recently more attention has been given to odor as an environmental nuisance due to increase in industrialization and more awareness of people requiring a cleaner environment. Therefore, to maintain the quality of the environment more efforts have been made to abate odor problems. (Nimmermark, 2004).

2.4 Elimination of odor from tannery process liquors The emission of odor from the tannery particularly the beam house section can be prevented or abated to acceptable levels through appropriate technological measures. To eliminate odor the methodology to be used is based on the properties of the compounds that lead to production of odor. Elimination of Ammonia (NH3) and Hydrogen Sulphide (H2S) gas emissions can be done through various methods, which include closed loop and open loop feedback control systems, addition of chemical reagents, ozone oxidation, passing of compressed air and biochemical method (Panda et al., 2012). Closed loop control for odor reduction or elimination altogether, in tannery beam house processing will form the basis of this study. 2.4.1 Methods of removal of odor which are available Different methods of removal of hydrogen sulfide and ammonia gas emissions are available and include the following: i.

Addition of chemical reagents; 12

ii.

Passing compressed air;

iii.

Ozone oxidation;

iv.

Passing air in countercurrent to liquor in a packed (activated carbon) bed;

v.

Biochemical and Biological methods.

Out of the above-mentioned methods, passing air in countercurrent to liquor in a packed (activated carbon) bed, is the most economical and industrially feasible (Panda et al., 2012). 2.4.2 Deodoration mechanisms for various gases in the tannery. Different detection and deodoration mechanisms for odor emissions are available (Mauskar, 2008). However, analytical monitoring of individual chemical compounds present in such odor is usually not practical due to the fact that odor emissions often consist of a complex mixture of many odorous compounds. As a result, odor sensory methods, instead of instrumental methods, have been conventionally used quite more often over the years. For known compounds, the odor strength can be reliably estimated by measuring the concentration of the chemical, while for mixtures of unknown substances, sensory method is preferred (Mauskar, 2008). Therefore, three deodoration mechanisms for the respective common odorous gas emissions in the tannery are being recommended for use in the proposed study as follows: I.

Ammonia Type The volatile odorous elements are combined with an organic acid radical to form a non-odorous compound, which is non-volatile. - NH + R – COOH

ii.

R + COONH

Hydrogen Sulfide:

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The Hydrogen Sulfide is converted into a complex organic Sodium salt incorporating Sodium Metabisulfide resulting in a non-volatile, nonodorous and non-poisonous compound. HS + R – COONa iii.

NaS + NaHS

Methyl Mercaptans; The mercaptans are very unpleasant and are commonly produced by rotten proteins (e.g. smells of rotten fish, public urinals) CH SH + R – COONa

CH S Na

The gases are converted to a complex organic salt. Neutrapol is distinguished from other neutralizers by its ability to deodorize not just one type of gas but a wide range of gases, acidic neutral and alkaline, automatically and simultaneously. It can be used in a number of ways: -

Add Neutrapol to recyclable water in scrubber systems; dilute and surface spray

-

Use during thee transportation and / or loading sludges

-

Use during cleaning, continually dip neutrapol into wastewater by using an automatic dripping system or periodically pour into wastewater daily (Panda et al., 2012).

2.5 Closed Loop And Open Loop Feedback Control Systems A control system in which the control action is totally independent of output of the system is known as “open loop” control system whereas control system in which the output has an effect on the input quantity in such a manner that the

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input quantity will adjust itself based on the output generated is called “closed loop” control system. Generally, beam house leather processing in the tannery is normally an open loop control system where there is no close monitoring of the various operations leading to considerable losses in terms of chemicals, time and money as well as reduced efficiency and effectiveness of the entire system (Ziff, 2007). Suggested closed loop control systems for odor control in the tannery beam house are summarized below. 2.5.1 Odor control with Chlorine dioxide and Hydrogen Peroxide. Odor control with Chlorine Dioxide a) Chemistry of odor reduction.

Can react to go to Chlorite or Chloride as follows: i) ClO2 + 1e-

ClO2- (Predominates in neutral/ alkaline

conditions) ii) ClO2 + 5e-

Cl-

+ 4OH- (Predominates in acidic

conditions) b) Odor removal reaction i.

Inorganic Hydrogen Sulfide 5H2SO4 + 8Cl- + 4H2O

5H2S + 8ClO2

PH 5 – 9, Min 2.7ppm of ClO2 oxidises 1.0 ppm of Sulfide. ii.

Organic Reactions are slower and proceed in stepwise fashion. Mercaptans + ClO2

Disulfides

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Disulfides + ClO2

Sulfoxides

Sulfoxides + ClO2

Sulfuric acid

Overall reaction PH 5 – 9, 4.5 ppm of ClO2 oxidises 1 ppm of Mercaptants. Odor control with Hydrogen Peroxide a) Chemistry of odor reduction -

It is supplied as a liquid solution of 50% w/w concentration

-

It is a very strong oxidant with high E0 potential.

-

Easily dosed and controlled into effluent or into air scrubbers.

-

Environmentally friendly by-products i.e. water and oxygen

-

Hydrogen peroxide has no chemical odor of its own, thus overdosing will not cause a chemical odor breakthrough but will only increase the cost.

b) Odor removal reaction i.

Inorganic Hydrogen Sulfide 5H2S + H2O2

acidic PH

S0 + 2H2O

HS- + H2O2

neutral PH

S0 + H2O + OH-

HS- + 4H2O2

neutral PH

S022- + 4H2O + H+

S2- + 4H2O2

neutral PH

SO22- + 4H2O

Acidic conditions consume less peroxide but require larger scrubbing area due to lower solubility of sulfides. It may be advantageous if the gas contains large amount of CO2. Alkaline PH = 10- 11 conditions give fast reaction with removal efficiencies 97 – 99.9%.

16

ii.

Organic Reactions proceed in stepwise fashion. Mercaptans RSH First dissolving RSH + NaOH

RSNa + H2O

Next: Oxidation 2RSNa + H2O2

RSSR

+

2NaOH

(dialkyldisulfide) Reaction is very fast and can occur in the scrubber. RSSR is odorous and must be oxidized further. RSSR + 5H2O2 + 2NaOH

2RSO3Na + 6H2O

The disulfide has very low solubility in water and thus the reaction is slow (Panda et al., 2012).

2.6 Summary The chapter highlights literature written on major sources of odorous gases in the tannery and their effects, methods of elimination of odor from the tannery, and analysis of odor. Also discussed is the closed-loop and open-loop feedback control systems.

3.0 RESEARCH METHODOLOGY

17

3.1 Study Area The study was conducted at Sagana Tanneries Ltd located in Sagana Town, fisheries road. Its geographical coordinates are 0° 40' 0" South, 37° 12' 0" East, and it is found in Kirinyaga county. The Tannery is owned by Mr.Yasin Awale, and focuses on large-scale production of wet blue hides and skins and finished leather both for the local and international

market.

Figure 3.0. Map indicating location of Sagana Tanneries Ltd. (Source; Google maps)

3.2 Research Design The research design applied for this project followed a Quantitative experimental approach. In the first phase of this investigation, the beam house process stages where odor is expected to be emitted in disturbing proportions were identified and then

18

arrangements were made to collect gas sample emissions (using tedlar bags fitted with pitot tubes) for the determination of odor concentration thresholds as well as analyzing the odor components with Gas Chromatography – Mass Spectrometry (GC – MS Model ) at the University of Nairobi’s department of Chemistry. All the reagents used in laboratory work were of analytical grade and tannery chemicals were of commercial grade. Tannery work was conducted at the Sagana tannery where six (6) high quality wet-salted goatskins were sourced from the Dagoretti hides and skins curing premises and processed in sets of three (3); one set following the conventional method while the other one following the closed loop control system of processing. In both cases, the processing was limited to the beam house process steps of soaking, liming, deliming, bating and pickling.

Figure 3.2: Tanning Drums

19

Figure 3. Measuring Tanning Chemicals & Feeding into the drums

3.3 Experimental Work & Data collection Procedures a) Hydrogen Sulphide gas The H2S gas emission samples were collected in duplicate both from the control process experiment and the closed loop control method at three stages of beam house processing (i.e at the final stages of soaking, liming and de-liming) using tedlar bags containing 10ml of methanol solvent. The tedlar bags and contents were then sealed and kept in a laboratory oven set at 30 – 400C for 2hrs. This helped increase the solubility rate of the Hydrogen Sulphide gas in methanol. Thereafter the samples were taken for analysis using GC – MS. (Refrigeration was also done awaiting analysis using GC – MS.) c)

Ammonia gas emissions

The Ammonia gas emission samples were collected in duplicate both from the control process experiment and the closed loop control method at two stages of beam house processing (i.e. at the final stages of soaking, liming and de-liming) using tedlar bags containing 10ml of boric acid.

20

The tedlar bags and contents were then sealed and kept in a laboratory oven set at 30 – 400C for 2hrs. This helped increase the solubility rate of the Hydrogen Sulphide gas in methanol. Thereafter the samples were taken for analysis using GC – MS. (Refrigeration was also done awaiting analysis using GC – MS.) 3.4 Sample collection and characterization The respective gas samples were collected and prepared for analysis as indicated below. Prior to analysis, the gas samples were first trapped in a solution of sodium hydroxide to avoid any loss due to evaporation, or, possible damage to the analyzing equipment, Gas Chromatography-Mass Spectrometry (GC-MS). 3.4.1 Determination of sulfur and organic nitrogen compounds mercaptans) Gas samples were collected during liming and de-liming stages in duplicate (from both open loop and closed loop control systems of beam house processing), to determine the various malodorous sulfur and organic nitrogen compounds (which form the bulk of tannery beam house solid wastes) using 5mm hose pitot tube connected to 3L capacity tedlar bag. The respective gas samples of volume 1 – 5 Ml each were trapped with a solution of sodium hydroxide in the tedlar bags before injecting them into GC – MS for analysis. The sulfur and organic nitrogen compounds in the respective gas samples were identified using gas chromatography (GC-MS) at the University of Nairobi’s department of chemistry (model Entech 7100, USA). This was determined by injecting the respective authentic compounds of concentration 12 ppm with a dilution factor of 5. The retention time (RT value in min) of the various identified 21

compounds are as shown in the results section. The concentration of the compounds in the gaseous sample corresponding to the RT values was calculated as shown below: Concentration in ppm = Sample area x conc. of standard compounds Std. area

3.4.2 GC – MS Analysis of Liquid samples. GC-MS analysis of liquid samples was carried out using GC-MS (Model Entech 7100, USA). The samples were mixed with methanol while shaking and then filtered. The filtered sample was diluted 1:10 then 1 micro drop of diluted sample having less < than 100ppm concentration was injected into the GC-MS. Retention time (RT) versus total ion chromatogram (TIC) presents several peaks. Each peak of distinct RT was analyzed in Mass spectrometry in which the graphs were ploted for m/z ratio i.e. mass charge on abscissa and %

abundance

on

ordinate.

(Akdeniz

et

al.,

2012)

Figure 3.3: Gas Chromatography - Mass Spectrophotometer (GC - MS), Model Agilent 6890 GC & 5973 MS (SOURCE: Ceway Chemical Services).

22

3.5 Colorimetric Method For H2S Gas Odor Emissions Sampling And Analysis Using UV/Visible Spectroscopy. Colorimetric analysis is a method of determining the concentration of a chemical element or chemical compound in a solution with the aid of a color reagent. It is applicable to both organic compounds and inorganic compounds and may be used with or without an enzymatic stage.{Verschueren, 1996 } 3.5.1 Background to this methodology Ultraviolet absorption spectroscopy is often used in process control and emissions measurement applications. Various compounds of interest have strong absorption bands in the UV, including sulfur compounds, oxides of Nitrogen (NOX), aromatic hydrocarbons, ammonia, mercury, ozone, halogens, uranium hexafluoride, metal carbonyls and many other. One of its major advantages over infrared techniques is the lack of interference from carbon dioxide (CO2), saturated hydrocarbons and water vapor, which typically are present at much higher concentrations than the species of interest. [Smith and Webstar, 1989] In certain applications the only UV absorbing specie is the analyte of interest. If this is the case, or its combination of concentration and molar absorptivity is high enough relative to any trace interfering compounds, then any interference free concentration measurement can be made. This approach is the one that was followed in this study. Many sample streams contain multiple species that have overlapping UV absorbance spectra. 3.5.2 Analysis of Hydrogen Sulfide Gas by the Colorimetric Technique Hydrogen Sulfide gas produced in tannery beam house processes is usually a primary, if not the major contributor to the odors associated with such processes (particularly during the tannery unhairing process). The production of this gas is 23

usually accompanied by other organic sulfides and occasionally disulfides in the C1-C6 range (Bethea, 1973). The colorimetric analytical procedure for Hydrogen Sulfide gas (H2S) was carried out as outlined below. 3.5.3 Methylene blue reaction: Method:- The Colorimetric at 670nm after absorption of Hydrogen Sulfide in Cadmium Hydroxide Cd(OH)2 or Zinc Hydroxide Zn(OH)2 solution. The gas samples collected after liming (both in the open loop control system (i.e. conventional beam house processing) and closed loop control system were passed through a 20 ml solution of Cadmium Hydroxide (Cd(OH)2)

for

purposes of dissolving the Hydrogen Sulfide gas (H2S) in the samples prior to injecting them into the colorimeter which was set at 670nm. The Cadmium Hydroxide (Cd(OH)2) also acted as a coloring reagent in this reaction (hence the need for setting the colorimeter at 670nm, which is the most appropriate wavelength for absorbing the methylene blue color developed after absorption of Hydrogen Sulfide gas). TYPE:- Continuous, average value over 10-30 minutes ; procedure takes about 30-45 minutes to reach stable color. Lower detection limit:- 1-3 ppb {National Research Council, 1979} INTERFERENCES;a) Precipitation of Cadmium Hydroxide (Cd (OH) 2 ) from suspension reduced the absorptive capacity and thus cuts recovery and efficiency. [REF 2] b) Nitrogen dioxide (NO2) and Sulfur dioxide (SO2) oxidize absorbed Hydrogen Sulfide (H2S) [Buonicore and Davis, 1992] c) Mercaptans and Sulfides

24

d)

Light sensitive

ELIMINATION OF INTERFERENCES a)

Triethanolamine and citric acid was added to Cd++ solution to prevent

precipitation. b)

Zinc Amine salt was used in the Cd absorbing solution to eliminate

Sulfur dioxide (SO2), Nitrogen dioxide (NO2) effects and make absorbing reagent more stable (Ammonium (NH4) salt of amino sulfuric acid was sometimes used to prevent H2S loss by oxidation). c)

1% STRactan 10 (arabinigalactin) was added to the Cd++ slurry to give

stability in presence of light and during sampling and storage. The methylene blue reaction involved generation of a stable color but required the use of a suspension of Cadmium Hydroxide (Cd (OH) 2 ) and arabinogalactan as an absorbing medium. It was considerably more reliable in manual analysis than the sodium nitroprusside method. The main draw back was interference by sulfides and mercaptans. Use of the methylene blue colorimetric determination following absorption in the STRactan 10 modified alkaline Cadmium Hydroxide (Cd (OH) 2 ) suspension was recommended for the analysis of ambient H2S. 3.6 Open Path UV-VIS Spectrophotometry Method Of Measuring The Concentration Of Both Ammonia And Hydrogen Sulphide In Odor Samples Obtain From Tannery Process Liquors. The spectrophotometer used in this case and the UV light source (emitter) was mounted on a stable platform. Data processing from this measurement was computerized and the results obtained from the absorbance values were as shown in Figure 4.3 in the results section.

25

3.7 Active Sampling Methodology For H2s Gas Emissions Using The Drager Sampling System. Hydrogen sulfide gas is a toxic compound; therefore the dragger sampling system (which is normally used for sampling hazardous substances in the air) was the one used in this study. The gas emission samples were collected both at the start and the end of the liming process step. A suitable medium was used via adsorption or chemisorption. In this case a sodium hydroxide reagent was used as a trapping solution, which is a suitable adsorption reagent for hydrogen sulfide gas. The samples were then colored using 1,5-Diphenylcarbazide and then taken to the department of chemistry university of Nairobi for analysis using UV-VIS spectrophotometry. The data obtained from UV-VIS spectrophotometry was analyzed as shown below: A constant mass (mi) was determined by laboratory analysis and the air volume (v) drawn through the sampling tube. The concentration (ci) of the contaminant was then calculated using the following formula as shown in the result section. ci = mi/V[mg/m3]. The sampling tube featured a primary adsorption layer and a secondary layer, which were analyzed separately in the laboratory. This separate analysis determined whether the entire amount of the measured substance (H2S) was adsorbed. During the sampling process, the measured substance was first adsorbed at the primary adsorption layer. Sometimes the capacity of this layer was not sufficient, as was the case in this study, therefore leading to a breakthrough in the observed readings as a result of

26

additional adsorption at the secondary layer. When this occurred a new sample had to be taken because it was not possible to be certain of whether, the entire amount was adsorbed by the two layers (i.e. the secondary layer could also have experienced breakthrough). Since the air volume drawn through the sampling tube is a function of the measured substance Hydrogen Sulfide (H2S) and the expected concentration, the volume of the air sample was in the range of 20-50ml. This air volume was used as a reference for the concentration calculation (following the laboratory analysis) and hence the pump and to meet strict criteria. The dragger sampling system used in this study consisted of a dragger tube pump (accuro), which is normally used for short-term measurements. A silica gel tube Type B was used in this case. Its primary adsorption layer has a capacity of 480mg, and a backup adsorption layer 1,100mg. The concentrations obtained from the UV-VIS Spectrophotometer were usually given as a content of the samples being measured in a reference substance. For the measurement of the actual hydrogen sulfide gas in the sample the observations were subjected into an appropriate engineering unit so as to give the sample, simple and handy figures for indicating the concentration. High concentrations are generally given in volume percent (vol -%) i.e. 1 part of a substance in 100 parts of air. For example if air consists of 21 vol -% oxygen, it means that 100parts of air contain 21 parts of oxygen. In smaller concentrations the engineering unit ppm (ml/m3) is used. The concentration ppm means 1 part of a substance in 1 million parts of air. Since each volume is related to a corresponding mass, the volume concentrations of gaseous substances can be converted into mass per unit volume and vice versa.

27

These conversions must be done at a specified temperature and pressure since the gas density is a function of temperature and pressure [National Research council, 1979]. For measurements at work places, the reference parameters are 200C AND 1013hPa. Conversion from mg/m3 to ppm = [ppm] = mole volume/molar mass. Concentration

The mole volume of any gas is 24.1 l/mole at 200C and 1013hPa, the molar mass (molecular weight) is gas specific. 3.8 Collection Of Ammonia Gas Emissions Using Tedlar Bags Odor bags were filled using a depression pump that works on the basis of the “lung” technique. The bag was placed inside a rigid container evacuated using a vacuum pump. [Jeon and Hwan-Sa, 2009]. This method avoids contamination because there is no direct contact between the pump and the sample. In order to get representative and reproducible results, it is necessary to adapt the sampling technique to the types of odor sources. In general when a gas sample is very concentrated and it is very hot and humid and necessary to use a dilution device for avoiding condensation risks. 3.8.1 Sampling Procedure For Ammonia Gas Emissions From Tannery Process Liquors A known volume of gas sample (15ml) obtained from the process liquors (liming and deliming stage) in duplicate, was pumped into tedlar bags through a narrow plastic tube, which contained a trapping liquid. In this study, boric acid was used. The samples were refrigerated awaiting analysis in the department of chemistry, using the Nesslers method. 28

This was done for both the open-loop and closed-loop processes. 3.8.2 Determination Of Ammonia Concentration In Air Samples Using The Nessler’s Spectrometric Method. The gas samples collected during liming and deliming were passed through a trapping solution (boric acid), this is to convert them to liquid form, as Nessler’s method does not determine the concentration of gaseous samples. The measurement of ammonia concentration in aqueous samples by the Nessler’s method depends on that the graduated yellow to brown color produced by the Nessler-Ammonia reaction is strongly absorbed by a wide range: (λ= 400-500nm)

Reagents used: 1. Ammonia free water about 2Litres by simple distillation (boil the water) 2. Standard NH3-N solution (1000ppm). Weight 3.819g of anhydrous NH4Cl, dilute in 1000ml. ammonia free water. *Anhydrous NH4Cl, dry in oven 1000C for an hour. 3. K-Na Tartarate: (Rochelle salt solution). -

50g KNa-Tartarate in 100ml H2O (free ammonia) you can boil this solution to expel ammonia

4. Nessler reagent: A – (100g Hg I2 + 70g KI) Dilute in small quantity of NH4+ true water (about 50ml) B – (160G NaOH dilute to 50ml (NH4+ free) water. Add (A) to (B) stir gently, dilute the final volume to 1Litre, stored in borosilicate bottle and out of sunlight – it will stay about 1 year.

29

PROCEDURE: 1. Preparation of the standards was done as shown below Stock solution – 5ml/100ml distilled water (50mg/l) Table 3. Stock solution (1000mg/l)

From 50mg/l

5ml/ 50ml distilled water 5mg/l 4ml/ 50ml distilled water 4mg/l 3ml/ 50ml distilled water 3mg/l 2ml/ 50ml distilled water 2mg/l 1ml/ 50ml distilled water 1mg/l

2. 50ml of each standard was taken 50ml of distilled water (free ammonia as blank) 50ml of sample Sewage water was diluted 1:10 N 1: 20 3. 1ml of KNa tartarate (filter before use) was added. 4. 1ml of Nesslers reagent, was added, then left for 5 minutes. 5. The solution was colored and read at fixed wavelength (425 nm). -

A straight curve was plotted

-

Result was reported

30

Figure 3.4 UV - VIS Spectrophotometer (Model nova II) used in the analysis of Ammonia and Hydrogen Sulfide gas samples.

3.9 Data Processing and Analysis 1. CONCENTRATIONS Average odor and chemical concentrations for the various gas samples were calculated from GC-MS measurements by using the appropriate conversion factor for calculating ppm to mg/l or percentages 2. STATISTICAL ANALYSIS Statistical regression analysis was used to analyze total (H2S + NH3 + VOCs) and individual (H2S + NH3 + VOCs) gas concentrations and emission rates. Total and individual analysis was performed with and without VOC data. The justification for the analysis without VOC data was to test whether H2S & NH3 could be used to predict odor when VOC data are unavailable. The reason that VOC data may not be available is

31

that VOC measurement is more expensive, time-consuming and advanced than H2S and NH3 measurement which can be conducted with a variety of commercially available and portable gas analyzers (Akdeniz et al; 2012).

32

4.0 RESEARCH FINDINGS AND DISCUSSION 4.1 GC-MS Analysis Of Liquefied Gas Samples (Sulfur And Organic Nitrogen Compounds – Mercaptans), From Conventional Beam house Processing (Liming stage). GC-MS analysis of the liquefied gas samples collected from the conventional beam house processing (liming stage) was carried out to confirm the nature of compounds present, as shown in the table below. Table 4. Nature of compounds identified by GC – MS in liquefied gas samples of mercaptans (Open – loop control system – Liming stage).

RT

Base

m/z

of Predicted

Nature of

From

peak

molecular ion compound from the

GC

from MS

peak

hit list

compound

3.52

92

135

Pynole-2-

Amide

carboxamade 3.72

93

121

Phenol

Alcohol

13.99

70

217

Uric acid

Carboxylic acid

15.63

70

223

Substituted

Pyrazine

Pyrazine 16.12

17.89

73

69

255

280

n-Heptadecanoic

Carboxylic

acid

acid

Oleic acid

Carboxylic acid

22.96

58

297

Dasycarpida-1methanol acetate

33

Ester

MS spectra of the liquid samples recorded at RT values 16.12, 17.89 and 22.96 is shown in Fig. 1b, 1c and 1d.

Figure 3.5: (a) GC - MS Spectrum of liquefied gas samples (mercaptans) (b) MS spectra at RT 16.12 (c) MS spectra at RT 17.89 and (d) MS spectra at RT 22.96

34

4.2 GC-MS Analysis Of Liquefied Gas Samples (Sulfur And Organic Nitrogen Compounds – Mercaptans), From Closed Loop Beam House Processing (Liming Stage). Table 4. Characteristics of non-aqueous distillate generated from condensate liquid sample from closed-loop control system of liming.

Parameters

Unit

Values

Pour point, 0C

0

< -27

Hydrogen Sulfide

ppm

Not detected

Merceptant

ppm

Not detected

Total sulfur

% by wt.

0.94

Water content

% by wt.

4.8%

Density at 200C

g/cc

0.8895

Molecular wt.

-

284.6

Kinematic viscosity at 400C

cSt

217z

Gross calorific value

kJ/Kg

32956

C

sulfur

4.3 Results from the open – loop control system UV-VIS Spectrometry analyzed gas samples. Table 4. Results from the open-loop control system UV - VIS Spectrometry analyzed gas samples

Liming

Deliming

The M&L for NH3 was 98ppm

The M&L for NH3 was 112ppm

The M&L for H2S was 262ppm

The M&L for H2S was 88ppm

35

4.4 Results From The Closed-Loop Control System UV-VS Spectrometry Analyzed Gas Samples. Table 4. Results from the closed loop control system UV - VIS Spectrometry Analyzed gas samples.

Liming

Deliming

The M&L for NH3 was not detected

The M&L for NH3 was not detected

The M&L for H2S was not detected

The M&L for H2S was not detected

The detection limits for both ammonia and hydrogen sulfide gas samples were calculated using the following procedure: 1) Generation of 16 sequential spectra using UVS 2) Creation of 15 absorption spectra using the back to back spectra. 3) Quantification of the target analytes using the standard PLS matrix for ammonia and Hydrogen Sulfide. 4) Calculation of the standard deviation of the 15 quantifications (replicates) in each case. 5) Calculation of the MDL by multiplying the standard deviation by three.

Table 4. Determination of accuracy on UV - VIS Spectrometry analyzed gas samples both open-loop and closed-loop control system of liming.

Gas

Reference

n

Ppm

Mean

Accuracy

Ppm

%

NH3

31

15

31.77

1.7

H2S

75

15

77.60

2.6

Table 4. Determination of Precision of the results on UV - VIS Spectrometry analyzed gas samples both open-loop and closed-loop control system of Liming.

Gas

n

Mean

St. Deviation Precision

36

Ppm

Ppm

%

NH3

15

31.77

1.34

4.23

H2S

75

77.60

2.64

3.39

4.5 Results of the determination of Ammonia concentration in odor samples using the Nessler’s spectrophotometric method in open loop control system of deliming

37

Sample solution Blank Solution Figure 4.1: UV - VIS Spectrometry Absorbance curve for the concentration of Ammonia gas sample in open-loop control system of deliming.

4.6 Results Of The Determination Of Ammonia Concentration In Odor Samples Using The Nessler’s Spectrophotometric Method In Open Loop Control System Of Deliming

38

Sample solution Blank Solution

Figure 4.2: UV - VIS Spectrometry Absorbance Curve for the concentration of Ammonia gas sample in Closed-Loop control system of deliming.

4.7 Results On The Open Path UV-VIS Spectrophotometry Analysis Of The Concentration Of Both Ammonia And Hydrogen Sulfide Gas In OpenLoop Deliming System. Ammonia gas was characterized by multiple sharp peaks with relatively small absorbency between peaks, usually known as “fine structure”, while hydrogen Sulphide was characterized by broad absorbance band (peak absorbance at 196nm with secondary peaks at 192 and 200nm) that showed no fine feature structure hence referred to as a broad absorber (Figure 3).

39

Figure 4.3: Open Path UV – VIS Spectrometry Absorbance curve for the concentration of ammonia and Hydrogen Sulphide gas samples in open loop control system of deliming.

4.8 Results on the open path UV-VIS Spectrophotometry analysis of the concentration of both ammonia and Hydrogen Sulfide gas in closedloop-deliming system. The open path UV-VIS Spectrophotometry analysis of odor samples obtained from the closed loop control system of deliming showed no significant absorbance values at 192 – 200nm. The closed loop control system of deliming was effective in controlling the emission of these gases, therefore my method was effective. 4.9 Results on the analysis of Hydrogen Sulphide gas samples obtained from the tannery lime liquors by the calorimetric technique. The results obtained for the lower detection limits of hydrogen Sulphide gas concentration in the open loop control system of liming at 670nm was in the

40

range of 0.24-34ppm, whereas the lower detection limit in the closed loop control system of liming was in the range of 15 – 1500mg/l (0.015 – 1.5ppb). Table 4. Statistical results of the calibration of Hydrogen Sulfide using the Colorimetric method.

Parameters

Characteristic

Wavelength (nm)

670nm

Molar absorptivity (L mol-1 cm-1)

1.4 x 103

Linear range (mg/l)

0.5 – 20.00

Number of Samples

5 X 2 = 10

Intercept of calibration curve

0.0114

Slope of calibration curve

0.0456

Correlation coefficient

0.997

F Statistic of the model

1642.68

Limit of detection (mg/l)a

0.16

Table 4. Colorimetric determination of Hydrogen Sulfide concentration in samples obtained from both the open-loop and closed-loop control systems of Liming.

Sample No.

H2S

concentration H2S

concentration Absorbance values

(mol/l) in closed- (mol/l) in open-loop at 670nm loop control system control system of of liming.

liming.

1

0.00030

0.50050

0.579

2

0.00010

1.00000

0.327

3

0.00050

0.00100

0.682

4

0.00050

1.00000

0.604

5

0.00030

0.50050

0.468

6

0.00030

0.50050

0.357

41

7

0.00030

0.50050

0.421

8

0.00030

0.50050

0.480

9

0.00006

1.09990

0.469

10

0.00030

0.50050

0.564

Mean = 0.000296

Mean =0.6103

Mean = 0.4387

Sd = 0.00000088

Sd= 3.162

Sd = 0.8138

Table 4. Results of ANOVA for the samples and absorbance values (responses) reported in Table 4.8

Term Constant x1 X2 x1 x1 X2 x2 x1 x2 Regression R a Probability bF

Pa 0.000 0.004 0.210 0.127 0.556 0.096 0.025

Coefficient 0.494 0.167 0.056 -0.086 - 0.031 - 0.101

Fb 17.11 1.91 2.99 0.38 3.69 5.25

0.888 Value

statistics

Response = bo + b1 + b1 x1+ b2 x2 + b11x1 x1 + b22x2 x2 + b12x1 x2 Where bo is the average of the results of the replicated center point. The coefficients b1 and b2 are the main half-effects of the variables x1 and x2,, respectively, b11 and b22 are the squared effects, and b12 is the two-factor interaction effect. 4.10

Data analysis on Odor detection threshold and intensity of the

various gas sample emissions from tannery process liquors. 4.10.1 Introduction An odor detection threshold relates to the minimum odorant concentration required to perceive the existence of the stimulus, whereas an odor recognition 42

threshold relates to the minimum odorant concentration required to identify the stimulus. The detection threshold occurs at a lower concentration than the recognition threshold. Odor concentration is measured as dilution ratios and reported as Dilution Threshold and Recognition Threshold or Dilution to Threshold (D/T) and sometimes assign the pseudo-dimension of odor units per cubic meter. Dilution to Threshold (D/T) ratio is a measure of the number of dilutions needed to make the odorous air non-detectable. Odor unit is the concentration divided by the threshold. Odor Intensity: Odor intensity is the strength of the perceived odor sensation. Perceived odor intensity is the relative strength of the odor above the recognition threshold. It is related to the odorant concentration. Generally odor intensity increases with the odorant concentration. The relationship between intensity and concentration, can be expressed as: I = k (C)n Or Log I = Log K + n Log (C) 13 Where; I - Intensity; C - concentration; k - constant and n - exponent, This is known as Stevens’ law or the power law. For odors, n ranges from about 0.2 to 0.8, depending on the odorant. For an odorant n equal to 0.2, a tenfold reduction in concentration decreases the perceived intensity by

43

a factor of only 1.6, whereas for an odorant with n equal to 0.8, a tenfold reduction in concentration lowers the perceived intensity by a factor of 6.3. This is an important concept that is related to the basic problem of reducing the odor intensity of a substance by air dilution or other means. Odor Intensity is expressed in parts per million of butanol. The odor intensity is usually stated according to a predetermined rating system. Widely used scale for odor intensity is the following: 1 - Barely perceptible 2 - Slight 3 - Moderate 4 - Strong 5 - Very strong (Half score is used when the observer is undecided) Table 4. Odor Threshold values (ppm) for selected odorous compounds from wastewater treatment Plants.

COMPOUND

ODOR

CHARACTERISTIC

THRESHOLD

ODOR

(ppm) Hydrogen

Sulfide 0.0005

Rotten eggs

(H2S) Methyl Mercaptans 0.0016

Decayed cabbage

(CH3SH)

Dimethyl

0.001

Decayed Vegetables

Sulfide(CH3)2S)

44

Ammonia (NH3)

5.2

Pungent irritating

Triethylamine

0.0004

Ammonical, Fishy

Dimethyl Disulfide 0.003

Vegetable Sulfide

(CH3)2S2) (Source: ChanJeon et al, 2009) Odor intensity due to Hydrogen sulfide and ammonia gas emissions in both the open loop and closed-loop control systems of liming and deliming was calculated using the formula; I = k(C)n Where I is the odor intensity, C is the mass concentration of odorants in ppm, and k and n are constants that are different for every odorant (McGinley and McGinley, 2000). However for purposes of this study, k and n were taken as 0.82 and 0.8, respectively, for both Hydrogen sulfide and ammonia gas emissions. It should be noted that these two constants are valid only for the 8-point n-butanol intensity scale defined in Table 11. I = k(C)n n ranges from 0.2 to 0.8, depending on the odorant. (For strong odorants such as hydrogen sulfide and ammonia, n = 0.8). Table 4. Eight-point n-butanol odor intensity reference scale.

0

0

No odor

1

120

Not annoying

2

240

A little annoying

3

480

A little Annoying

4

960

Annoying

45

5

1940

Annoying

6

3880

Very Annoying

7

7750

Very Annoying

8

15500

Extremely Annoying

(Source: Zhang et al; 2002) For instance; results from the open-loop control system UV-VIS Spectrometry analyzed samples gave the mean concentration of Hydrogen sulfide as 262 ppm for liming and 88ppm for deliming. The odor intensity due to Hydrogen sulfide gas emissions in conventional liming was calculated as follows: I = k(C)n = 0.82 x 262 x 0.8 = 171.87 = 172 ppm. (This odor was a little annoying). Similarly, the odor intensity due to hydrogen sulfide gas in emissions in closedloop control system of liming was calculated as follows: I = 0.82 x 88 x 0.8 = 57.728 = 58ppm (this is not annoying, as shown in Table 4.11). Likewise, results from the open-loop control system UV-VIS Spectrometry analyzed samples gave the mean concentration of ammonia as 98ppm for liming and 112 ppm for deliming. The odor intensity due to ammonia gas emissions in conventional liming was calculated as follows: I = k(C)n = 0.82 x 98 x 0.8 = 64.288 = 64ppm (not annoying according to table 4.11).

46

Using the same formula, the odor intensity due to ammonia gas emissions in conventional (open-loop control system) deliming was calculated as follows: I = k(C)n I = 0.82 x 112 x 0.8 = 73.472 = 73.5 = 75ppm (not annoying) according to table 4.11 Also, odor intensity due to Hydrogen sulfide gas emissions in conventional deliming was calculated as follows I = 0.82 x 88 0.8 = 57.728 = 58ppm (no odor according to table 4.11). Odor intensity due to either hydrogen sulfide or ammonia gas in closed loop control system of deliming was zero as the UV-VIS spectrophotometer did not detect any of the two gases in the respective samples. Thus no odor was produced in the closed loop control system of deliming, as there were nil emissions. 4.11 Statistical data analysis. For each sample, five replicates were measured and mean of the predicted concentrations was reported. Based on these replicates, standard deviation was calculated and divided by mean of results to yield percentage relative standard deviation (RSD%) after multiplication by 100. Percentage relative error was obtained by dividing the differences between the predicted concentrations multiplied by 100. Percentage recovery was obtained by dividing the predicted concentration values by the actual amount (calculated) multiplied by 100. (Shariati, 2008) In order to examine the applicability of the various recommended methods for the determination of both hydrogen Sulphide and ammonia, the absorbance of a

47

series of solutions (prepared from the respective samples for both open-loop and closed loop control systems of liming and deliming) containing varying concentrations of H2S and NH3 in the optimal conditions was recorded against the corresponding reagent blank at the appropriate wavelength UV-VIS Spectrophotometry as indicated in the materials and methods section. The univariate calibration curve (in the case of open loop control system of liming colorimetric determination of H2S) was linear in the range of 0.5020.00mg/l. the statistical parameters of the constructed calibration curve are summarized in Table 4.7. No H2S was detected in samples obtained from the closed-loop control system by liming; hence no calibration curve was constructed from the absorbance values for closed-loop control system of liming. As data in table 4 shows, the linear range of colorimetric method for the determination of hydrogen sulfide is relatively wide. Analysis of variance (ANOVA) of the colorimetric determination of H2S in samples obtained from both the open loop and closed-loop systems of liming (Table 8) is given in table 9. It was found that the regression between the absorbance values (response) and factors (model/ experiment) was reliable due to the high correlation coefficient (R=0.888) and very low P value (0.025) of the regression. This P value indicated that the variation was mainly (about 88.8%) due to the variation in the factor levels. Among the linear terms the concentration of Hydrogen Sulfide (H2S) in samples obtained from the open loop control system of liming was found to be highly significant as is reflected in the very low calculated P value (0.004) and high statistics. The data on odor detection threshold and intensity generated from the analysis of samples obtained from both open-loop and closed loop control systems of

48

beam house processing (viz. liming and deliming process steps) was compared using the F Distribution test according to Brykit, (1985). This was meant to test the hypothesis that closed-loop control system of beam house processing reduces odor intensity and concentration of both H2S and ammonia gas emissions to negligible levels. The significance of the difference in the open loop and closed loop standard deviations was evaluated by calculating the Fratio statistic as, F = S20 S2c

F= (0.7486)2 (0.0163)2

F = 0.5604 0.0003 F = 1868

Where S0 and Sc are the standard deviations of the open loop and closed loop UV – VIS Spectrometry analyzed odor samples, respectively. The calculated Fratio (as shown above) was not within the limits for a 95% confidence level at 5 degrees of freedom (i.e. 0.139 to 7.146). Therefore, the standard deviations of the open loop and closed loop control systems were significantly different. So it was not necessary to pull them together. The relative standard deviation (RSD) was calculated using the formula: RSD = s Sm 49

Where; s = standard deviation of open loop control system of liming Sm

= mean of open loop analyzed samples (mean of closed-loop

analyzed samples if s is for closed loop analyzed samples). From the results obtained in this study the relative standard deviation for closed-loop; RSD = 0.0000008 0.000296

RSD = 0.00296

From the results obtained in this study the relative standard deviation for open loop; RSD = 1.92994 0.6103

RSD = 3.162 The RSD for the closed loop was found to be less than 50% meaning that both the data and the method were acceptable.

50

4.12 DISCUSSION Major sources of odor in tanneries are due to hydrogen sulfide and other organic sulfur compounds such as mercaptans as well as ammonia gas emissions. Prior to this research work there has been no effective technology of eliminating or reducing this odor menace in tanneries particularly beam house processing. Results obtained from GC-MS analysis of the liquefied gas samples collected from the conventional beam house process indicated that the nature of the odorous causing compounds during liming include amides, alcohols and carboxylic acids among others (Table 1), which has base peaks from the Mass spectrometer of 92, 93 and 70 respectively.

51

From the literature, individual analysis and monitoring of individual chemical compounds present in odor samples is usually not practical (Guidelines on Odor Pollution and its Control, 2008). In the present study, to make the analysis of odor more effective and practical the samples meant for analysis were liquefied prior to analysis with GC-MS. Analysis of samples obtained from the closed-loop control system by liming indicated zero values for both Hydrogen Sulfide and mercaptans, which meant that this method was very effective in controlling the emission of Hydrogen sulfide gas as well as other organic sulfur compounds such as mercaptans during liming (Table 4.2). This was confirmed by the extremely low values of the percentage weight of total sulfur and water content of the GC-MS analyzed samples. Modern methods of odor analysis have their own limitations, as they are not effective in quantifying the odor samples during analysis (Brewer et al, 2002) hence the reason for using the Drager sampling system for hydrogen sulfide gas emissions in this study (Active Sampling Methodology) which proved to be more effective in quantitative analysis of odor as well as identification of various odorous compounds due to its ease of application and cost effectiveness. For instance results from the open loop control system UV-VIS Spectrometry analyzed gas samples gave mean concentrations for both ammonia and Hydrogen sulfide whereby for Open – loop liming, ammonia concentration was 98ppm and 112ppm for deliming, and Hydrogen sulfide concentration was 262ppm in liming and 88ppm deliming. In case of closed loop control system of beam house processing, there was no detection of both ammonia and Hydrogen

52

sulfide gas by the UV-VIS spectrometry. This is an indication that the closed loop control system of beam house processing was very effective. Communities surrounding tanneries are becoming more aware of the ills of molecular gas emissions from such entities, and not enough effort has been done in the past to address this problem (Nimmermark, 2004). The study looked at the accuracy of the UV-VIS analysis of gas samples both in the open loop and closed loop control system of liming. The major source of odor in tanneries usually emanates from the liming process hence the reason for determining the accuracy of the results of gas samples obtained from the beam house liming process step. Since we usually don’t get a lot of ammonia gas emissions during liming, the percentage accuracy for this gas was only 1.7% as compared to 2.6% from Hydrogen sulfide gas emission, which is expected to be relatively higher in liming (Table5). Due to this reason, the precision of the measuring instrument in case of ammonia (i.e UV-VIS Spectrophotometer) was higher (4.23%) as opposed to (3.39%) in case of hydrogen sulfide gas analysis, using the same instrument (UV-VIS Spectrophotometer), as indicated in Table 4.6. Conventional beam house processing does not require close monitoring as beam house process steps have a wide margin of error. However, there is reduced efficiency and effectiveness of the entire open-loop control system of beam house processing (Ziff, 2007). The experimental data and readings obtained from the determination of ammonia concentration in odor samples using the Nessler’s spectrophotometric method, were collected and analyzed as indicated in the information given in Figures 4.1 and 4.2. It was found that the closed loop control system of deliming had a relatively very high performance (i.e. both in

53

efficiency and effectiveness of the process) in the removal of odorous ammonium components from gas streams in tannery delime liquors. From the results, it was found that, the efficiency of closed loop control system of deliming in terms of ammoniacal odor reduction increased from about 64.3% in the open-loop control system of deliming to 84.3% in the closed-loop control system (Figures 4.1 and 4.2). The calculations were done from the following absorbance values as observed from the Nessler’s determination method of ammonia concentration: -

Absorbance value for the blank solution in open-loop control system of deliming = 0.18ppm.

-

Absorbance value for the sample solution in the open-loop control system of deliming = 0.28ppm. Thus, 0.18/0.28 x 100 = 64.3%

-

Absorbance value for the blank solution in closed-loop control system of deliming = 0.001ppm.

-

Absorbance value for the sample solution in closed-loop control system of deliming = 0.005ppm. Thus, the concentration of ammonia in the closed-loop control system was only 0.001/0.005 x 100 = 20%. Therefor, the increase in both efficiency and effectiveness of the closed-loop control system of deliming as opposed to the open-loop control system of deliming was 64.3% + 20% = 84.3%.

54

5.0 CONCLUSION AND RECOMMENDATIONS 5.1 CONCLUSION In the present study it has been ascertained that there has been no effective technology of eliminating or reducing the odor menace in tanneries particularly in the beam house. So in this investigation, it was found that the closed loop control system carried out in the study was effective in controlling odor emanating from Hydrogen Sulfide gas and mercaptans, as evidenced by the zero values obtained from the GC – MS analysis of samples sourced from the liming process step (Table 4.2). The drager sampling system of Hydrogen Sulfide gas carried out in this study proved to be more effective in quantitative analysis of odor as well as identification of various odorous compounds due to its ease of application and

55

cost effectiveness. This method was so effective that in the closed loop control system there was no detection of both Ammonia and Hydrogen Sulfide gas by the UV – VIS Spectrometry as opposed to the open-loop control system, which gave 98ppm of Ammonia concentration values in liming and 112ppm for deliming. Likewise the method gave concentration values of Hydrogen Sulfide gas as 262 ppm in liming and 88ppm in deliming. Since we usually don’t get a lot of ammonia gas emissions during liming, the percentage accuracy for this gas was only 1.7% as compared to 2.6% from Hydrogen sulfide gas emission, which is expected to be relatively higher in liming (Table4.5). Due to this reason, the precision of the measuring instrument in case of ammonia (i.e UV-VIS Spectrophotometer) was higher (4.23%) as opposed to (3.39%) in case of hydrogen sulfide gas analysis, using the same instrument (UV-VIS Spectrophotometer), as indicated in Table 4.6. From the results, it was found that the efficiency of closed-loop control system of deliming in terms of ammoniacal odor reduction increased from about 64.3% in the open-loop control system of deliming to 84.3% in the closed-loop control system (Fig 4.1 and 4.2) Analysis of variance (ANOVA) of the colorimetric determination of H2S in samples obtained from both the open loop and closed-loop systems of liming (Table 4.8) is given in table 4.9. It was found that the regression between the absorbance values (response) and factors (model/ experiment) was reliable due to the high correlation coefficient (R=0.888) and very low P value (0.025) of the regression. This P value indicated that the variation was mainly (about 88.8%) due to the variation in the factor levels. Among the linear terms the concentration of Hydrogen Sulfide (H2S) in samples obtained from the open loop control

56

system of liming was found to be highly significant as is reflected in the very low calculated P value (0.004) and high statistics.

5.4 RECOMMENDATIONS Tanneries should incorporate and practice the closed-loop control system in the tannery beam house as it reduces the level of odor emitted. Soaking and liming should be done in airtight drums instead of paddles as this helps in controlling odor emissions. To reduce odor due to raw materials, proper storage practices should be encouraged like cleaning the raw materials before storage and curing. From the study and related conclusions, the researcher recommends that further studies should be taken to assess the economic benefits of odor reduction in the tannery beam house. Further studies should also be taken to reduce toxic emissions from subsequent stages in the Tannery.

57

6.0 REFERENCES B. Clemenc and A. Gantar (1995): Odor control in leather production, Journal of the society of leather Technologists and Chemists. Vol 80 pg 11. Battye, R; Battye, W; Overcash, C; Fudge, S; 1994. Development and selection of ammonia emission factors; 68 – D3- 0034; US environmental Protection Agency, Washington DC. Bethea, Robert M. (1973), Comparison of Hydrogen Sulphide analysis techniques, Journal of the Air pollution control Association. Vol 23, No.8, pp710-713. Bowker, R.P.G; J.M. Smith and N.A.Webster, (1989). Odor and corrosion control in sanitary sewerage systems and treatment plants, Noyes Data corp, N.J; USA. Buonicore, A.J and W.T Davis (1992), Air pollution engineering manual, air and waste management association Van Nostrand Reinhold, N.Y.

58

Burns, R. T; Armstrong, K.A; Walker, F.R; Richards, C.J; Raman, D.R; 2003. Ammonia emission from a broiler production facility in the United States. In Proc. International symposium on Gaseous and Odor Emissions from Animal Production facilities, 88-95. Horsens, Denmark. CIGR. Charles M. McGinley, Michael A. McGinley, Donna L. McGinley (2000): Odor Basics, Understanding and using odor testing. Claudia C. (2006). Air quality issues and animal agriculture; A prime CRS report for congress. Dr. Fazli Akyuz ([email protected]) Odor: An Important Problem in Leather Industry. E. Lahman and K.E Prescher, Wasser Luft, Beir, 1968:520(1968) as cited in chemistry (1969). EPA, 2000; Guide to field storage of Zoo solids and other organic Byproducts in Agriculture and Soil resource management, US – EPA. Evi – chan Jeon, Hyun-Keur Son and Jaee – Hwan Sa. (2009): Emission characteristics of selected odorant compounds at a waste water treatment plant.

Sensors

ISSN

1424-8220.

PP

312-326,

www.mdpi.com/journal/sensors. Groot, K.; Speelman, L; Metz, J.H.M; (1998) ; Litter composition and ammonia emission in aviary houses for laying hens; Journal of Agricultural Engineering Research; 70, 119-129. Hinz T; Linke S; 1998, A Comprehensive experimental study of aerial pollutants in and emissions from livestock buildings. Journal of Agricultural Engineering Research 70, 119- 129

59

Holger, K; Martin E;

John M. (1998), Ammonia emissions from

Agriculture; Journal of Nutrient Cycling in Agro ecosystems; 51, 1-3. IUE – 8: Recommendations of odor control in Tannery (2008 updated Document) J.A. Zahn et al, (2000): Correlation of Human Olfactory responses to airborne concentrations of Malodorous Volatile organic compounds emitted from swine effluent, Journal of Environmental Quality vol. 30, No. 2, pg 624 – 634. Kalman, E.L; Lofvendhal, A; Winquist, F; and Lundstrom, I; 2000, classification of complex Gas mixtures from Automotive Leather using and electronic nose, Analytica Chemica ACTA. Kenya Subsidiary legislation (2014): First schedule page 227. Leonardos, G.D Kendal and N. Bernard, (1969). Odor thresholds determinations of 53 odorount chemicals. Air pollution control association. J. 19(2): 91-95. M.B. Jacobs, Air pollution control Association 15:314 (1965) M.B. Jacobs, M.M,Braverman, and S. Hochleiser, Analytical Chem 29;1349 (1957). M.Susan Brewer and Keith R. Cadwallader (2002): Overview of odor measurement techniques. N. Akdeniz, L.D. Jacobson, B.P.Hetcher, S.D.Bereznicki, A.J. Heber, J.A Keziel, L.Cai, S.Zhanz, D.B.Parker (2012); Odor & odorous Chemical Emissions from Animal Buildings; Part 4: Correlations between sensory & chemical measurements; http://lib.dr.iastate.edu/abe_eng_pubs/238

60

Nimmermark S. (2004): Odor impact – odor release, Dispersion and influence of Human well being with specific focus on Animal Production, Doctoral Thesis, Swedish university of Agricultural sciences, Alnarp60p. Rames C. Panda , Chokalingana Lajpathi Rai, Ventkatasubramaniam Sivakumar, Asit Baran Mandai (2012): Odor removal in leather tannery. Ruth J.H (1986). Odor thresholds and irritation levels of several chemical substances; A142-A151. S. Fukui, S. Naito, M. Raneko, and S.Kanno, Eisei Kagaku 13(1); 16 (1967) as cited in Chem abstract. 68:52991 (1968). Verschueren, K (1996). Handbook of environmental data on organic chemicals 3rd edition Van Nostrand Reinfold, N.Y 2064P. Yuwano A. and Lammers P.S (2004): Odor pollution in the environmentand the detection instrunmentation, Agricultural engineering international; The GCIGR Journal of scientific research and development. Invited overview paper vol VII. Zhang, Q, Feddes, J.J.R; Edeogu, I.K and Zhou, X.J.2002. Correlation between odor intensity assessed by human assessors and odor concentration measured with olfactometers. Canadian biosystems Engineering 44: pp 627632.

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APPENDIX 1: PROCESS

RECIPE

FOR

CONVENTIONAL

(OPEN-LOOP)

BEAMHOUSE

PROCESSING. MATERIAL: Wet salted goat skins

DATE:

PIECES: 3

WEIGHT:

PROCESS

CHEMICAL

%

TEMP0C

TIME

COMMENTS

SOAKING

WATER

300

25

RUN

Check PH, Check Baume. Drum

(DIRT

45 MINS speed 1-3rpm,

SOAK)

TAKE

GAS

SAMPLE.FOR

ODOR ANALYSIS MAIN

WATER

300

SOAK

Na2S or

0.2

Na2CO3

or 0.5

Soaking enzyme

0.5

62

Biocide

0.2

RUN

Check PH (9-10), Check Baume

6Hrs

(20Be’) Drain, offload,Green flesh.

LIMING

WATER

80

20

Na2S

1

Antiwrinkling

1

RUN 45’

2-3 rpm

1

RUN

Leave overnight

agent(Felliderm LPD LIQUID) Na2S

2HRS Na2S

0.5

Lime

3

RUN 30’

Water

60

Run 60’

Water

60

Run 60’

Run

drum(10’every

hour)for

18hrs. TAKE GAS SAMPLE FOR ODOR ANALYSIS Drain and offload. Lime flesh & weigh. Wash

Delime wash

Water

200

20

RUN 15’

Drain

Water

200

20

RUN 15’

Drain

Water

200

35

Ammonium

0.5

RUN 10’ x 2

sulphate/chloride Sodium

0.2

RUN 30’

Drain

RUN

TAKE GAS SAMPLE, FOR

1 hr

ODOR ANALYSIS.

Metabisulfite Delime

Water

200

Ammonium

2

35

Sulfate Sodium

0.75

Metabisulfite

CUT, Check PH (PH 8.2 – 8.5). Phenolpthalein turns colorless to indicate that deliming is complete.

63

Bating

Bate

1

Washing

Water

200

Water Pickling

RUN 1hr

Drain

Cold

RUN 15’

Drain

200

Cold

RUN 15’

Drain

Water

80

20

Salt

8

Check Baume (60Be’) RUN 30’

Formic acid (Dil 0.5 1:5

with

cold

water) Sulfuric acid (Dil 1.25

RUN

Leave overnight

1:10

120’

Check PH (2.5 – 2.8)

with

cold

H2O)

APPENDIX 2: CLOSED LOOP CONTROL SYSTEM FOR BEAMHOUSE LEATHER PROCESSING. MATERIAL: WET SALTED GOAT SKINS

DATE:

PIECES:

WEIGHT: (ALL OFFERS CALCULATED ON SALTED WEIGHT)

PROCESS

CHEMICAL

%

TEMP0C

TIME

COMMENTS

SOAKING

WATER

220

25

RUN

Check PH, Check Baume. Drum

(DIRT

Wetting agent

0.2

2 hrs

speed 1-3rpm,

SOAK)

(if too dirty)

MAIN

WATER

220

SOAK

Na2S or

0.2

Na2CO3

or

Drain 25

64

0.5

Soaking enzyme

0.5

Biocide/sodium

0.2

RUN 8- Drum1-3rpm,

phentachlorophen

10Hrs

ate

TAKE GAS SAMPLE FOR ODOR ANALYSIS Check PH (9-10), Check Baume (20Be’) Drain, offload,Green flesh, trim & weigh.

Washing

LIMING

WATER

250

25

RUN 40’

Drain

WATER

250

25

RUN 40’

Drain

WATER

80

20 - 25

Na2S

1

Antiwrinkling

1

RUN 45’

2-3 rpm

RUN

Drum speed 2-3rpm,

2HRS

TAKE GAS SAMPLE FOR

agent(Felliderm LPD LIQUID) Hydrogen

4

Peroxide Na2S

1

ODOR ANALYSIS. Check PH (12.5) Leave overnight

65

Hydrogen

2

peroxide Na2S

0.5

Lime

3

RUN 30’

Water

60

Run 60’

Water

60

Run 60’

TAKE GAS SAMPLE. Run

drum(10’every

hour)for

18hrs. Drain and offload. Lime flesh & weigh. Wash

Water

200

20-25

RUN 15’

Drain

Water

200

20

RUN 15’

Drain & offload, Lime flesh & weigh (offers calculated on limefleshed weight)

Delime wash

Water

200

Ammonium

0.5

35

sulphate/chloride Sodium

RUN 30’

0.2

Metabisulfite Delime

Water

200

Ammonium

2

35

Sulfate Sodium

0.75

Metabisulfite

66

Drain

Boric acid

1

Run 1hr

TAKE GAS SAMPLE FOR ODOR ANALYSIS. CUT, Check PH (PH 8.2 – 8.5). Phenolpthalein turns pink btwn PH 8&9

Bating

Bating

enzyme 1

RUN 1hr

Check PH (8.2) pheolpth turns

(add to deliming

pink, & thumb impression on pelt,

bath)

should retain thumb impression & air trapped in a loop should come out freely on squeezing the pelt. Drain

Washing

Pickling

Water

200

Cold

RUN 15’

Drain

Water

200

Cold

RUN 15’

Drain

Water

80

20

Salt

8

Formic acid (Dil 0.4 1:5

with

Check Baume (60 –70 Be’) RUN 20’

cold

water) Sulfuric acid (Dil 1.25

RUN

Leave overnight

1:10

120’

Check PH (2.5 – 2.8), both liquor

with

cold

H2O)

& cross-section (use bromocresol green).

67