3. CHARACTERISTICS OF TANNERY EFFLUENTS IN TIRUCHIRAPPALLI DISTRICT

Transcription

1 3. CHARACTERISTICS OF TANNERY EFFLUENTS IN TIRUCHIRAPPALLI DISTRICT 3.1 INTRODUCTION The conventional leather tanning technology is highly polluting as it produces large amounts of organic and chemical pollutants. In general, waste materials of tanning industries are categorized into solid waste and liquid effluent; the solid wastes include salts, unhairing wastes, lime wastes, flesh, myrob dust, buffing dust and trimmed waste. Some portions of these solid wastes are sold to outside agency for further beneficiary uses. The remaining solid waste is stored in heaps within the tannery premises. The generated liquid waste is let out to surrounding land without proper treatment. These effluents cause severe damage to the flora and fauna (Mariappan et al., 1997). This industry in developing countries is mostly run as a cottage /smallscale industry with a very few medium sized units. The lack of awareness in the modern industrial practice has resulted in the discharge of effluent which exhibit very high amounts of protein, chlorides, trivalent chromium, nitrogen, Sulphate, COD, BOD, and suspended solids (Kadam, 1990). The tannery operations consist of transforming the raw hides, a highly putrescible material, into leather, a stable product which can be conserved indefinitely and has a significant value (Suresh et al., 2001). These operations follow a sequence of chemical reactions and mechanical processes using specialized machinery. Among these, tanning is the fundamental stage which confers to leather its stability and essential characteristics. Only chromium (III) 33

2 sulphate possesses tanning proprieties with respect to skin collagen. To obtain good quality leather, it is necessary to use a quantity of chromium salts representing 2 to 2.5% (calculated as Cr 2 O 3 ) pf the mass of skins to be tanned (Rao et al., 2002). These pollutants, which are mostly contained in the effluent discharged by tanneries, are a serious threat to the environment. The tannery effluent, if not treated properly, can cause serious damage to soil and water bodies. The high amount of salt contained in the effluent, for example, can increase soil salinity, reduce fertility and damage farming in large areas. Tanneries also produce harmful gases, dust and a large amount of solid waste. The groundwaters in the vicinity of tanneries of Pallavaram, Chrompet, Ambur, Ranipet, Pernampet, Vaniyambadi, Dindugal and Tiruchirappalli have been found to be deteriorated in quality. At Ambur well water has TDS ranging from 1200 mg/1 to 6000 mg/l. Subsurface water of Palar at Vaniyambadi has TDS and chlorides of about 2000 mg/1 and 800 mg/1 respectively (Sastry, 1984). When tannery effluent-gains access to cultivable lands or when the lands are irrigated with effluent, the fertility of the soil is affected, it changes the characteristics of soil and interferes with intake of water by plants. Presence of chromium influences the metabolic processes of plants (Devarajan et al., 1993). Appa Rao et al. (1991) studied the extent of pollution of ground water sources in and around the tannery units located in Dindigul town and reported that the 34

3 parameters like total solids, hardness and chlorides in the ground water sources are higher than the admissible limit for drinking water. In Tiruchirappalli tanneries are clustered at Sempattu area and their waste water had been discharged without proper treatment upto The supreme court of India by its order dated and issued direction for the closure of tanneries which had not installed Effluent Treatment Plant (ETP) individually or collectively. Thereafter all the tanneries established their own ETP or common Effluent Treatment plant (CETP) for the tannery waste water treatment. Main objective of the present study was to characterize the tannery effluents of Tiruchirappalli district, with particular attention to their physicochemical and biological properties. Ground water quality was also checked in and around the cluster of tanning industries situated around sempattu, Tiruchirappalli to confirm the pollution by tannery waste water MATERIAL AND METHODS Study Area The clusters of tanning industries are situated in the Sempattu area, south of Tiruchirappalli Railway Junction. These tanneries produce semi-finished vegetable tanned leathers. The ground water is the main source for various leather processing operations. About 350 M 3 /day waste water is generated from different processing units of the industry. In the present study the ground water quality was also checked in and around the cluster of tanning industries at Sempattu. There are 11 tanneries functioning in Sempattu. The ground water 35

4 sampling area of the village Sempattu for the present study was located at a distance of 1.5 km from the tanning industries. This village has 2 hand pumps, 6 open wells and 4 bore wells Collection of Effluent Samples For the present study, effluent was collected from a tannery at Sempattu, Tiruchirappalli District, Tamilnadu, India. The effluent samples were collected raw from the composite stream. The effluent was collected in polythene containers [2 litre capacity], and were brought to the laboratory with due care. The samples were collected for a period of 12 months from January 2008 to December Physico - Chemical Characteristics of Tannery Effluent The physico-chemical parameters such as colour, odour, temperature ph, Electrical Conductivity (EC), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Hardness, Magnesium Hardness, Calcium Hardness, Sodium, Sulphate, Chloride and Total Chromium were determined as per the methods mentioned in the Table 3.1 Sampling of ground water from Sempattu was carried out during Water samples were collected in polythene containers from hand pumps and bore wells after running them for 15 minutes. All samples were refrigerated in laboratory at 4 C. Background information regarding the location of hand pumps, open wells and bore wells were recorded. The physico-chemical parameters such as ph, total alkalinity, total hardness, chlorides, total dissolved 36

5 solids, turbidity, dissolved oxygen, chemical oxygen demand and biochemical oxygen demand were analysed. The ph of the water was measured using a digital ph meter (Elicomodel No. LI120). The dissolved oxygen was estimated at the site of collection following Winkler s method (APHA, 1989). Turbidity was estimated using Nephelo turbidity meter (Systronics Model No. 131) and the results were expressed in Nephelo Turbidity Units (NTU). Estimation of remaining parameters was made following the methods described by Trivedi & Goel (1984).The methods of analysis for various parameters are listed in Table RESULTS Physico-Chemical Characteristics of Tannery Effluent Analysis of physico-chemical characteristics of the tannery effluent for a period of 12 months (from January 2008 to December 2008) has been studied and their results are given below Colour and Odour The colour of the tannery effluent was grey when observed visually and the odour,disagreeable (Table 3.2) ph The ph of the tannery effluent during the period of study is shown in table 3.2 and it ranged between 5.8 and 6.6. The lowest ph 5.8 was observed during the month of April 2008, where as the highest ph, value was 6.6 during November 2008, indicating thus the acidic nature of the tannery effluent. 37

6 Electrical Conductivity (pmhos / cm) (Table 3.2). The values of EC were found to be between and pmhos/cm Total Suspended Solids TSS level of the tannery effluent during January 2008 and December 2008 are depicted in table 1. In this study the TSS level ranged between a minimum of 1650 mg/l to a maximum of 1785 mg/l Total Dissolved Solids The TDS level ranged between a minimum of 2100 mg/l to a maximum of 3190 mg/l which is beyond the permissible limit (Table 3.2) Biochemical Oxygen Demand BOD level of the tannery effluent during the period of study is given in table 3.2. In this study, BOD ranged between a minimum of 830 mg/l to a maximum of 940 mg/l Chemical Oxygen Demand COD of tannery effluent January 2008 and December 2008 are depicted in table 3.2. The COD level ranged between a minimum of 2380 mg/l to a maximum of 2500 mg/l. 38

7 Total Hardness Total hardness of tannery effluent during the period of January 2008 and December 2008 is shown in table 3.2. Total hardness ranged between a minimum of 1400 mg/l to a maximum of 1700mg/L Calcium Hardness Levels of calcium in the tannery effluent during the period of January 2008 and December 2008 are depicted in table 3.2 and calcium level ranged between a minimum of 420 mg/l to a maximum of 520 mg/l Magnesium Hardness Levels of magnesium hardness in the tannery effluent during the period of January 2008 and December 2008 are depicted in table 3.2. In this study, the magnesium level ranged between a minimum of 251 mg/l to a maximum of 289 mg/l Sodium Sodium levels in tannery effluent estimated between January 2008 and December 2008 are depicted in table 3.2. The sodium level ranged between a minimum of 1260 ppm to a maximum of 1400 ppm Chloride Levels of chloride in the tannery effluent collected during the period of January 2008 and December 2008 are depicted in table 3.2 and the chloride levels ranged between a minimum of 1620 mg/l to a maximum of 1760 mg/l. 39

8 Sulphate Sulphate in tannery effluent during the period of January 2008 and December 2008 is shown in table 3.2. Sulphate ranged between a minimum of 1390 mg/l to a maximum of 1460 mg/l Biological Characteristics Among the biological characteristics, total heterotrophic bacterial population (THB) was monitored during the course of study from January 2008 to December 2008 Total Heterotrophic Bacteria (THB) THB population did not show any significant variation in the tannery effluents during the one year of study and almost similar levels of THB were recorded. THB varied from a minimum of x 10 7 / 100 ml in the month of April 2008 and a maximum of x 10 7 / 100 ml in November Heavy Metals Heavy metals present in the tannery effluent during the period of January 2008 and December 2008 is shown in table 3.2. Zinc level ranged between a minimum of 1.16 mg/l to a maximum of 1.36mg/L. Levels of copper in the tannery effluent ranged between a minimum of 1.24 mg/ml to a maximum of 1.39mg/ml. Iron level ranged between 4.47 mg/ml and 4.62 mg/ml. Manganese ranged between a minimum of 2.40 mg/ml and a maximum of 2.50 mg/ml. Chromium level was between 0.51mg/ml and 0.58 mg/ml. 40

9 Ground Water Quality To study the impact of tanning industry on the ground water quality, water samples were collected from different ground water sources from Sempattu. Details of the sampling of ground water in and around tanning industries of Tiruchirappalli are given in Table 3.4. Details of ground water sampling stations of Sempattu village are presented in Table 3.5. Water quality parameters of ground water samples for Sempattu village was analysed and the results are presented in Table 3.3. Table 3.4 shows the details of sampling of ground water in and around the cluster of tanning industries. The total number of tanneries in the study area is 7. Total number-of sampling points including hand pumps, open wells and borewells at Sempattu is 12. Table 3.5 provides information of ground water sampling stations in Sempattu and their distances from Tanning industries. The samples were collected from the ground water source such as hand pumps that were located about 50m from the tanning industries. The open wells (6) sampled from the present study were located at variable distances from the tanning industries (200 m to 500 m) and the bore wells (4) ( 300 m to 500 m). Table 3.3 provides data on the water quality parameters such as ph, Total Alkalinity (TA), Total Hardness (TH), Chlorides (Cl), Total Dissolved Solids (TDS), Turbidity (NTU), Dissolved Oxygen (DO), Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) of the water samples collected from the hand pumps, open wells and borewells of the Sempattu village. Various 41

10 water quality parameters measured in the water samples collected from the hand pumps, open wells and borewells of Sempattu did not show any remarkable variation with respect to the type of water source (HP, OW & BW). The ph ranged from 6.49 to 6.75, TA 420 to mg/l, TH 450 to 480 mg/l, Cl 4430 to 480 mg/l, TDS 810 to 830 mg/l, Turbidity 21.9 to 2.13 NTU, DO 2.4 to 2.7 mg/l, COD 12.2 to 13.8 mg/l and BOD 5.1 to 5.6 mg/l. 3.4 DISCUSSION Leather industry has today attained well-merited recognition in the international market, besides occupying a place of pride among the top exporters of the country. This industry provides direct and indirect employment to around 2.5 million persons and is one of the major foreign exchange earners for the country (exports of US $ million) thereby contributing significantly to the Indian economy (16th Indian International Leather Fair 2001, CLRI) and generates effluent which is estimated to be about 75,000 m 9 day (Sahasranaman and Buljan, 2000), while Jawahar et al., (1998) estimates that the wastewater discharged from these tanneries range from 80,000 to 1,00,000 m 3 /day. Tannery effluent is highly polluted with high concentration of protein, chlorides, trivalent chromium, sulphate, COD, BOD, TSS, TDS etc (More et al., 2001). Processing of skins and hides require large amount of water and generate huge quantities of tannery effluent which is discharged indiscriminately into nearby fields either treated or untreated. Water and land pollution problems related to tannery effluent have been reported as a serious problem in many countries (Sahasranaman and Buljan, 2000). There are reports of chromium recovery but the major issue like TDS, TSS, BOD and COD are still an unsolved misery to the tanneries. 42

11 The present study on the tannery effluent from Tiruchirappalli district was aimed at analyzing the characteristics of tannery effluent and to study the nature of pollutants present in the tannery effluent. In the present investigation, the physico-chemical characteristics of the untreated tannery effluent has revealed that it is acidic, with high BOD, COD, organic particulate matter, unpleasant odour and colour. The raw effluent was dark ash coloured, and the colour may be derived from tanning sub-process such as bating, pickling, neutralisation, dyeing and fat liquoring. According to Clayton and Clayton (1981), dyeing is one of the major causes for development of colour in the effluent. Unpleasant odour may be due to microbial growth or may be due to decomposition (Panneerselvam, 1998). Microbial load of the effluents was heavy and well above seven log number irrespective of the months of analysis. Moreover a large number of pollutants can impart colour, taste and odour to the receiving waters, thereby making them unaesthetic and unfit for any use (Goel, 2000). The ph of the tannery effluent was highly acidic (5.8 to 6.6) and did not meet the general standards recommended by CPCB (1995) for the discharge of effluents into inland surface water or for irrigation purposes. Discharge of untreated effluents with such a low ph into ponds, rivers or on lands for any purpose may be detrimental to soil fauna and aquatic biota such as zooplankton and fishes, since low ph level may affect the physiology of fishes (From, 1980, Geetha et al., 1996). Further the toxicity of certain substances present in water may be enhanced due to their interaction with the low level of ph prevailing, which may further be detrimental to the aquatic organisms (McCaull and Crossland, 1974). 43

12 Electrical conductivity is a numerical expression of the ability of water sample to carry an electric current. The number depends on the total concentrations of the ionised substances dissolved in water and to the temperature at which the measurement is made. The conductivity of tannery effluent in the present study was very high during most of the months, but it was highest, during April, July and November High level of conductivity may be due to the presence of inorganic substances and salts which show good conductivity (Robinson and Stokes, 1959). It may be pointed out that, amount of salts added while processing the hides and skins differs from tannery to tannery and also on the type of processing. The reason for the highest electrical conductivity during April, July and November 2008 may be due to quantity of skins and hides processed and the amount of salts used. According to Kataria et al., (1995) high electrical conductivity level may be due to higher concentration of acid-base and salt in water. High level of total suspended solids (Table 3.3) present in the tannery effluent could be attributed to their accumulation during the processing of finished leather. Moreover, presence of total suspended solids leads to turbidity resulting in poor penetration of light in the aquatic system, thereby curtailing the light for photosynthetic activity (Goel, 2000). Further the settling of suspended particles on soil and soil fauna, might lead to various damages like change in soil porosity, soil texture, water holding capacity on one hand (Narasimha et al., 1999) and clogging of gills and respiratory surfaces of fishes on the other hand 44

13 (Alabaster and Lloyd, 1980). TSS in effluents may affect fisheries - directly, thereby destroying bottom fauna necessary for fish as food or reduce the spawning ground of fisheries. The composition of solids present in tannery effluent mainly depends upon the nature and quality of hides and skins processed in the tannery. High level of total dissolved solids may be due to high salt content. The total dissolved solids level was found to exceed the permissible limit of 2100 mg/i prescribed by the CPCB (1995). According to Goel (2000), high level of TDS in the effluent renders it unsuitable for irrigation. According to Manivasakam (1984a), high amount of total dissolved solids-recorded in the tannery effluent could be attributed to processes like soaking, liming, dehairing, defleshing and deliming. Biochemical. Oxygen Demand is one of the important parameters used in water pollution studies to evaluate the impact of wastewaters on receiving waters (Subbarao and Gadgil, 1996). The present study has revealed that the high levels of biological oxygen demand in the tannery effluents ( mg/1) indicating high organic load. Present investigation is in agreement with the studies on tannery effluent (Gokulakrishnan, 2003), sugar mill effluent (Bhatnagar et al., 1986), sago effluent (Panneerselvam, 1998) and distillery effluent (Prabakar, 1999). According to Poole et al. (1978), increase in BOD is a reflection of microbial oxygen demand, which leads to depletion of dissolved oxygen which may cause hypoxic conditions with consequent adverse effects on aquatic biota. 45

14 Under such a condition no aquatic life can survive, except anaerobic microorganisms. Further the presence of organic matter will promote anaerobic action leading to the accumulation of toxic compounds in the water bodies (Goel, 2000). Chemical Oxygen Demand is the best method of organic matter estimation and is a rapid test for the determination of total oxygen demand by organic material present in the effluent. In the present investigation, high level of COD was recorded ( mg/l) and these values did not meet the standard prescribed by CPCB (1995) for effluent discharge into inland surface water (permissible COD level 250 mg/1). This indicates that the effluent is unsuitable for the existence of the aquatic organisms, due to the reduction in the dissolved oxygen content. Raj et al. (1996) recorded higher values of COD for the treated tannery effluent of Chrompet (Chennai - India), and concluded that high COD might be due to vegetable tannins and non-tannin which would increases the COD. Further high COD may be due to high amount of inorganic compounds which were not affected by the bacterial decomposition (Nagarajan and Ramachandramoorthy, 2002) Ions especially calcium, sulphate, magnesium and sodium impart hardness to water. The values obtained for the tannery effluent reveal that the concentrations of ions were more than the prescribed limit by CPCB (1000 mg/l). The hardness of water and high concentration of salts may produce scaling in boilers, corrosion of machinery and result in degraded quality of the product (Goel, 2000). Moreover high salt content will deposit salts, resulting in scaling of the equipment thus resulting in higher energy cost to the industry. 46

15 According to Lehr et al. (1980), the water is very hard if the value is beyond 180 mg/l. In the present study the value ranges between mg/l which indicated that the water hardness was very high. According to Goel (2000), high concentration of salts (3000 mg/l) produces distress in cattle and livestock, hence the tannery effluent should not be released into inland or surface land, without adequate treatment. High levels of chlorides in the tannery effluent could be attributed to the soaking process involved (Athappan et al., 1992). More over high content of calcium, magnesium, sodium, chlorides, sulphates, hardness present in the tannery effluent might be due to mixing of tannery effluents with the aqueous system from the different sources of processing within the tannery. Acidic ph, excessive hardness, high TSS, TDS, BOD, COD of the tannery effluent revealed that, the tannery effluent was highly polluted and it has to be treated, but reports indicate that even the treated effluent do not satisfy the prescribed limits of the CPCB (1995). Hence it is imperative to adopt technologies that could reduce or degrade the tannery effluent effectively. According to McEldowney et al. (1993), the most appropriate method for pollution control depends on various factors linked to the nature and type of pollution with environmental statutes, cost benefit analysis and commodity acceptance, Since no single technology can satisfy all these requirements, combined treatment strategies could be a wise and prudent option. Chromium is a heavy metal which is widely used leather tanning industries. Trivalent and hexavalent chromium compounds are predominant, 47

16 having various industrial applications (Dugan, 1972). There are many ways by which chromium is released into the environment. It is one of the constituents in effluents from a large number of industries, particularly the tanning industries and this creates a potential threat to aquatic organisms. The chrome tanning method is most widely used process in the tannery industries located in Ambur, Vaniyambadi, Pernambut and Ranipet zones of the Vellore district. However, the vegetable tanning method is practiced in the tanneries located at Tiruchirappalli district. All the heavy metals reported in the effluent are at very low concentrations and satisfy the prescribed limits of the CPCB (1995). Leather industries use about seventeen different kinds of tanning substances but chromium is the most commonly used tanning agent (Venier et al., 1985). Nearly 90% of all leather produced is tanned using chromium. In chrome tanning process chromium actually cross links the collagen fibres and thus decreases the porosity of the leather (Kathrine and Schwedt, 1994). The ground water quality has been studied in Sempattu area of Tiruchirappalli. Tiruchirappalli is the one of the active centres of Tanning Industries and it occupies fifth rank among Tanning Industry of the state, next only to Ambur, Vaniambadi, Erode and Dindigul. Of the 13 tanning industries in Tiruchirappalli 7 tanneries are located in and around Sempattu as a small cluster. They fall under the category of small scale tanneries. The tanning capacity of each industry is about 2 tonnes of skins and hides. They produce semi finished skins and hides by following the method of East-Indian Tanning or vegetable tanning. The tanning processes release huge volumes of effluent which has a 48

17 high oxygen demanding wastes and dissolved solids. After Supreme Court Judgement (May, 1995), all the tanneries established their own individual Effluent Treatment plant or CETP to treat waste water arising from tannery. However the impact of untreated tannery effluent released prior to the establishment of ETPs on the ground water sources has not been studied so far. Hence the present study is undertaken with the primary objective of assessing the impact of tanning industry on the quality of ground water. 78 sampling points at different sources like hand pumps (HP1-HP13), Open wells (OW1 - OW34) and Bore wells (BW1-BW31) were selected around the cluster of tanning industries. Their sampling points are located in 6 villages situated at varying distance from the sources of pollution 0. 5km km. The physico-chemical parameters, such as ph, Total alkalinity, Total hardness, chlorides, Total dissolved solids, turbidity, dissolved oxygen, chemical oxygen demand and biochemical oxygen demand were analysed and the mean values for all the 12 sampling points are given in Table. Water quality parameters of the different sources of the same village did not show any significant variation. The ph value in the sampling source of hand pumps, open wells and bore wells in all the sampling points were in the range of 6.4 to Total alkalinity in the sampling source of hand pumps, open wells and bore wells of chosen villages around the cluster of tanneries varied from 297 to mg/l, TH 307 to 483 mg/l, Cl 262 to 460 mg/l, TDS 491 to 817 mg/l, NTU 1.1 to 2.1 mg/l, DO 2.3 to 4.66 mg/l, COD 3.3 to 13.6 mg/l and BOD 1.2 to 5.5 mg/l. The variation of water quality parameters like TA, TH, Cl and TDS in hand pumps, open wells and borewells of surrounding villages of tanning industries in Tiruchirappalli are given in Fig. 49

18 In Sempattu area possibly water flows faster from the sources eastwards and percolates into the ground and hence elevates the levels of various water quality parameters. The gradient in the pollutional status of sempattu village may be attributed to distance between sources of pollution and village. However, ground water quality of Sempattu had been severely affected. Among the parameters tested the levels of TA, TH, Cl and TDS were highly varying. The variation with respect to the parameters like ph, NTU, DO, COD and BOD were insignificant. By comparing the range of these values with Indian Bureau of standard (1991) for desirable drinking water quality parameters, ph and NTU were well within the standard and other parameters exceeded the desirable levels. The quality of ground water in the study area was not suitable for drinking purpose. From the generated data, it could be concluded that Sempattu village was more affected because most of waste water were generated there itself. The ground water pollution in Sempattu may be attributed due to two factors. One is the closeness to pollution source and another is geological gradient towards east. It is quite natural that water will always flow east in this region and hence Sempattu recorded a steep decline in ground water quality as compared to other villages. It could be concluded that the ground water of Sempattu was not safe to drink. The impact of tanning industries has declined the ground water quality only in this village Sempattu. This observation advocates the need for a thorough evaluation of the effluent treatment efficiency as existing at present and for an effective remediatory option. 50

19 Table 3.1. Components of the experimental programme and analytical techniques S.No Parameters Analytical Method Reference 1 ph ph Meter APHA, Electrical conductivity Conductivity bridge(0.920) APHA, Oil & Grease Gravimetric APHA, TSS mg/l Gravimetric APHA, TDS mg/l Gravimetric APHA, BOD BOD chamber (20) APHA, COD COD mantle APHA, Total Hardness Titrimetric APHA, Dissolved oxygen Titrimetric APHA, Total Alkalinity Titrimetric APHA, Calcium Flame photometer APHA, Magnesium Flame photometer APHA, Sodium Flame photometer APHA, Chloride Titrimetric APHA, Sulphate Spectrophotometric APHA, Heavy metal AAS (Varian Techtron) APHA, Total Heterotrophic Bacterial population (THBP) Pour Plate Technique (CFU)

20 Table 3.2. Physico-chemical analysis of tannery effluent from January 2008 to December 2008 Characteristics Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Colour Odour GREY COLOUR DISAGREEABLE SMELL ph Ec pmhos/cm TSS mg/l TDS mg/l BOD mg/l COD mg/l Total Hardness mg/l Calcium mg/l Magnesium mg/l Sodium mg/l Chloride mg/l Sulphate mg/l Total Heterotrophic Bacterial population (THBP) (x10 7 /100ml) Heavy Metals Zinc (mg/l) Copper (mg/l) Iron (mg/l) Manganese (mg/l) Chromium (mg/l)

21 Table 3.3. Water Quality Parameters of Ground Water Samples Collected from Sempattu Sources of Ground Water Hand Pump Mean ± SD Open well Mean ± SD Borewell Mean ± SD Sampling Station ph Total Alkalinity Total Hardness Chloride TDS Turbidity NTU DO COD BOD HP HP (Range) 435± ± ± ±7.07 2± ± ± ±0.41 Ow OW OW OW OW OW (Range) 431.7± ± ± ± ± ± ± ±0.13 Bw Bw Bw Bw (Range) 446.5± ± ± ± ± ± ± ±0.17

22 Table 3.4. Details of Sampling of ground water in and around Tanning Industries of Tiruchirappalli Sampling Area Tannery (No.) Hand Pump (No.) Open well (No.) Borewell (No) Total sampling points (No.) Sempattu Table 3.5. Details of ground water sampling stations in Sempattu Sampling Area Sempattu Groundwater Source Hand Pump Open Well Bore well Sampling Station Distance from Tanning Industry (m) HP 1 50 HP 2 75 OW OW OW OW OW OW BW BW BW BW 4 500