Seasonal Variations of Groundwater Quality in and around Dindigul Town, Tamilnadu, India

Mohamed Hanipha M* and Zahir Hussain A

PG and Research Department of Chemistry, Jamal Mohamed College (Autonomous), Trichirappalli, India

 
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Abstract

Dindigul is situated southwest of the state capital, Chennai. The town does not have underground drainage system. The study area is facing the problem of water pollution because of various industries. Tanneries are thickly situated in and around Dindigul town. The pollution is affecting large numbers of people and causing a detrimental effect upon their health. The aim of the present study is to assess the physicochemical parameters for the groundwater samples in summer and rainy seasons. Twenty groundwater samples collected from borewells in and around Dindigul town and subjected to physicochemical analysis. The results were compared with WHO standard. The obtained result revealed that the parameters such as EC, TDS, HCO3, Cl, K, PO4, BOD, COD, and DO exceed the permissible limit of WHO in most of the groundwater sampling stations in summer and rainy seasons. The groundwater samples were more polluted beside industrial area.

Keywords

Dindigul, Groundwater, Seasonal variation, Physico-chemical, Water quality

Introduction

Water is the precious gift of nature to all the living beings for sustenance. The suitability of water for domestic, agricultural and industrial purposes mainly depends on the chemical composition of surface and subsurface. Groundwater is the largest source of fresh water on the planet excluding the polar icecaps and glaciers. In India, 90% population depends on groundwater for drinking, domestic, agricultural and industrial purposes in several states. Several factors like discharge of agricultural, domestic and industrial wastes, land use patterns, geological formation, rainfall pattern and infiltration rate affect the quality of groundwater.

When the waste water of an industry is dumped into streams, it gets into natural sources and causes change in physicochemical composition of ground water which ultimately becomes unsuitable for human use. For a long time, Dindigul town has been a centre of the tobacco trade and a manufacturer of cigars. The study area is having sidco industrial park, paper, textile, tanning, plastic and steel industries. Tanneries are thickly situated in and around Dindigul town. At present more than 80 tannery units are well established. Processing of leather requires a large amount of fresh water along with various chemicals. Every 10 kg of raw skin tanned requires about 350 L of fresh water. Leather production involves the use of excessive water and so it generates large quantities of effluents and other wastes.

The pollution is affecting large numbers of people and causing a detrimental effect upon their health. During the past few decades, the groundwater is being contaminated and it’s giving rise to health problems and epidemics. Usage of the chemical fertilizers for agriculture and small scale industries falls heavily on the quality of the drinking water in the study area. Hence the present study has been attempted to determine the physicochemical characteristics of groundwater in and around Dindigul town in summer and rainy seasons.

Materials and Methods

Study Area

Dindigul town is located in the southern state of Tamilnadu between 10°18’ to 10°25’ N latitude and 77°56’ to 78°01’ E longitude. It is the administrative headquarters of the Dindigul district. Dindigul is situated 420 km southwest of the state capital, Chennai covering an area of 14.01 km2 and has an average elevation of 265 m (869 ft). Dindigul is located in the foothills of Sirumalai hills. The topography is plain and hilly with the variation resulting in climatic changes. The map of the study area is shown in Figure 1.

der-chemica-sinica-Map-study-area

Figure 1: Map of the study area.

Sampling Stations

S1. Central Bus Stand, S2. Dudley School, S3. Dindigul Government Hospital, S4. St. Mary’s School, S5. East Govindapuram, S6. Dindigul Taluk Office, S7. Mariamman Kovil, S8. Begambur Mosque, S9. District Treasury Office, S10. Annamalai Mills Girls HSS, S11. Government Industrial Estate, S12. Railway Station, S13. SP Camp Office, S14. MSP School, S15. St. Joseph Hospital, S16. Cauvery Water Tank, S17. Chatra Kulam, S18. West Ashok Nagar, S19. K.K Nagar and S20. Rockfort.

Sampling collection and analysis

Twenty groundwater samples were collected in and around Dindigul town, Tamilnadu, India for the present study. The sampling was done in summer and rainy seasons for three successive years (2012, 2013 and 2014). Groundwater samples were collected from bore well after discarding water for the first two minutes in 2 litre plastic container. Before collecting the sample, the containers were rinsed with distilled water and finally rinsed with the water sample to be collected. After that, the groundwater samples from different locations were sealed, labelled and then brought into the laboratory for detailed physicochemical parameters. All necessary precautions were taken during sampling and analysis. Preservatives such as conc. HCl and conc. H2SO4 were added to the samples. The collected groundwater samples were subjected to physicochemical analysis. The parameters such as pH, electrical conductivity, total dissolved solids, total hardness, carbonate, bicarbonate, chloride, sodium, potassium, calcium, magnesium, nitrate, sulfate, phosphate, fluoride, biochemical oxygen demand, chemical oxygen demand and dissolved oxygen were analysed. The standard methods of APHA [1] adopted for each parametric analysis of groundwater samples. The obtained results are compared with WHO (2011) standard of water quality parameters.

Results and Discussion

The groundwater samples were collected in and around Dindigul town. The obtained results are tabulated in Tables 1 and 2. The experimental results are compared with the limits recommended by WHO (2011) [2] and discussed as follows.

Stations pH EC TDS TH CO32- HCO3- Cl- Na+ K+ Ca2+ Mg2+ NO3- SO42- PO43- F- BOD COD DO
S1 6.7 1402 703 657 36 395 235 109 17 123 85 29 85 0.29 1.33 45 48 2.8
S2 7.2 1089 679 608 36 379 333 166 16 116 77 21 139 0.39 1.21 31 42 2.9
S3 7.4 1519 1122 601 30 433 416 195 14 177 39 26 146 0.43 0.94 20 43 4.8
S4 7.3 1223 815 505 33 427 167 118 70 90 69 25 167 0.61 1.47 43 45 4.0
S5 7.4 1290 877 451 48 162 137 67 94 85 59 19 164 0.39 0.76 50 26 4.2
S6 7.7 1048 782 569 30 511 148 126 22 99 78 19 51 0.23 0.78 68 45 3.1
S7 7.1 976 770 369 28 505 125 87 111 53 59 23 83 0.31 1.66 45 27 3.4
S8 7.5 2920 1720 481 24 290 328 183 26 78 70 21 53 0.79 1.43 46 34 4.0
S9 7.2 920 630 440 28 302 423 213 13 81 57 32 109 0.52 0.65 26 28 4.1
S10 7.4 761 497 793 21 324 541 123 21 143 104 24 39 0.25 0.84 23 31 4.1
S11 7.4 708 507 624 23 332 339 72 26 110 86 18 59 0.23 0.46 45 29 3.9
S12 7.5 945 661 510 28 266 218 99 10 92 69 24 94 0.29 0.29 29 29 5.2
S13 7.7 1043 744 483 29 288 215 104 13 94 62 23 94 0.54 0.89 24 27 5.5
S14 7.7 1084 729 525 18 305 289 135 20 113 59 38 105 0.39 0.15 50 33 3.5
S15 7.5 991 567 465 27 277 209 98 13 94 56 22 88 0.26 1.07 16 28 5.3
S16 7.4 1155 747 468 25 204 372 142 16 122 60 33 135 0.27 0.24 37 27 4.9
S17 7.6 1658 1041 573 36 202 381 146 14 121 64 38 87 0.50 0.28 34 39 3.2
S18 7.5 748 528 414 29 242 167 84 9 84 50 19 92 0.26 0.42 24 35 5.0
S19 7.5 1176 968 294 30 292 233 77 14 96 64 27 78 0.34 1.15 23 36 4.4
S20 7.7 1077 848 423 28 477 122 102 10 60 67 22 49 0.37 1.70 23 49 3.2

Table 1: The mean values of physicochemical parameters of groundwater samples during summer seasons (April 2012, 2013 and 2014).

pH

The mean pH values are recorded in the range of 6.7-7.7 and 6.8-7.8 for the groundwater samples during the summer and rainy seasons respectively (Tables 1 and 2). The pH values are within the permissible limit of 6.5-8.5 (WHO 2011) in all the sampling stations. There is no abnormal change in the pH in most of the ground water sampling stations in both summer and rainy seasons. The low pH does not cause any harmful effect [3]. The reaction of minerals in rocks with water, carbon dioxide and possibly organic matter such as Humic acid and Fulvic acid changes the pH of water [4].

Stations pH EC TDS TH CO32- HCO3- Cl- Na+ K+ Ca2+ Mg2+ NO3- SO42- PO43- F- BOD COD DO
S1 6.8 767 629 310 29 266 256 124 22 44 49 18 51 0.25 1.26 79 31 2.9
S2 7.2 1138 778 444 43 385 500 200 28 68 62 21 137 0.27 1.16 86 30 4.4
S3 7.1 1696 1115 352 34 281 358 212 7 36 55 30 158 0.36 0.52 64 19 5.3
S4 7.1 1612 1021 1070 52 335 711 175 29 164 158 28 131 0.58 1.37 68 34 3.9
S5 7.1 645 389 391 67 275 240 143 36 85 64 20 134 0.30 0.68 49 37 3.1
S6 7.6 547 361 193 28 317 85 59 78 26 33 18 36 0.22 0.58 70 39 2.6
S7 7.3 945 579 243 22 554 144 137 53 47 31 24 70 0.25 1.40 44 40 2.9
S8 7.5 1729 1129 676 15 552 580 354 89 84 112 26 90 0.69 1.61 45 35 3.2
S9 6.9 1820 1205 787 17 529 502 321 18 63 112 48 157 0.65 0.43 52 21 4.7
S10 7.3 1907 1210 965 30 365 659 251 26 127 129 41 128 0.48 0.68 41 19 5.3
S11 7.5 1406 902 898 20 302 434 138 23 124 94 35 104 0.21 0.36 46 45 3.2
S12 7.3 1000 665 602 14 355 272 139 43 65 45 29 76 0.38 0.21 45 27 4.7
S13 7.8 862 594 386 19 262 202 140 13 35 41 18 92 0.49 0.69 44 28 5.3
S14 7.8 1213 834 451 19 362 360 185 48 75 63 39 104 0.45 0.18 74 25 5.2
S15 7.2 952 585 416 17 342 240 152 20 48 59 27 106 0.21 0.67 46 26 5.5
S16 7.4 5472 3472 2070 15 391 2472 525 83 287 207 123 242 0.63 0.21 37 35 4.6
S17 7.4 603 366 352 57 238 295 318 28 72 38 34 77 0.26 0.24 53 43 3.2
S18 7.2 815 488 647 16 383 247 168 11 55 44 19 86 0.33 0.25 55 24 5.3
S19 7.2 1158 765 455 16 417 353 156 100 94 44 26 65 0.35 0.92 55 20 5.1
S20 7.3 674 517 301 21 422 163 142 76 20 31 19 45 0.26 1.52 65 25 4.6

Table 2: The mean values of physicochemical parameters of groundwater samples during rainy seasons (December 2012, 2013 and 2014).

Electrical Conductivity

The mean electrical conductivity values are observed in the range of 708-2920 μmhocm-1 and 547-5472 μmhocm-1 for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The EC values exceed the permissible limit of 600 μmhocm-1 (WHO 2011) in most of the groundwater sampling stations except at station S6 in rainy seasons. Electric conductivity of water relates to the total concentration of dissolved ions in the water. The high value of EC may be due to high concentration of ionic constituents present in the water bodies. EC is directly proportional to the total dissolved solids. Percolation of industrial wastes and intrusion of sewage may also enhance the high EC values in most of the sampling stations. The high value of EC may also be due to the due to the high dissolved solids [5].

Total dissolved solids

In the present investigation, the mean TDS values are found in the range of 630-1720 mg/l and 361-3672 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The TDS values exceed the permissible limit of 500 mg/l (WHO 2011) in most of the groundwater sampling stations in summer and rainy seasons. The higher concentrations are due to leaching of solid wastes from ground surface as well as enhanced seepage from domestic sewages. Maximum value of TDS is found at station S16 in rainy season. High level of TDS in this station may be due to the discharge from industries and untreated waste water [6]. The high level of dissolved solids may aesthetically unsatisfactory for bathing and living. Water containing high TDS concentration may cause laxative or constipation effects [7].

Total hardness

The mean total hardness values are found to be in the range of 369-793 mg/l and 193-2070 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The total hardness values exceed the permissible limit of 500 mg/l at sampling stations S1-S4, S6, S10-S12, S14 and S17 in summer and S4, S8-S12, S16 and S18 in rainy seasons. The high value of TH is observed at station S16 in rainy season. Percolation of industrial wastes and domestic wastes enhance the TH value in this station. The total hardness values are lesser concentrations in the rainy season than in summer. High rate of evaporation increase the concentration of total hardness in the groundwater samples [8].

Carbonate and bicarbonate

The mean values of carbonate are found in the range of 18-48 mg/l and 14-57 mg/l for the groundwater samples in summer and rainy seasons respectively. The mean values of bicarbonates are found to be in the range of 162-511 mg/l and 238-554 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The carbonate values are well within the permissible limit of 200 mg/l (WHO 2011) in all the sampling stations. The bicarbonate values exceed the permissible limit of 150 mg/l (WHO 2011) in all sampling stations in summer and rainy seasons. This may be due to the action of atmospheric CO2 and CO2 released from organic decomposition [9].

Chloride

The mean values of chloride are found in the range of 122-541 mg/l and 85-2472 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The chloride values exceed the permissible limit of 250 mg/l (WHO 2011) at sampling stations S3, S8-S11, S14, S16 and S17 in summer and S1-S4, S8-S12, S14, S16, S17 and S19. High content of chloride in ground water may result from both natural and anthropogenic sources such as run-off containing salts, the use of inorganic fertilizers, landfill leachates, septic tank wastes, animal feeds, industrial effluents, irrigation drainage [10]. Soil porosity and permeability also has a key role in building up the chloride concentration in these stations [11].

Sodium

The mean values of sodium are observed in the range of 67-213 mg/l and 59-525 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The sodium values are within the permissible limit of 250 mg/l (WHO 2011) in most of the sampling stations except at stations S8-S10, S16 and S17 in rainy seasons. High content of sodium in groundwater may be from the release of the soluble products during the weathering of rocks and minerals [12].

Potassium

The mean values of potassium are found in the range of 9-111 mg/l and 7-100 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The values of potassium exceed the permissible limit of 12 mg/l (WHO 2011) in most of the sampling stations except at stations S12, S18 and S20 in summer and S3 and S18 in rainy season. The high value of potassium may be due to the presence of geochemical strata in these stations [13]. Potassium concentration also influenced by the cation exchange mechanism [14].

Calcium and Magnesium

The mean values of calcium and magnesium are found to be in the range of 53-122 mg/l and 20-287 mg/l in summer and rainy seasons and 39-104 mg/l and 31-207 mg/l in summer and rainy seasons respectively (Tables 1 and 2). In the present investigation, the calcium and magnesium values are within the permissible limit of 200 mg/l and 150 mg/l (WHO 2011) in most of the groundwater sampling stations in summer and rainy seasons respectively. High content of calcium and magnesium is recorded in few sampling stations in both summer and rainy seasons. The high calcium content in the ground water can be related to oxidation of organic matter, releasing free calcium in the solution in the acidic pH [15]. The concentration of magnesium also depends upon exchange equilibria and the presence of the ions like sodium.

Nitrate

The mean values of nitrate are found in the range of 18-38 mg/l and 18-123 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The nitrate values exceed the permissible limit of 45 mg/l (WHO 2011) at the sampling stations S9 and S16 in rainy season. The percolation of domestic sewage, industrial wastes, dumping of garbage and leakage of septic tanks enhance the nitrate value [16].

Sulphate

The mean sulphate values are recorded in the range of 39-167 mg/l and 36-242 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The sulphate values are well within the permissible limit of 250 mg/l (WHO 2011) in all sampling stations. The sulphate values are lower in rainy than summer season. This may be due to dilution effect. High level of sulphate imparts a bitter taste to water [17].

Phosphate

The mean values of phosphate are found in the range of 0.23-0.79 mg/l and 0.21-0.69 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The phosphate values exceed the permissible limit of 0.1 mg/l (WHO 2011) in all the sampling stations in summer and rainy seasons. The excess concentration of phosphate may be due to percolation of domestic sewage and agricultural inputs in the study area. During the natural process of weathering, the rocks gradually release the phosphorus as a phosphate ion which are soluble in water and mineralize phosphate compounds breakdown.

Fluoride

The mean values of fluoride are found to be in the range of 0.15-1.70 mg/l and 0.18-1.61 mg/l for the groundwater samples in summer and rainy seasons respectively (Tables 1 and 2). The fluoride values are slightly higher than the permissible of 1.5 mg/l (WHO 2011) in most of the sampling stations. The dissolution of fluoride bearing minerals may be contributing to the high percentage of fluoride in the groundwater samples [18].

Biochemical oxygen demand

The mean values of BOD are found in the range of 20-68 mg/l and 37-86 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The BOD values exceed the permissible limit of 5 mg/l (WHO 2011) in all the groundwater sampling stations in summer and rainy seasons. The high value of BOD may be due to percolation of dumping of domestic wastes, organic wastes, sewage, and industrial wastes [19].

Chemical oxygen demand

The mean COD values are found to be in the range of 26-41 mg/l and 19-45 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The COD values exceed the permissible limit of 10 mg/l (WHO 2011) in all the groundwater sampling stations in summer and rainy seasons. This indicates the pollution by biodegradable and chemically degradable organic matter in the study area [20]. The high value of COD indicates high strength of organic as well as inorganic pollution in the groundwater [21].

Dissolved oxygen

The mean values of DO are found in the range of 2.8-5.3 mg/l and 2.6-5.5 mg/l for the groundwater samples in summer and rainy season respectively (Tables 1 and 2). The DO values are below the permissible limit of 6.0 mg/l (WHO 2011) in most of the sampling stations. The dumping of garbage and the seepage of the landfill may cause the depletion of dissolved oxygen in the groundwater. The DO values are lower in summer than rainy seasons in most of the sampling stations. This may be due to high temperature, percolation of sewage and other wastes might be responsible for low values of DO.

Conclusion

The present study provides significant information on the quality of groundwater in and around Dindigul town. The groundwater is most important for water supply in urban as well as rural areas in developing countries. The results of physicochemical analysis reveal that the parameters such as EC, TDS, HCO3, Cl, K, PO4, BOD, COD and DO exceed the permissible limit of WHO in most of the sampling stations in summer and rainy seasons. The high value of these parameters can be attributed by anthropogenic activities, effective ion leaching and discharge of effluents from agricultural and domestic wastes in summer and rainy seasons. The groundwater in this region can be used for domestic use only after pre-treatment. It is also suggested to monitor the groundwater quality and assess periodically to prevent further contamination.

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