Keywords
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| Water pollution, Distillery effluent, Vembanad Lake. |
INTRODUCTION
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| Water pollution is a very serious hazard caused mainly by sewage and industrial waste discharged into water bodies. The inland waters such as lakes are being deteriorated by increased industrialization due to the addition of used water having chemical constituents of undesirable concentrations. Distillery effluent (spent wash) resulting from sugarcane molasses based industries is one of the most polluting industrial effluents. According to the report of All India Distillers’ Association (AIDA) in India there are 325 distilleries, and in Kerala there are 9 distilleries producing spirit from the molasses. Mc Dowell & Company’s distillery unit at Varanadu in Kerala is situated near the banks of Vembanad Lake. Vembanad Lake extends from Cochin to Alappuzha for a distance of 83 km and is the largest estuary in Kerala. Its width varies from a few hundred meters to 15 km. It is elongated and oriented in NW-SE direction. (Soman, 2002). This estuarine system, the largest of its kind on the west coast is uniquely endowed with all attributes of a tropical wetland, viz. mangroves, waterfowl habitats, agriculture and fisheries. On considerations of these unique endowments, the Vembanad wetlands have been declared recently as a ‘Ramsar site’ for conservation and management. Agriculture and fisheries have been the two most important attributes of these wetlands. During the last century, the Vembanad system has been subjected to a series of human interventions. It was also reported by Kerala State Pollution Control Board (KSPCB) that the Vembanad Lake is polluted by the effluent discharged from Mc Dowell’s distillery unit, the beverage alcohol company in Varanadu, Cherthala Taluk, Alappuzha District (Abraham, 2005). The water produced in an industry, especially distillery, carry a high organic load and cause severe fouling of the atmosphere. This wastewater when discharged to a lake causes severe depletion of oxygen content of the water body. As per the instructions by KSPCB, a new treatment plant was installed in the Mc Dowell & Company during 2004 for the treatment of wastewater from the distillery and it started to function properly from July 2005. This study attempts to understand the physico-chemical characteristics of effluent discharged from the distillery unit and to assess the impact of discharged effluent on the Vembanad Lake in Varanadu area. |
Materials and Methods
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Study area and sampling sites
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| The distillery unit of Mc Dowell & Company is located about 1 km north from Varanadu junction, which is 2 km east of Cherthala bus station in Alappuzha District, Kerala. The study area and sampling sites were shown in Fig 1. The distillery is situated near the banks of the Vembanad Lake. The area of distillery unit is about 2-3 acres. The effluent (spent wash) produced in the distillery during the manufacture of alcohol from molasses is subjected to primary and to a series of secondary treatment processes like anaerobic digestion, aerobic digestion, bio-tower treatment, chemical precipitation, different settling processes such as parallel plate separation, Hopper Bottom settling, and then sand filtration process. After filtration process, the effluent is five times diluted with lake water and then discharged into the lake. |
| Systematic surface water sampling from the Vembanad Lake was done in post monsoon and pre-monsoon seasons during November 2005 – April 2006 period. Water samples were collected from six selected sites (S1-S6) in the lake near the industrial area. Site 1 was 5 m southward from the effluent discharge point. This site is the point where a canal joins the lake. Site 2 is the distillery effluent discharge point, where the effluent mixes with the lake water. Site 3 is about 3 km northward from the discharge point. Sites 4, 5 and 6 are located at the middle portion of the lake, and are 3 km eastward from the sites 3, 2 and 1 respectively. Depth of water in the lake at each location was also measured. Samples of raw (untreated) distillery effluent and treated effluent were also collected. The temperature, colour, odour and pH of the samples were recorded at the time of sampling. All the samples were collected in labeled plastic bottles and transported to the laboratory for the analysis of various physico-chemical parameters. |
| The physico-chemical parameters like temperature, pH, electrical conductivity (EC), dissolved oxygen(DO), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), hydrogen sulphide, total solids (TS), total suspended solids (TSS), total dissolved solids(TDS), total hardness (TH), nitrates, phosphates, sulphates, chlorides, oil and grease, salinity, sodium and potassium were analyzed following the standard methods described in APHA (1995) and by Trivedi & Goel (1986). The chemicals used for the analyses were of analytical grade. |
RESULTS AND DISCUSSION
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| The physico-chemical characteristics of the treated and untreated effluent were given in Table 1. From the analysis, it was found that the raw effluent was having a dark brown colour, sweet odour, high temperature and also high values of total solids, chlorides, sulphates, nutrients, hydrogen sulphide, oil and grease. The pH of the raw effluent was acidic. The BOD and COD values were also high, and the ratio of BOD to COD was found to be 0.528. |
| The suspended solids and colloidal solids in the effluent contribute high BOD and COD. The dissolved oxygen content of the raw effluent was below detectable limit. The values obtained for sodium and potassium were also high in the raw effluent. |
| The treated effluent showed brown colour and with objectionable odour. There was a significant reduction in physico-chemical parameters like temperature, total solids, BOD, COD, sulphates, chlorides, nutrients, oil and grease while the pH value and dissolved oxygen content was slightly increased after treatment. The parameters like pH, BOD and nutrients in the treated effluent were found to be within the standard values for the discharge of effluents to inland surface waters according to CPCB criteria (1993). There was about 99% reduction in BOD load and 98% reduction in the nutrient content of treated effluent compared to that of the raw effluent. But the treatment procedures done by the distillery authorities could not bring the parameters such as total solids, total dissolved solids, TSS, COD, hydrogen sulphide, chloride, oil and grease within standard limits for industrial effluent discharge. Studies by Haniffa and Sundaravandanam (1984) showed that suspended solids present in the effluent disturb the osmo-regulation of fishes and resulted in suffocation even in the presence of adequate dissolved oxygen. The sodium content in the treated effluent was found to be high compared to that of the raw effluent. This may be due to the use of lake water with high sodium content for dilution of the treated effluent before discharge to the water body. |
| The results of the analysis of lake water samples from different sampling sites during pre-monsoon and post monsoon seasons were given in table 2 and 3 respectively. Average depth of the lake in the study area is 2.68m. Lake water samples collected from site 1 and 2 showed a light brown colour and had objectionable odour. While water samples from other four sites, S3, S4, S5 and S6 were having unobjectionable colour and odour. At site 1, 2 and 3, there are maximum changes in the values of different parameters. Mean values obtained for different parameters like temperature, pH, total solid content, total dissolved solids, nutrient content, BOD and potassium in the lake water samples from different sites collected during post monsoon and pre-monsoon seasons were almost similar to that of discharged effluent. While the concentration of dissolved oxygen and hydrogen sulphide was found to be high in lake water samples. The distillery effluent discharged into the stagnant water in the lake get decomposed anaerobically by the action of micro-organisms, which may result in the production of several noxious compounds and gases like amines, hydrogen sulphide etc. Mean COD value was low in lake water samples studied compared to the treated effluent, but above the permissible limit for natural water quality standards. Oil and grease were found to be high in lake water samples in pre-monsoon season compared to that of the treated effluent. While in post monsoon period, it was found to be low in the lake water samples. The presence of high amount of total solids, hydrogen sulphide, oil and grease etc. degrade the quality of Vembanad lake water and are detrimental to the aquatic life, including fishes. Studies by Verma et al. (1979) also showed that the effluent stagnation in the stream may lead to the production of obnoxious compounds and gases which are detrimental to aquatic organisms living therein. The mean nutrient content of lake water samples in pre-monsoon and post monsoon seasons were within standard permissible limits for natural waters. The mean value for salinity in lake water samples was found to be high in the pre-monsoon season compared to that of post monsoon season. Salinity in estuaries determines its environmental character, occurrence and abundance of organisms. |
| Thus on the basis of the present study, it was concluded that due to the treatment of raw effluent in the treatment plant of the Mc Dowell and Company distillery unit, there is a considerable reduction in the pollution potential of Vembanad Lake receiving distillery effluent in Varanadu area. Now the pollution load in the lake with respect to distillery effluent is decreased compared to the previous reports by Kerala State Pollution Control Board and Abraham (2005). The primary and secondary treatment processes were found to be efficient in reducing the major pollutants in the distillery effluent such as temperature, BOD, COD, nutrients, oil and grease, and total solid content to a considerable extent, but the treatment process followed in the distillery unit could not reduce the concentration of sodium, potassium, oil and grease, total solids, total dissolved solids, hydrogen sulphide, dissolved oxygen and BOD & COD values upto the standard limits for the discharge of effluents into inland surface water as prescribed by CPCB criteria (1993). Thus certain modifications have to be done in the treatment processes for enhancing the efficiency of the treatment plant so that the pollutant level can be further reduced to attain the standard limits for effluent discharge to inland surface waters. |
RECOMMENDATIONS
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| The following effective methods should be implemented for enhancing the efficiency of the treatment plant: |
| a. Activated carbon can be used for removing soluble organics, colour and odour producing substances. |
| b. Ion exchange method can be used to remove hardness causing ions like Ca, Mg and manganese salts from wastewater. |
| c. Oil and grease present in the effluent should be removed by using techniques like dissolved- air flotation. |
| d. Aeration should be done properly to remove gases like hydrogen sulphide and CO2. |
| e. Implementation of reverse osmosis plant can optimize the level of TDS in the effluent. |
ACKNOWLEDGEMENT
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| The authors thank Dr.V.Sobha, Professor and Head, Department of Environmental Sciences, University of Kerala for providing the laboratory facilities required to carry out the present study. |
Tables at a glance
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Figures at a glance
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| Figure 1 |
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References
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- Abraham, V. 2005. Environmental pollution causes high incidence of cancer in three Kerala villages on Vembanad Lake. The Week (10th April).
- APHA. 1995. Standard Methods for the Examination of Water and Waste Water, 19th Edn, American Public Health Association, Washington DC.
- CPCB. 1993. Environmental Standards. 32. General standards for discharge of environmental pollutants, Part A. Ministry of Environment and Forest (MoEF), Government of India.
- Haniffa, M.A. and Sundaravandanam, S. 1983. Effect of distillery effluent on food utilization of freshwater fish Barbus Stigma. Life Sci. Adv. 2:142 - 146.
- Soman, K. 2002. Geology of Kerala. Geological Society of India, Bangalore, p.336.
- Trivedy, R.K. and Goel, P.K. 1986. Chemical and Biochemical Methods for Water Pollution Studies. Environmental Publications, Karad, India. p. 247.
- Verma, S.R., Tyagi, A.K., Kumar, K. and Dalela, R.C. 1979. Characteristics and Disposal of distillery wastes. In: Environmental Biology. (Eds. S.R. Verma, A.K.Tyagi and S.K.Bansal) The Academy of Environmental Biology, Muzaffarnagar.p. 281– 301.
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