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Present communication deals with the sources and physico - chemical characteristics of effluent of Galvanizing Industry. Analysis of effluent revealed acidic pH, high BOD and COD load. The effluent contained number of metallic pollutants comprising Fe, Zn, Pb and Cr.
Galvanizing Industry, Effluent, Sources, Physicochemical characteristics
Pollution of environment by industrial effluent has been a major concern in recent years. The raw materials, variety of chemicals and metals and the technologies used are the primary factors determining the quality of released effluent of an industry. The components of the effluent contributed to the characteristics of the effluent and capable of altering the physical, chemical and biological characteristics of receiving ecosystem. The study of the industry effluent helps to understand quality of effluent and its impact on ecosystem.
Studies on physicochemical characteristics of industrial effluent were carried out by Dhaneswar et al. (1970), Mohanrao and Subrahmanium (1972); Agarwal and Kumar (1978); Choubey et al. (1986); Bhaskaran et al. (1989); Shaw et al. (1990); Sinha (1993); Baruah et al. (1996), Amudha and Mahalingan (1999); Das et al. (2000); Sundarmoorthy et al. (2000) and recently by Kumar et al. (2001). Due to dearth of literature on galvanizing industry, the present investigation was carried out to study the sources and physicochemical characteristics of galvanizing industry effluent.
Sources of effluent
There are two common galvanization methods i.e. Hot dip method and Electrolytic methods. The hot dip method is predominant in utility specially for galvanization of large size materials. During this process the mild steel materials are subjected to series of treatments including initial cleaning by bathing in acids, in water and in alkali followed by baths in molten lead, in ammonium compound ,in molten zinc and finally washed in hot water. Later, the materials are packaged and dispatched to market. The effluent is generated from the bathing, washing and cooling units and is almost regular in flow. The bathing units are emptied for the rejection of liquors as effluent after they assume the limiting concentration of raw materials. The volume of affluent depends upon the nature and quantity of product of galvanization.
The effluent was collected in sterilized plastic container from the outlet of effluent treatment plant of a galvanizing industry located at the periphery of Guwahati city. The samples were brought to laboratory and analysed by following standard methodology of APHA (1985) and Trivedy and Goel (1986). The study was carried out monthly for a period of two years ie.2003 and 2004.
The result of physicochemical analysis is presented in Table 1-2.The pH value indicated extremely acidic nature of effluent due to presence of acids originated primarily from the cleaning units of the industry. The high conductivity value suggested the occurrence of large amount of inorganic compounds in the effluent. The elevated value of turbidity also indicated the presence of sizable amount of suspended solids derived from washing and bathing units of the industry.These observations were in the line of Das et al. (2000) in waste water of open cast mining and Sundarmoorthy et al. (2000) in fertilizer factory effluent.
The analysis of effluent recorded high load of biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The BOD load was associated with the presence of organic materials perhaps in the form of organic waste and the COD load was linked with the oxidisable chemicals in the effluent. Similar findings were reported by Mohanrao and Subrahmanium (1972); Sinha (1993); Baruah et al. (1996); Das et al. (2003), in the effluent of dairy, sugar, paper and oil industry respectively.
The analysis further revealed large amount of iron and zinc and marginal amount of lead and chromium. All these metallic substances originated from the raw materials ,bathing and washing units of the industry. The presence of different metals contributed to the toxicity of the galvanizing industry effluent and to the living organism also. Presence of toxic metals was earlier reported by Shaw et al. (1990); Baruah et al. (1996); Devi et al. (2001) in the effluent of chloro-alkali, paper and galvanizing industry respectively.
From the above findings it can be concluded that the galvanizing industry effluent is toxic in nature, capable of altering the quality of receiving ecosystem and harmful to the living organisms both plants and animals. The effluent requires appropriate treatment to reduce its toxicity to a minimum level before releasing into nearby areas.
The authors are greatful to University Grants Commission for the financial assistance and Principal, B. Borooah College, Guwahati for providing facilities to carry out the investigation