C.M. Noorjahan, S. Dawood Sharief and Nausheen Dawood
School of Environmental Science P.G. and Research Department of Zoology The New college, Chennai- 600 014, India.
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Physico-chemical parameters of both untreated and industry treated dairy effluent was carried out. The results revealed that BOD, COD, TDS, TSS etc. of dairy effluent were found to be high even after treatment exceeding the CPCB limits
Dairy waste, waste characterization, water pollution control.
Industrialisation is an important tool for the development of any Nation. Consequently the industrial activity has expanded so much all over the world today, that it has become a matter of major concern of the deteriorating environment (Tiwari, 1994). With the rapid growth of industries in the country, pollution of natural water by industrial waste has increased tremendously (Muthusamy and Jayabalan, 2001). Water pollution is the most serious problem faced by Man today. Dairy industry is one of the important industry causing water pollution. In India, dairy industry generates about 6-10 litres of waste water per litre of milk processed depending upon the process employed and product manufactured (Tiwana, 1985).
Generally dairy wastes contain large quantities of milk constituents such as casein, lactose, fat, inorganic salts besides detergents and sanitizers which contribute largely towards high BOD and COD (Marwaha et.al., 2001). The high values of suspended solids and dissolved solids shows its high pollution potential. Discharge of such wastes into inland surface water will lead to depletion of oxygen in the water bodies, affecting aquatic life and creating unaesthetic anaerobic conditions.
Several investigations and their reports are available about other industrial effluents, but work on dairy effluent is meagre. Hence the present investigation is aimed to analyze the physico-chemical characteristics of the both untreated and industry treated dairy effluent.
For the present study, dairy effluent (Both untreated- site A and industry treated- site B) were collected from a dairy, situated in Chennai.
Effluent was collected in 2 1/2 litres capacity polythene containers for a period of 18 months from January 2001 to June 2002 and were brought to the laboratory with due care and were stored at 200C for further analysis. The physico-chemical parameters such as pH, EC, TDS, TSS, BOD, COD, alkalinity, total hardness, oil and grease, sodium, potassium, calcium, nitrate , sulphate, a phosphate and chloride of dairy effluent were analyzed following Standard procedure of APHA (1989).
Analysis of physico-chemical characteristics of the dairy effluent collected from site A and B for a period of 18 months are shown in Table 1 and 2. The present investigation revealed that the dairy effluent was milky and greyish black in colour with disagreeable odour which may be due to decomposition of organic matter or presence of various aromatic and volatile organic compounds (Singh et.al., 1998) and it may also be due to microbial activity (Nagarajan and Shasikumar, 2002). A large number of pollutants can impart colour, taste and odour to the receiving water there by making them unaesthetic and unfit for domestic consumption. The pH of untreated dairy effluent was between 4.5 to 9 and while in industry treated efflunet it ranged from 7.0 to 8.5. Though the pH is alkaline in fresh conditions, the waste becomes acidic due to decomposition of lactose into lactic acid under anaerobic conditions and may cause corrosion of sewers (Joseph, 1995).
The electrical conductivity (EC) of untreated dairy effluent ranged between 1075-2886 μhos/cm whereas in industry treated effluent it was between 885 to 1950 μhos/cm and they were found to be within the permissible limits (3000 μhos/cm) issued by irrigation guidelines (Hamoda and Al- Awadi, 1996). Such low EC could be attributed to the presence of organic compounds in the effluent (Marwaha et.al., 1998).
TSS levels in both untreated (20-700 mg/L) and industry treated (19-650 mg/L) were found to be beyond the permissible limit (100 mg/L) of ISI (1979) for effluent discharge which could be due to various environmental factors, reducing the diversity of aquatic life and resulting in oxygen depletion.
With regard to TDS, both untreated and industry treated effluent were found to have high levels of TDS compared to permissible limits of CPCB (1995) and this high level of TDS may be due to salt content present in the sample and also renders it unsuitable for irrigation.
The results of present study revealed that BOD levels of both untreated (260-490 mg/L) and industry treated (100-250 mg/L) dairy effluent surpassed the CPCB limit of 30 mg/L for effluent discharge into inland surface waters reflecting high organic load and pollution potential. Moreover the presence of organic matter will promote anaerobic processes leading to the accumulation of toxic compounds in water bodies. This is in accordance with the work of Panneerselvam (1998) and Prabakar (1999).
The present investigation showed high levels of COD in both untreated and industry treated effluent which could render the aquatic body unsuitable for the existence of aquatic organism (Goel, 2000) due to the reduction in the dissolved oxygen content (Panneerselvam, 1998).
Analysis of dairy effluent from both sites showed the presence of oil and grease which was far below the permissible limits of CPCB (1995). Though oil and grease are found in negligible amount, its continuous discharge into an aquatic ecosystem could also destroy the nursery ground of a variety of fishes (Kumaraguru, 1995). Alkalinity was found to be high which is harmful to aquatic organism (Nemerow, 1978).
It may be noted that total hardness, calcium, potassium, sodium, nitrate, sulphate and phosphate including chloride were found to be higher in both the untreated and industry treated dairy effluent when compared to the limit prescribed by IKC (1993) and CPCB (1995). The presence of ions impart hardness to water and make it unsuitable for washing, bathing and industrial purposes. The results of the above study is in agreement with the work of Panneerselvam (1998) and Prabakar (1999) in sago and sugar mill effluents. From the results of above study it can be inferred that physico-chemical parameters such as BOD, COD, TDS and TSS were recorded to be higher than the permissible limits of CPCB in both untreated and industry treated dairy effluent. Moreover, the untreated effluent was found to be more toxic compared to industry treated effluent which may be due to the treatment process that perhaps reduced the toxicity of the effluent and this is in accordance with the observations of Thorat and Wagh (2000), Noorjahan et. al. (2000) and Nagarajan (2002) and Shasikumar (2002). Though a number of physical and chemical methods are available for the treatment of dairy effluent one such method which gained importance is the biological method using micro organism and it was found to be most promising technique for the dairy waste treatment (Chaubey, 2002) and the micro organisms serves as efficient detoxifiers of pollutants capable of oxidizing the organic and inorganic constituents. Further the biologically treated dairy effluent can be used for agricultural (Geetha and Vembu, 1998) and aquacultural purposes (Nagarajan and Shasikumar, 2002) after suitable dilution.