Detailed physico-chemical studies on abattoir effluent using lime, alum, ferrous sulphate and an anionic polyelectrolyte were tried individually and in combination. Among the coagulants tried, lime resulted in good settling of the sludge. At 400 mg l(-1) of lime dose, the Suspended Solids (SS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) removals were found to be 41.9%, 38.9% and 36.1%, respectively. Best results were obtained with lime and ferrous sulphate in a combination ratio of 400:100 mg l(-1), and the COD reduction of 36.1% at 400 mg l(-1) of lime, further improved to 56.8%. Lime and alum dose of 400:50 mg l(-1) resulted in an increased COD reduction of 42.6% compared to 36.1% at lime dose of 400 mg l(-1). However, the same lime dose with ferrous sulphate addition of 100 mg l(-1) resulted in an increased COD reduction of 56.8% compared to 36.1%. This is a more efficient option for abattoir wastewater treatment and also cost effective. Ferrous sulphate with anionic polyelectrolyte resulted in good removals. Though it is a costly chemical, the dose needed is just half that of lime and just 0.1 mg l(-1) of anionic polyelectrolyte resulted in good reductions in SS, BOD and COD of 54.2%, 49.6% and 43.8% respectively. Studies indicated that the lime and ferrous sulphate in the combination of 400:100 mg l(-1), and ferrous sulphate and polyelectrolyte in the combination of 100:0.1 mg l(-1) are the two feasible options. Lime in combination with alum can also be applied but resultant sludge volume would be more.
Bioaccumulation kinetics and bioconcentration factor (BCF) of chlorinated pesticides like Aldrin, Dieldrin, Benzene hexachloride (BHC), and Dichlorodiphenyl-dichloro-ethane (DDT) in fish tissues of Puntius ticto was studied in detail in a continuous fed system. The bioconcentration process is summarized by using a first order uptake model and the steady-state BCF is calculated based on the 30 days exposure. Rate of bioaccumulation of DDT was maximum of 4.6432 microg g(-1) wet weight per day in liver tissue whereas it was minimum of 0.0002 microg g(-1) wet weight per day in case of Dieldrin in the muscle tissue among the pesticides. It was observed that DDT showed maximum BCF of 89.010 in case of liver tissue of the fish exposed to 30 days. The regression coefficient (r2) between pesticide concentration and exposure time varied between 0.6212 and 0.9817 indicating high correlation. Based on actual calculated BCF values, the octanol water partition coefficient (Kow) values were predicted. In order to prove the hydrophobic property of chlorinated compounds and its affinity towards lipid, the Kow is predicted. Results showed that pesticide burden differ from tissue to tissue and can be correlated to the lipid content, size, exposure time, and species.
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