Dual Purpose of Domestic Waste-Water Reuse: Fish Production and Eutrophication abatement

Abstract

Recycling waste water is an alternative to the gradual degradation of natural water resources. In the present study, domestic sewage effluent was used for the removal of nutrients via poly fish culture. Carps were stocked in primary and secondary oxidation ponds and their growth rate was measured every 3 months for a period of one year and was compared with freshwater control pond. Major nutrients present in the sewage secondary oxidation ponds were found to be significantly removed and utilized by the fishes grown in these ponds. The fish growth rate in one year was as follows: C. carpio 1780 gms, L. rohita 1300 gms and C. mrigala 1100 gms. These were 3 to 4 times higher than the same species of fishes grown in freshwater control pond. It is concluded that the fishes grew very fast in the secondary oxidation ponds without any supplementary feeding, attenuating the eutrophication of water by consuming the excessive amount of nutrients via the natural food chain, which was available in plenty in the tropical ponds.  It was also found that the concentration of nitrogen and phosphorus was much higher in oxidation ponds, where there was no fish culture.