Reutilization of Wastewater from Freshwater Ornamental Fish Farm through Chemical and Biological Processes

Abstract

The possibility of reuse of wastewater from freshwater ornamental fish farm for aquaculture purpose was studied by treating it chemically and biologically. Chemical agents like calcium oxide (quick lime), ferric chloride, ferric aluminum sulphate (ferric alum) and fly ash were used. Highest percentage reduction in ammonia (60.3%), phosphate (59.24%) and chemical oxygen demand (COD) (70.32%) was observed after treatment with quick lime, fly ash and alum respectively. In biological process, micro algae Chlorella vulgaris and duck weed Lemna minor were used. In micro algal treatment, chemically treated wastewater did not show any significant production of algae despite significant difference (p<0.05) among algal growth in different days of algal culture. At the end of culture, highest net photosynthesis and assimilation number obtained from fly ash was 16.36 ± 0.99 and 24.42 g m-3 h-1 respectively. Level of ammonia and phosphate was drastically reduced from 124.52 to 2.61 µg at-N l -1 and 56.52 to 0.168 µg at-P l -1 respectively in the wastewater treated with fly ash and micro algal culture. COD level was reduced from 112.80 to 5.1 mg l -1 after treating the wastewater with ferric chloride and micro algal culture. No production of Lemna was registered from the wastewater treated with lime and ferric chloride. The culture of duck weed drastically reduced the ammonia level from 74.38 to 3.82 µg at-N l -1 and 59.66 to 1.84 µg at-N-1 in alum and fly ash treated wastewater respectively. No trace of phosphate was recorded in the Lemna treated waters. In culture trial of common carp fry, fly ash treated and fly ash cum algal cultured wastewater showed high net growth efficiency. Net growth efficiency varied significantly (p<0.01) between chemically treated and biologically treated waters.