THE FATE OF IIEAVY METALS IN AQUACULTURE SEWAGE TREATMENT' PLANT (ASTP)BIBHUDATTA MISHRA, S. AYYAPPAN AND SWOYAM P. ROUTAbstract The distribu Lion ot hea vv incLi Is was stud led through out the process of treatment in a 1 MLD Aquaculture Sewage Treatment Hant (ASTI') based on duckweed and fish culture. Duckweed is a small floating plant having the ability to absorb heavy metals. In the present study, concentrations of dissolved free iron, copper, manganese, zinc and lead in influent were analysed through various stages of treatment. Observations reveal that considerable amount of reduction in heavy metals was affected within two days retention period in 18 nos. duckweed ponds (25m X 8m X 1.5m) and three days retention in 2 nos. fish pond (50m X 20rn X 2m) respectively. The mean percentage reduction was observed 72.04 WO, 80.55% (Cu), 90.38% (Zn), 92.89% (Mn) and 81.82 % (Pb) within the treatment complex. The removal rate of duckweed showed 1.03 g/rn:/d for iron, 0.072 g/m2/d for copper, 0.49 g/m=/d for manganese, 0.55 g/m2/ci for zinc and 0.038 g/m2/d for lead respectively. Similarly the reduction levels recorded in fish pond ensures that the fishes are safe for human consumption. None of the five heavy metals tested appeared to have any significant effects on the biomass harvest (duckweed/ fish) and treatment efficiency of the ASTP system. The newlye biological system demonstrates a low cost technology for heavy metal removal with production of treated sewage and design cost technology for heavy metal removal with production of treated sewage and safe fish yield.
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