Commercial shrimp farming poses a threat to coastal ecosystem by discharging huge amount of organic and nutrient loads beyond its self-cleansing capacity. Clustering of farms, overstocking of shrimp and consequent high inputs of feed during shrimp culture resulted degradation of the adjoining environment and caused huge mortality of cultured shrimp due to disease outbreak. In an effort to reduce the potential negative impacts in terms of nutrient and organic load in shrimp culture and making shrimp farming sustainable, modified effluent treatment system (ETS) was used to evaluate its efficacy in a semi-intensive shrimp farm of West Bengal, India. ETS was composed of two types of ponds: (i) sedimentation pond, and (ii) bio-filtration pond, and was placed beyond the culture pond outlet. After 120 days of culture it was found that the concentration of different potential nutrients and organic load parameters (ammonia, nitrite, nitrate, phosphate, 5-days biochemical oxygen demand, total suspended solid, Chlorophyll a) were increased substantially in the effluents at pond outlet, and decreased after ETS treatment for 6 days before final disposal. The results substantiated the efficacy of ETS as one of the effective propositions in minimizing environmental pollution, maintaining ecological sustainability and avoiding self pollution in commercial shrimp farms.
Keywords: Effluent treatment system; Nutrient load; Organic load; Semi-intensive; Shrimp culture.