Environmental sustainability assessment of Nile tilapia (Oreochromis niloticus) breeding in biofloc system

Sustainable development aquaculture industry entails the expansion of environmentally friendly systems. The aim of this study was to evaluate the environmental aspects of biofloc technology system (BFT) in Nile Tilapia (Oreochromis niloticus) culture. This research was performed on two systems including, Biofloc and flow-through system (FTS). Each system had three replications and carried-out for six months and sampled at intervals of 15 days. The density in each 30m3 pond was 1500 juveniles of Tilapia (25 g b/w each). The studied parameters include fish weight, oxygen, temperature, ammonium, nitrite, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) of effluent, feed conversion ratio (FCR), specific growth rate (SGR), protein efficiency ratio (PER), survival rate, and cost of culture. The results indicated that temperature, oxygen, nitrite, and ammonium were significant different (p<0.05) and lowest level of NO3(0.004mg/L), NH4 (0.002 mg/L) observed in BFT. There were significantly different between growth indices and all physiochemical factors except for pH, during the time. Effluent factors include BOD, COD and TDS in BFT were significantly lower than FTS (p<0.05). The quality of the effluent in BFT contained only 5%of the food with the effluent and 25% of the food reused in the food chain, while in flow-through, 25-30% of food discharged along with FTS. The water exchange rate in BFT was 1.5m3/day(5%/day) and in flow-through was 30m3/day (0.3 L/s). The cost of feeding in BFT was 25% lower than FTS system. Therefore, the results revealed that BFT, in addition to water quality improvement, leads to less feed consumption, higher quality production, and less environmental pollution.