Development and application of a three-loop recirculating freshwater aquaculture system
In order to meet the increasing demand for high-quality fish protein and environmental protection requirements,a pilot intensive three-loop recirculating freshwater aquaculture system(RAS)was developed in Qionghai,Hainan province,China.Backwashing water from a microfilter is used as the carbon source for the denitrification process,and an operation mode is established to ensure the treatment of water quality and fish sludge to comply with the requirements for fish growth and pollution control.Tilapia(Oreochromis mossambicus)was cultured in the pilot three-loop freshwater RAS for 121 days in an aquaculture experiment,and the fish growth,water quality and microbial communities in the system were observed and analyzed.The results showed that the tilapia had a survival rate of 100%,with the stocking density and the feed conversion ratio(FCR)being 107.7 kg·m-3 and 1.74,respectively.The average concentrations of total ammonia(TAN),nitrite(NO2--N)and nitrate(NO3--N)were 0.95,0.15 and 43.01 mg·L-1 respectively.The volume for daily water drainage was 2.66%of the total water volume in the system,and 6.67%of the water volume in the fish tank.No fish sludge was discharged throughout the experiment,and only a small amount of sludge existed in the anaerobic digestion unit by the end of the experiment.Microbial community analysis showed that a total of 21 genera of microorganism were involved in nitrogen metabolism,including Rhodobacte,Flavobacterium and Azospira.These results implicated that the recirculating aquaculture system provides a potentially sustainable and ecological aquaculture mode for freshwater fish such as tilapia.
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维普
