Water Purification Capacity Of Recirculating Aquaponic System

Aquaponic system is a kind of newly developed food production method that integrates recirculating aquaculture system with hydroponics,the prospect of aquaponic system's future application is brillant because of it's high production efficiency,low pollution emmision and sustainability.In aquaponic system,purification of solvable pollutants and controlling of water quality is crucial to fish and plant production,neverthless,few studies on the purification capacity of aquaponic system have been reported,restricting it's further development.In this study,recirculating aquaponic system was built in the experimental greenhouse of Shanghai Jiao Tong University and operated for more than 180 days.During the recirculating operation period,water quality in each unit was monitored continuously,fish and plant production was measured periodically.In static test,pollutants loads caused by fish feed in recirculating aquaculture units were measured,purification capacity of hydroponic units and immobilized units were invertigated.The results indicated that:?1?In recirculating operation period,water temperature and pH value varied within the suitable growth range of fish and plant,dissolved oxygen stayed at high level,the main nitrogen pollution is NO₃^--N,average concentration of TAN and NO₂^--N were below 1 mg/L;?2?Biomass of fish and plant increased significantly although efficiency of fish production can still be improved,Media filled unit achieved higher plant production than Nutrient film technique unit;?3?Fish feed is the main source of TAN,NO₂^--N,NO₃^--N,DTP and TOC in recirculating aquaculture water,pollutants load caused by each feed in oenanthe rivularis dunn planting period were TAN 900mg,NO₂^--N470mg,NO₃^--N 180 mg,TN 1160 mg,DTP 3800 mg,TOC 3940 mg,and those in spinach planting period were TAN 980 mg,NO₂^--N 610 mg,NO₃^--N 410 mg,TN 2580 mg,DTP 2610 mg,TOC 4650 mg;?4?Two kind of hydroponic units expressed higher removal speed of NO₃^--N than TAN and NO₂^--N,higher removal speed and 24 h removal efficiency of TN than TP,media filled unit achieved high removal efficiency of all pollutants than nutrient film technoloque;Removal efficiency of TAN and NO₂^--N in immobilized nitrobacteria unit were higher than those in Fibre biofilter unit,removal speed in oenanthe rivularis dunn planting period were basically equal to those in spinach planting period,Fibre biofilter unit expressed higher removal efficiency of TOC,removal speed in spinach planting period were higher than thosein oenanthe rivularis dunn planting period.?5?In aquaponic system,removal of TAN and NO₂^--N were achieved mainly by immobilized nitrobacteria unit and partially by hydroponic units,purification capacity were stable in recirculating operation period,average concentration of TAN and NO₂^--N stayed low level;removal of NO₃^--N,TN and DTP were achieved by hydroponic units,purification capacity were influenced by plant harvest,average concentration of NO₃^--N,TN and DTP accumulated continuously to relatively high level;removal of TOC were achieved by immobilized nitrobacteria unit,purification capacity were enhanced along with the biofilm growth,concentration of TOC accumulated continuously in oenanthe rivularis dunn planting period and stayed stable in spinach planting period.