Effects of feeding methods of carbon sources on the water treatment of suspended growth reactors in a recirculating aquaculture system

A suspended growth reactor under continuous carbon resource feeding method (SGR-Con) and another under several steps carbon resource feeding method (SGR-Sev) were operated in a pilot-scale recirculating aquaculture system to compare their water treatment efficiency. It indicated that the concentrations of dissolved organic carbon in the reaction zone of SGR-Con was at a high and stable level, while that in SGR-Sev firstly increased to the same level of SGR-Con during the 0 h in cycle to the instantaneously carbon feeding time and it subsequently decreased to a lower and stable level after 4 h in cycle. Dissolved oxygen in the reaction zone of SGR-Sev, as well as the settling zone was significantly higher than that in SGR-Con. The pH in the reaction zone between different reactors had no significant difference, and it was same in settling zone. Several steps carbon resource feeding method significantly increased the nitrogen removal of reactor. Overall the experimental period, the removal rate of nitrate and total nitrogen in SGR-Sev could be 63.91%±14.31% and 64.07%±12.11%, respectively. Besides, alkalinity in the effluent of SGR-Sev was (278.18±80.33) mg/L. SGR-Sev was favorable to achieve good settling performance of bio-flocs. However, the concentrations of total ammonia nitrogen and nitrite in the effluent of SGR-Sev were higher than those of SGR-Con. In summary, it is better to adopt the several steps carbon resource feeding method for suspended growth reactors.