Denitrification of wastewater with external carbon source of solid wastes in recirculating marine culture system

In recirculating aquaculture system, wastewater characterizes as low C/N ratio and high dissolved oxygen (DO) content, deoxygenating and adding extra organic carbon are necessary for complete denitrification of wastewater. Solid wastes were utilized as extra organic carbon source in the anaerobic hydrolysis and denitrification of wastewater in recirculating marine culture system. After hydrolysis for 10 hours of the wastewater (with volumetric ratio of hydrolytic sludge to solid wastes of 1:1 and at 20℃), the concentrations of NH4+-N, NO3--N, total chemical oxygen demand (TCOD) and total solid (TS) decreased 62.8%, 43.5%, 24.0% and 13.6%, repectivelly, and DO concentration dropped to 0.2 mg/L. When wastewater, which the volumetric ratio of hydrolytic sludge to solid wastes was kept within 1:1.5-1:2.5, hydrolyzed at 20℃ for 6 hours, volatile fatty acid (VFA) concentration and SCOD/TCOD ratio (dissolved organic substance / total organic substance) would increase 32.0%-49.3% and 3.5%-9.1%, respectively. Denitrification of hydrolytic wastewater (with volumetric ratio of anaerobic denitrifying sludge to hydrolytic wastewater of 1:4) could completely carried out at 20℃. The consequent removal rate of NO3--N and TCOD in 3 hours reached to 99.6% and 88.3%, respectively. Whereas 36.5% and 75.9% of removal rate for NO3--N and TCOD in 10 hours were observed in direct denitrification of marine culture wastewater. It is demonstrated that in recirculating marine culture system complete denitrification is possible by a combining hydrolysis of solid wastes and wastewater.