Thermophilic bacteria combined with alkyl polyglucose pretreated mariculture solid wastes using as denitrification carbon source for marine recirculating aquaculture wastewater treatment

Highlights: • TB + APG could synergistically enhance the hydrolysis and acidification of MSW. • MSW acidogenic liquid was the reliable carbon source for denitrification. • The optimum C/N was 8 with no residual of NO_x⁻-N. • VFAs was the optimal carbon source in MSW acidogenic liquid. • The obvious superiority of optimum C/N was obtained by kinetics analysis. In marine recirculating aquaculture systems (RAS), efficient nitrogen removal is challenging due to the high NO₃⁻-N concentration, low organic matters content, and high salinity. In this study, mariculture solid wastes (MSW) acidogenic liquid pretreated by thermophilic bacteria (TB) combined with alkyl polyglucose (APG) was first used as carbon source for denitrification to remove NO₃⁻-N. TB + APG pretreatment could accelerate the hydrolysis of MSW, and the highest volatile fatty acids (VFAs) yield (40.3%) was obtained with TB + 0.2 g/g VSS APG pretreatment. MSW acidogenic liquid pretreated by TB + 0.2 g/g VSS APG was a reliable carbon source for denitrification, and the optimum COD/NO₃⁻-N ratio (C/N) was 8 with no residue of NO_x⁻-N. VFAs were more effectively utilized by denitrifiers than carbohydrate and protein. The high denitrification potential (P_DN) and denitrification rate (V_DN) indicated the higher denitrification ability at C/N of 8 using MSW acidogenic liquid as carbon source. The outcomes of this work could provide useful information for promoting technological innovation in marine RAS wastewater treatment.