Nitrogen removal performance of high ammonium and high salt wastewater by adding carbon source from food waste fermentation with different acidogenic metabolic pathways.

Food waste fermentation liquid components, mainly lactate and volatile fatty acids (VFAs), can be used as alternative carbon sources to improve the nitrogen removal efficiency. To investigate the effects of carbon sources generated from food waste (FW) fermentation liquid on nitrogen removal for the treatment of high ammonium and high salt wastewater (HAHS), the lactate, acetate, propionate, butyrate, and their mixtures were added in activated sludge systems operating over 130-days. Lactate and butyrate inhibited nitrifiers by enriching polyphosphate accumulating organisms (PAOs), thus deteriorated nitrogen removal after a long-term period. When fed with acetate or propionate, the dominant glycogen accumulating organisms (GAOs) groups simultaneously realized nitrification and denitrification. The mixed carbon source enhanced microbial community robustness and the transformation of Polyhydroxyalkanoate (PHA), advancing nitrogen removal efficiency. Mixed carbon source of acetate-propionate was preferred, in which the coexisting groups of GAOs and PAOs enhanced the denitrification rate of denitrifiers and kept balancing with nitrifiers, where the highest denitrification rate (DNR) was 1.05 mg N/(h·g VSS) and the average TN removal efficiency was above 98% under the maximum nitrogen load of 0.48 kg N/(kg VSS·d). In addition, the primary pathways of nitrogen removal were heterotrophic nitrification and denitrification, since the autotrophic nitrifiers were inhibited by the free ammonium and salinity. This study illustrated the differences of nitrogen removal performance and mechanisms with fermentation liquid components as carbon sources processing of HAHS wastewater.