Rapid start-up of simultaneous nitrogen removal and sludge reduction in a single reactor through fermented sludge bioaugmentation

Integrating anammox with fermentation is expected to achieve efficient nitrogen removal and in-situ reduction of excess sludge, which can significantly reduce the cost of mainstream wastewater treatment. In this research, the feasibility of rapid start-up of simultaneous partial nitrification, anammox, denitrification and fermentation (SNADF) process by fermented sludge bioaugmentation was studied. In addition, excess sludge was regularly supplied to the system to explore the sludge treatment potential of the SNADF system. Within 81 days, the SNADF system achieved efficient nitrogen removal (88.17%), coupled with significant sludge reduction capability (Yobs: -0.394 kgMLSS/kgCOD). An in-situ test revealed the synergistic relationship between fermentation and partial denitrification/anammox (PD/A) in the absence of organics, indicating the start-up of SNADF system. Moreover, the continuous decrease in biomass concentration indicated the considerable potential of SNADF in treating the excess sludge. The anaerobic ammonia oxidizing bacteria (AnAOB) were obviously enriched (0.03%-0.25%), ensuring efficient nitrogen removal. The ammonia oxidizing bacteria in excess sludge facilitated AnAOB enrichment, while the excess sludge increased biomass concentration and promoted fermentation. The fermentation process mainly stopped at the acid-producing stage and promoted PD/A process. These results suggest that the SNADF system simultaneously promoted fermentation and nitrogen removal in a single reactor.