Rapid start-up of simultaneous nitrogen removal and sludge reduction in a single reactor through fermented sludge bioaugmentation
In this research, the possibility 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 operation of the SNADF system resulted in an efficient nitrogen removal (88.17%), coupled with significant sludge reduction capability (-0.394 kgMLSS/kgCOD). An in-situ test revealed the synergistic relationship between fermentation and partial denitrification/anammox (PD/A) in the absence of organic, 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.