Impact of increasing sulfide addition on the nitrogen removal and microbial community of CANON process in membrane bioreactor

Simultaneous removal of nitrogen and sulfur pollutants was an urgent issue since they coexisted in many kinds of wastewater and led to the black-odor water. In this study, sulfide was step-wise increased and added to the completely autotrophic nitrogen removal (CANON) system, to investigate its impact. Results showed that autotrophic denitrification was successfully induced and then improved the total nitrogen removal efficiency (TNRE) to 91.9 % from 83.7 %, when 0-5 mg L-1 sulfide was supplied. However, 50 mg L-1 sulfide significantly decreased TNRE to 42.9 %, together with the decrease of hydroxylamine oxidoreductase activity to 1.05 from 1.77 EU g(-1) SS and Heme-c to 0.15 from 0.28 mu M g(-1) SS. CANON system can resist the sulfide shock after acclimatization, the TNRE slightly decreased to 82.9 % when 50 mg L-1 sulfide was supplied again. Prominent nitrogen removal was achieved in CANON system with 5 mg L-1 sulfide, by the cooperative contribution of CANON bacteria (5.77 % Nitrosomonas, 20.2 % Candidatus Kuenenia) and denitrifying bacteria (7.52 % Truepera, 1.79 % Denitratisoma and 3.72 % Arenimonas).

Automated summary

The simultaneous removal of nitrogen and sulfur pollutants is crucial, with low levels of sulfide enhancing total nitrogen removal efficiency while high levels of sulfide significantly decrease efficiency. After acclimatization, the CANON system can resist sulfide shock and achieve good nitrogen removal efficiency under 5 mg L-1 sulfide concentration. Prominent nitrogen removal is achieved through the cooperative contribution of CANON bacteria and denitrifying bacteria in the system.