Effects of Fe2+, Mn2+, SO42− on nitrogen removal in an Anammox biofilter

Nitrogen pollution was the main cause of black-odorous water, while Fe2+, Mn2+, and SO42− also contributed to that. In this study, the effect of Fe2+, Mn2+, and SO42− on the nitrogen removal of Anammox process was investigated, and its feasibility for the remediation of black-odorous sediments was analyzed. Results showed that the Fe2+ and Mn2+ at 1 mg L−1 and SO42− at 100 mg L−1 had positive impact on the anaerobic ammonia-oxidizing bacteria (AAOB) activity and the total nitrogen removal efficiency (TNRE) averagely increased from 78.5% to 79.4%. However, the Fe2+ and Mn2+ at 3–20 mg L−1, and SO42− at 100–800 mg L−1 resulted in a gradual decrease in TNRE, and finally decreased it to 43.9%. When the Fe2+ and Mn2+ increased from 20 to 50 mg L−1, and the SO42− increased from 1600 to 2000 mg L−1, the TNRE returned to 76.6% due to the adaption of the Anammox bacteria. Once the addition of Fe2+, Mn2+, and SO42− was stopped, the TNRE significantly recovered to 85.7%. The relative abundance of Candidatus Kuenenia increased up to 71.8% when Fe2+, Mn2+, and SO42− was 1, 1, 100 mg L−1, and decreased down to 26.7% in the inhibition phase when Fe2+, Mn2+, and SO42− was 20, 20, 800 mg L−1, respectively. Overall, the Fe2+, Mn2+, and SO42− in low concentrations has a promotion effect on the nitrogen removal of Anammox system, and indicating that it has good application prospect for restoring black-odorous water.