Using sulfide as nitrite oxidizing bacteria inhibitor for the successful coupling of partial nitrification-anammox and sulfur autotrophic denitrification in one reactor

The partial nitrification-anammox (PNA) process, as a new green biological nitrogen removal technology, is completely autotrophic and has great economic and environmental benefits. However, the applied bottleneck of this process is the inability to inhibit nitrite oxidizing bacteria (NOB) activity and the low total nitrogen removal efficiency (TNRE) due to nitrate accumulation. In this study, the addition of sulfide was utilized to selectively screen NOB while promoting the sulfur autotrophic denitrification (SAD) process in one sequencing batch biofilter granular reactor. The results showed that when the influent concentration of NH4+-N and S2- were 184.6 +/- 4.4 mg/L and 153.9 +/- 3.1 mg/L, the average TNRE reached 89.6 +/- 3.6 %. At this stage, aerobic ammonia oxidizing bacteria (AOB) and anaerobic ammonium oxidation bacteria (AnAOB) showed good activities (specific oxygen uptake rate of AOB and specific anammox activity could reach to 0.09 +/- 0.00 mg O2/g SS/h and 0.47 +/- 0.06 mg TN/g SS/h, respectively), while NOB activity was significantly suppressed by sulfide, with specific oxygen uptake rate of 0.003 +/- 0.00 mg O2/g SS/h, which further demonstrating the feasibility and long-term application of this sustainable and efficient process. Anammox was the predominant nitrogen removal pathway contributing approximately 89.0 % of nitrogen removal. Typical AOB (Nitrosomonas), AnAOB (Candidatus Kuenenia), and SAD bacteria (Thiobacillus, Pseudoxanthomonas, and Limobacter) coexisted in the PNA-SAD system. The syntrophic interactions among sulfur-oxidizing, sulfate-reducing, and anammox bacterial populations of this system were revealed by PICRUST2 and network analysis. Sulfides were most likely oxidized to biologically produced elemental sulfur first and then converted to sulfate via the Sox system. Our study provided a new reaction scheme and theoretical reference for efficient nitrogen and sulfur removal in a single reactor.

Automated summary

The partial nitrification-anammox (PNA) process is a new green biological nitrogen removal technology that utilizes sulfide to selectively inhibit nitrite oxidizing bacteria (NOB) activity while promoting sulfur autotrophic denitrification (SAD) process, thereby improving nitrogen removal efficiency and sulfur removal efficiency.