Effective recovery of the nitritation process through hydrogen peroxide.

This study successfully achieved stable nitritation by adding hydrogen peroxide (HO) to the nitrification sludge whose nitritation stability had been destroyed. The batch experiment demonstrated that, the activity of ammonia-oxidizing bacteria (AOB) was restored more rapidly than that of nitrite oxidizing bacteria (NOB) after the addition of HO, thereby selectively promoting AOB enrichment and NOB washout. When the HO concentration was 6.25 mg/L, the NOB activity was significantly reduced and the nitrite accumulation rate (NAR) was more than 95% after 18 cycles of nitrifying sludge restoration. As a result, HO treatment enabled a nitrifying reactor to recover stable nitritation performance via HO treatment, with the NAR and ammonia removal efficiency (ARE) both exceeding 90%. High-throughput sequencing analysis revealed that HO treatment was successful in restoring nitritation, as the relative abundance of Nitrosomonas in the nitrifying reactor increased from 6.43% to 41.97%, and that of Nitrolancea decreased from 17.34% to 2.37%. Recovering nitritation by HO inhibition is a low operational cost, high efficiency, and non-secondary pollution nitritation performance stabilization method. By leveraging the varying inhibition degrees of HO on AOB and NOB, stable nitrification can be efficiently restored at a low cost and without causing secondary pollution.