Gel-immobilized partial nitritation/anammox achieves reliable nitrogen removal at different concentrations of nitrogen and reactivation processes

A two-stage partial nitritation/anammox process based on microbial encapsulation (PN/A-E) was established. The nitrogen removal characteristics of PN/A-E under high and low ammonia nitrogen and after reactivation following a long-term shutdown were comprehensively investigated and compared with anammox granular sludge (AnGS). The stable PN process did not depend on high ammonia nitrogen, and the nitrite accumulation rate reached 95.2 +/- 0.7 %. The overall nitrogen removal rate of encapsulated anammox bacteria was twice that of the AnGS, and it was more tolerant to external interference. Moreover, PN/A-E showed good reactivation performance, and the total nitrogen in the effluent was 10.0 +/- 1.4 mg center dot L-1 when the final hydraulic retention time was 2.18 h. The immobilized fillers support an increase in ammonia-oxidizing bacteria under restricted conditions and were more conducive to the dominance of functional bacteria and the stability of microbial community under low ammonia nitrogen. This study provides a positive method to achieve a reliable PN/A.

Automated summary

A two-stage partial nitritation/anammox process based on microbial encapsulation (PN/A-E) was established and thoroughly studied. The nitrogen removal efficiency of PN/A-E was compared to anammox granular sludge (AnGS) under high and low ammonia nitrogen conditions, as well as after reactivation from a long-term shutdown. The results showed that PN/A-E had a stable performance even under high ammonia nitrogen, and the nitrite accumulation rate reached 95.2 +/- 0.7%. The total nitrogen removal rate of encapsulated anammox bacteria was twice that of AnGS, and it exhibited better resilience to external interference. PN/A-E also demonstrated good reactivation performance with a final effluent total nitrogen of 10.0 +/- 1.4 mg·L-1 at a hydraulic retention time of 2.18 h. The immobilized fillers facilitated the growth of ammonia-oxidizing bacteria under restricted conditions and promoted the dominance of functional bacteria and stability of microbial community under low ammonia nitrogen. This study provides a positive method for achieving reliable PN/A process.