Novel strategy for rapid start-up and stable operation of anammox: Negative pressure coupled with the direct-current electric field

An application challenge of anaerobic ammonia oxidation (anammox) is the slow proliferation rate of anaerobic ammonium oxidation bacteria (AnAOB). This study adopted negative pressure coupled with the direct-current electric field (NP-DCEF) to evaluate system nitrogen removal performance. Results showed that the total nitrogen removal rate (TNRR) of the NP-DCEF system was stable at 88.6% after seven days. Compared with that of the ordinary operating system (45.4%), the relative abundance of Candidatus-kuenenia considerably increased from 51.9% to 57.6%. Under transient and long-term influent fluctuation, the NP-DCEF system showed high nitrogen removal performance. The specific activity of AnAOB (SAA) reached 11.0 mg N∙g Vss^-1 h^-1 under load fluctuation, and it was 8.7 mg N∙g Vss^-1 h^-1 under ordinary operational conditions. In addition, the specific activities of hydrazine dehydrogenase (HDH) and hydrazine synthetase (HZS) reached 32.66 and 92.95 U∙L^-1, which are considerably higher than those under the ordinary operating conditions (18.41 and 63.20 U∙L^-1). These results indicated that the novel operation strategy has specific feasibility and potential for the start-up and long-term operation of anammox.