Nitrogen Removal from Real Sewage Pretreated with Anaerobic Membrane Bioreactors Using One-Stage Partial Nitritation-Anammox Process with Hydroxyapatite Crystallization and Partial Nitritation-Anammox Granule

To apply the one-stage partial nitritation-anammox (PNA) process to municipal mainstream wastewater, an experiment on continuous nitrogen removal using hydroxyapatite crystallization and partial nitritation-anammox (HAP-PNA) granule was conducted at 25 °C using real sewage pretreated with anaerobic membrane bioreactors (AnMBR). In the sewage adaptation period, the ammonium concentration of the sewage was firstly adjusted to 150 mg-N L and then gradually decreased to 100 and then to 50 mg-N L. Finally, the real sewage treatment with the ammonium concentration of 33 mg-N L for long-term operation at HRT of 2 h. Results of the continuous feeding tests for the real sewage treatment, showed that a nitrogen removal efficiency of 87% was obtained at HRT of 2 h, and the rates of ammonium oxidation and nitrogen removal by anammox bacteria were 0.20 and 0.34 kg-N (m d), respectively. From the results of microbial analysis, the top two dominant species were the anammox bacteria and AOB, with relative abundances of 30.2% (Candidatus Kuenenia stuttgartiensis) and 13.6% (Nitrosomonas sp.), respectively. Therefore, it was shown that AOB and anammox bacteria involved in the PNA process could be maintained during the real sewage treatment. This is the first demonstration of the successful operation and stable high performance of the PNA process with HAP-PNA granule for treating mainstream sewage.