Mainstream deammonification at ambient temperature treating real sewage by a plug-flow fixed-bed reactor based on...

A plug-flow fixed-bed reactor (PFBR) with zeolite/tourmaline-modified polyurethane (ZTP) carriers (PFBR_ZTP) was constructed to realize mainstream deammonification for real domestic sewage treatment. The PFBR_ZTP and PFBR were operated for 111 days treating aerobically pretreated sewage in parallel. A higher nitrogen removal rate of 0.12 kg N·(m³·d)^-1 was achieved in PFBR_ZTP despite lowering the temperature (16.8-19.7 °C) and fluctuating water quality. Meanwhile, it was indicated that anaerobic ammonium oxidation dominated (64.0 ± 13.2%) in PFBR_ZTP, by nitrogen removal pathway analysis and high anaerobic ammonium-oxidizing bacteria (AnAOB) activity (2.89 mg N·(g VSS·h)^-1). And, the lower protein/polysaccharides (PS) ratio further indicated a better biofilm structure in PFBR_ZTP owing to a higher abundance of microorganisms relevant to PS and cryoprotective EPS secretion. Furthermore, partial denitrification was an important nitrite supply process in PFBR_ZTP based on low AOB activity/AnAOB activity ratio, higher Thauera abundance and a remarkably positive correlation between Thauera abundance and AnAOB activity.