Using Partial Nitrification and Anammox To Remove Nitrogen from Low-Strength Wastewater by Co-immobilizing Biofilm inside a Moving Bed Bioreactor

Abstract

The stable operation of partial nitrification and anammox (PNA) process is a challenge in nitrogen removal from extremely low-strength ammonia wastewater like sewage mainstream. A moving bed reactor with functional carriers (30% filling rate) was developed to treat a synthetic influent with 50 mg/L ammonia. The long-term operation results showed nitrogen removal efficiencies of 71.7 ± 9.1% have been stably obtained under a relatively short hydraulic retention time of 2 h. Microbial analysis revealed anammox bacteria and ammonium oxidizing bacteria (AOB) with 29.7% and 6.32% abundance were the two most dominant bacteria in the reactor. Carriers largely retained slow-growing anammox bacteria in their hollow space and established a sandwich-like biofilm structure of co-immobilization of anammox bacteria and AOB. The anammox activity was much higher in carrier biofilms than in suspended flocs, while, for the AOB activity, the situation was reversed. Correspondingly, a fluorescent in situ hybridization analysi...