Performance analysis and optimization of ammonium removal in a new biological folded non-aerated filter reactor.

A new type of biological folded non-aerated filter (BFNAF) was found to be superior and feasible for the treatment of NH4+-N wastewater. It was constructed with the folded structure suitable for the nylon biomass carrier. The advantages of the BFNAF included low energy consumption, long reaction path, large biofilm surface area and non-clogging compared to the traditional biological aerated filter. In this study, the effects of hydraulic retention time (HRT), and the influent NH4+-N concentration on the performance of BFNAF were investigated and optimized by the response surface methodology. Under the optimal operating condition (HRT, 10 h; NH4+-N concentration, 52 mg/L), the removal efficiency and removal rate were 94.62 ± 0.63% and 0.106 kg-NH4+ m-3 day-1, respectively. The results showed that the BFNAF reactor could remove NH4+-N from wastewater and realized the nitrification process effectively under natural ventilation conditions.