Efficient ammonia-nitrogen removal and recovery from wastewater via the continuous flat-sheet gas-permeable membranes reactor pretreatment

Ammonia‑nitrogen is a crucial component of landfill leachate and a major factor in the eutrophication of aquatic bodies. A novel approach was developed using the continuous flat-sheet gas-permeable membranes (GPMs) reactor pretreatment to efficiently remove and recover ammonia‑nitrogen. The total ammonia‑nitrogen removal efficiency reached 74.2 ± 4.5 % and 66.2 ± 4.9 %, respectively, when simulated nitrogenous wastewater and landfill leachate were treated under the following conditions: influent flow rate 25 L/d, pH 11.0, temperature 25 °C, sulfuric acid absorption concentration 2.5 %, and sulfuric acid absorption flow velocity 70 mL/min. In addition, (NH4)2SO4 (i.e., a crucial ammonia resource) was recovered efficiently, and the flat-sheet GPMs exhibited stable hydrophobic properties. Specifically, the combination of membrane pretreatment and biological treatment reduced the ammonia‑nitrogen concentration from ~230 mg/L (with direct biological treatment only) to ~40 mg/L, with the removal efficiency benefitting from the increase in the chemical oxygen demand/total ammonia nitrogen (COD/TAN) ratio of the leachate after membrane pretreatment. Furthermore, microorganisms that are capable of ammonia‑nitrogen removal (Planktosalinus and Rheinheimera) were selectively enriched. Overall, this study provides a practical method to enhance ammonia‑nitrogen removal and recovery for the treatment of wastewater containing high ammonia‑nitrogen concentrations.