Advanced Polishing of Municipal Anaerobic Treatment Effluent for Water Reuse and Nitrogen Recovery Using UF–RO–Membrane Contactor Integration

Anaerobic biological process, such as Upflow Anaerobic Sludge Blanket (UASB) reactors, efficiently remove solids and organic matter from municipal wastewater but typically show limited ammonia removal, which can contribute to eutrophication. Guided by circular economy principles, this study evaluates an integrated ultrafiltration - reverse osmosis - membrane contactor (UF-RO-MC) train to polish municipal UASB effluent for non-potable reuse and concentrate and recover nitrogen as an ammonium sulfate product. UF provided stable turbidity control and improved feed-water quality for RO. RO produced a higher quality permeate (COD < 10 mg/L, PO4: <1 mgL; and N-NH 3 : 1.9 mg/L) and concentrated dissolved constituents, including ammonia, enabling downstream recovery. Fouling assessments indicated predominantly reversible fouling in UF and a higher irreversible fraction in RO, mostly associated with soluble organic matter and refractory fractions as seen by excitation-emission matrices. In the membrane contactor, ammonia removal and recovery increased with pH and temperature. The most cost-effective operating point was achieved at ambient temperature (25 °C) with pH adjustment to 10, reaching ~90% recovery from RO concentrate, equivalent to 0.13 kg NH3 recovered per m³. A screening-level scale-up to a full-scale WWTP scenario suggests that combined reuse-water production and nitrogen recovery can provide an attractive resource-recovery pathway. • UF-RO permeate is suitable for non-potable reuse (low turbidity, salinity and SAR). • RO concentrated ammonia (2.2×) for recovery. • EEM tracked OM behavior across UF and RO and supported process interpretation. • Fouling shifted from mainly reversible in UF to more irreversible in RO • Membrane contactor achieved ~90% recovery at 25 °C and pH 10 with favorable costs.