Optimizing ammonia recovery and organic compound removal in high-nitrogen wastewater using anaerobic membrane bioreactor technology: Process efficiency and microbial dynamics

Excess nitrogen in high-strength wastewater represents an environmental burden and an untapped resource for recovery. Conventional nitrogen recovery processes, including ammonia stripping, anammox, and struvite precipitation, require ammonium-rich streams. This study evaluates the potential of an anaerobic membrane bioreactor (AnMBR) as a platform for wastewater treatment, energy recovery, and retention of ammonium (NH 4 ⁺–N) in the permeate. A 340-d trial was conducted with synthetic wastewater across six sequential operating periods with hydraulic retention times (HRTs) of 3–5 d and influent ammonium concentrations of 1170–2800 mg NH 4 ⁺–N L⁻¹. Under the baseline condition (5-d HRT; 1170 mg NH 4 ⁺–N L⁻¹), the reactor achieved 98% COD removal, 90% ammonium retention, and methane production of 0.28 L CH 4 g COD⁻¹ d⁻¹. At a 3-d HRT or at higher influent ammonium concentrations, process stability declined, with lower COD removal and ammonium retention accompanied by volatile fatty acid accumulation. Descriptive microbial profiles showed enrichment of stress-tolerant taxa and a shift from acetoclastic to hydrogenotrophic methanogenesis. The principal contribution is therefore the long-term operational evidence that an AnMBR can produce an ammonium-rich, solids-free permeate that may serve as a feed for downstream nitrogen-recovery processes, while defining the operational conditions associated with stable performance.