Energy-positive food wastewater treatment using an anaerobic membrane bioreactor (AnMBR)

An immersed-membrane anaerobic membrane bioreactor (AnMBR) achieved 88-95% of COD removal for meat-processing wastewater at organic loading rate (OLR) of 0.4-3.2 kgCOD m−3 d−1. Membrane flux was stable for low OLR (0.4 and 1.3 kgCOD m−3 d−1), but irrecoverable fouling occurred at high OLR of 3.2 kgCOD m−3 d−1. Methane gas yield of 0.13-0.18 LCH4 g−1CODremoved was obtained, which accounted for 33-38% of input COD, the most significant electron sink. Dissolved methane was only 3.4-11% of input COD and consistently over-saturated at all OLR conditions. The least accumulation of dissolved methane (25 mg L−1 and saturation index 1.3) was found for the highest OLR of 3.2 kgCOD m−3 d−1 where biogas production rate was the highest. Energy balances showed that AnMBR produced net energy benefit of 0.16-1.82 kWh m−3, indicating the possibility of energy-positive food wastewater treatment using AnMBRs.