Membrane Biofilm Development for Improved Domestic Wastewater Treatment at Low Temperatures using Anaerobic Membrane Bioreactor

Membrane biofilm development was evaluated to improve treatment of domestic wastewater in low-temperature anaerobic membrane bioreactor (AnMBR). Three levels of membrane fouling were compared based on transmembrane pressure (TMP) in a bench-scale system with replicate membrane housings, separate permeate collection, and independent biogas sparging control. Permeate chemical oxygen demand (COD) was reduced by over 50 mg/L under high fouling conditions. However, permeate dissolved methane concentration was 2-3 times the predicted concentration by Henry’s Law at saturation. Increasing biogas sparging to restore fouled membranes to neutral TMP did not negatively impact biofilm treatment performance. This suggests that the biologically active biofilm was tightly adhered to the membrane surface and could remain active without an appreciable impact on TMP. In the absence of high TMP, dissolved methane oversaturation persisted implying that methanogenesis in the biofilm was the primary driving force in methane oversaturation, not high TMP. RNA-based 16S rRNA sequencing, reverse transcription quantitative PCR (RT-qPCR) targeting the methyl coenzyme-M-reductase (mcrA) gene, and performance observations indicated that the biofilm was comprised of a specialized microbial community enriched in highly active methanogens and syntrophic bacteria. The results describe a potentially attractive strategy to reduce effluent COD of low-temperature AnMBR by supporting syntrophy and methanogenesis in the membrane biofilm.