The effects of low oxidation-reduction potential on the performance of full-scale hybrid membrane-aerated biofilm reactors

• Full-scale hybrid MABRs fed with anaerobic sludge were monitored for three years. Nitrification performance was lowest at the ORP. Nitrifying organisms’ abundance significantly higher highest High of Fe and S compounds in MABR biofilm under Membrane-Aerated Biofilm Reactors (MABRs) are becoming a popular process intensification alternative within wastewater treatment plants (WWTP). Indeed, nitrogen removal capacity aerobic/anoxic/anaerobic reactors can be substantially enhanced reduced energy consumption footprint requirements. However, little is known about how oxidation-reduction potential (ORP) may impact their overall performance. This study aims to report some these effects by showing results almost years monitoring two (R1, R2) adjacent an existing Biodenipho™ facility. In Period 1 (P1), R1 R2 mixed liquor from selector biological phosphorus zone. 2 (P2), external aeration introduced increase ORP values R2), membranes replaced (R1) or cleaned (R2). Results show nitrification rates: 0.27 0.33 g N m -2 d -1 R1/R2 during P1 1.0 0.80 P2. 16s rRNA amplicon sequencing analysis revealed that relative nitrifying organisms increased 0.2 6.7% 0.8 5.3% P2 (in detriment microbes fermenting capabilities). Energy dispersive X-ray spectroscopy confirmed presence coating substances which could pyrite its precursors like mackinawite. Overall, it hypothesized low conditions (P1) had detrimental effect on performance, as promoted reduction different iron sulfur compounds, turn a) precipitate FeS increasing mass transfer limitations competing biomass space; b) re-oxidize internal oxygen demand; c) inhibit nitrifiers growth.