Shortcut nitrification-denitrification and biological phosphorus removal in acetate- and ethanol-fed moving bed biofilm reactors under microaerobic/aerobic conditions

This study investigated the feasibility of coupling simultaneous partial nitrification and denitrification (SPND) to biological phosphorus removal in continuous-flow intermittently-aerated moving bed biofilm reactors (MBBRs) fed with different carbon sources, i.e. ethanol and acetate. Bacterial cultivation at pH 8.2 (±0.2), 26-28 °C and SRT of 4 day and microaerobic/aerobic MBBR operation allowed to achieve average dissolved organic carbon (DOC), total inorganic nitrogen (TIN) and P-PO43- removal efficiencies (REs) of 100%, 81-88% and 83-86% at HRT of 1 day, dissolved oxygen (DO) range of 0.2-3 mg L-1 and feed C/N and C/P ratios of 3.6 and 11, respectively. Acetate supplementation favored a diversified microbial community, while overgrowth of heterotrophs was observed when increasing feed C/N ratio in ethanol-fed MBBR. Illumina sequencing displayed the presence of putative phosphorus accumulating organisms (PAOs) such as Hydrogenophaga and Pseudomonas in MBBR biofilm and suspended biomass, whereas no typical NOB was identified during the study