Combining simultaneous nitrification-endogenous denitrification and phosphorus removal with post-denitrification for low carbon/nitrogen wastewater treatment.

Due to the limited nutrient removal from low carbon/nitrogen (⩽4) wastewater, a process combined simultaneous nitrification-endogenous denitrification and phosphorus removal (SNDPR) with post-denitrification (PD) in a SBR was proposed for deep-level nutrient removal without external carbon addition. SNDPR driven by PAOs and GAOs reduced PO4(3-)-P (98.3%) and partial TN (59.0%) at low DO conditions (0.5±0.1mg/L), and post-dentrification achieved further NOX(-) (produced by SNDPR) removal (24.0%) anoxically by utilizing the residual intracellular polymers in GAOs. Combined control of anaerobic/aerobic/anoxic durations and low DO inhibition to aerobic GAOs and NOB conducted partial nitrification-endogenous denitrification (PNED) (66%), which saved 44.3% intracellular polymers to further reduce 64% TN in effluent. After 115-day operation, the average effluent PO4(3-)-P and TN concentrations were 0.4 and 3.9mg/L, respectively, with 92.1% of TN removal. Highly enriched PAOs (36%±2%), GAOs (22%±2%) and AOB (15%±3%) over NOB (3%±1%) facilitated P uptake, PNED and post-denitrification in the SNDPR-PD system.