Mainstream partial denitrification-anammox (PD/A) for municipal sewage treatment from moderate to low temperature: Reactor performance and bacterial structure

Anammox is sensitive to temperature, which can limit its practical application in wastewater treatment. In this study, a step-feed anoxic-oxic (A/O) process coupled with PD/A was operated steadily from 26.8 °C to 13.1 °C for wastewater treatment for 200 days. The effluent total inorganic nitrogen (TIN) and phosphorus concentrations were 10.2 mg/L and 0.29 mg/L at C/N ratio of 4.6 and 15.0 °C even with increasing nitrogen loading rate (NLR). The anammox activity was 5.60 mg NH4+-N/gMLSS/d even at 14 °C, moreover, anammox abundance on the biocarriers increased with decreasing temperature. It was observed that the effect of partial denitrification (PD) was enhanced under low temperature, thus the contribution of anammox for nitrogen removal was improved. The pathway of anammox for nitrogen removal accounted for 48% and the effect of effluent did not deteriorate under low temperature. This study states that PD/A has advantages under low temperature operation, which is suitable for treatment of wastewater with low C/N ratio.