Simultaneous nitrification, denitrification, and phosphorus removal from municipal wastewater at low temperature

A lab-scale sequencing batch reactor was employed to study simultaneous nitrification, denitrification, and phosphorus removal (SNDPR) when treating municipal wastewater at 10 °C for 158 days. An anaerobic/aerobic configuration that had previously been effective when treating synthetic wastewater was explored, however, these conditions were relatively ineffective for real municipal wastewater. Incorporation of a post-anoxic phase (i.e., anaerobic/aerobic/anoxic) improved nitrogen and phosphorus removals to 91.1 % and 92.4 %, respectively while achieving a simultaneous nitrification and denitrification efficiency of 28.5 %. Activity tests indicated that 15.8 % and 56.0 % of nitrogen were removed by denitrifying phosphorus accumulating organisms in the aerobic phase and heterotrophs using hydrolyzed carbon in the post-anoxic phase, respectively. 16S rRNA gene analysis and stoichiometric ratios indicated the system was rich in phosphorus accumulating organisms (Dechloromonas and Ca. Accumulibacter). Overall, implementation of the post-anoxic phase eliminated carbon uptake for denitrification in the anaerobic phase and was essential to maintaining SNDPR at low temperatures.