Partial nitrification via nitrite at ordinary and low temperatures in an SBR treating domestic wastewater

Through real-time aeration duration control, partial nitrification was carried out in a lab-scale SBR at normal temperatures and maintained for a long time even at low temperatures. The specific ammonia oxidation rate would be reduced with decrease of the temperature. The average specific ammonia oxidation rate at 27°C was 1.68 times of that at 13°C. The temperature coefficient of ammonia oxidation reaction in the reactor was ascertained 1.501 according to the Arrhenius expression. When nitrite accumulation ratio was steadily kept over 90%, fluorescence in situ hybridization (FISH) was used to detect the sludge population structure, which showed the proportion of the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was 8%~9% and lower than 0.5%, respectively. The real-time control strategy had a positive effect on the enrichment of AOB and the limitation or wash-out of NOB. An advisable start up strategy to operate a partial nitrification system at low temperatures could have two steps, obtaining firstly the selective enrichment of AOB as well as the washout of NOB by real-time aeration duration control under ordinary temperatures, and then making the biomass slowly adapt to low temperatures