High-performance system for partial nitritation of reject water resistant to temperature fluctuation

A sequencing batch reactor (SBR) applying partial nitritation for reject water treatment was operated for 330 days at a laboratory scale. The system was repeatedly exposed to sudden temperature drops from 24 to 17 °C. The nitrogen loading rate (NLR) was increased incrementally from 0.4 to 1.5 kg/(m3 day) with the aim to evaluate temperature stability of the process at different NLR value. Total nitrite nitrogen (TNIIIN) represented 94–99% of oxidised nitrogen in the effluent throughout the entire operation of the reactor. It was found that the pH profile during the SBR cycle, nitrogen removal efficiency and concentration of N-species in the effluent did not show significant changes following temperature decreases occurring within the entire applied range of the NLR. Simultaneously, the nitrogen removal rate increased proportionally with the NLR where the nitrogen oxidation efficiency reached 48–58% regardless of actual temperature and NLR. These observations clearly demonstrate the temperature stability of applied partial nitritation system during the tested temperature fluctuations.