Nitrification–denitrification via nitrite in SBR using real-time control strategy when treating domestic wastewater

Abstract

A lab-scale sequencing batch reactor (SBR) was employed to treat low C/N ratio municipal wastewater to investigate the stability of nitrification–denitrification via nitrite using a real-time control strategy to switch aeration on and off. Three parameters, pH, DO and ORP, were selected as control parameters in the SBR reactor operation. Nitrite accumulation was observed under real-time control conditions (NO 2 −-N/NO x −-N > 0.8), implying that nitrification–denitrification mainly via nitrite was achieved by the process control strategy applied. The nitrite concentration in the SBR decreased sharply when the SBR system was operated using a fixed time aeration control strategy for 7 days. Ammonia nitrogen concentration (NH 4 +-N) and temperature also affect nitrite accumulation. Ammonia shock loads limited nitrification due to alkalinity limitations, but the system recovered quickly from short-time high ammonia shock loads when the real-time control strategy was applied. Temperature was observed to affect nitrite accumulation rate when the real-time control strategy was used in the SBR reactor, with higher nitrite accumulation at 28 ± 0.5 °C (NO 2 −-N/NO x −-N = 0.84), compared to the accumulation at the ambient average temperature of 20 °C (NO 2 −-N/NO x −-N > 0.61).