Nitrogen removal via nitrite in domestic wastewater treatment using combined salt inhibition and on-line process control

Nitrogen removal through the nitrite pathway has been successfully achieved using on-line aeration length control. However, it takes a long time period to get steady performance when using on-line control as the sole strategy. On the other hand, salt inhibition has also been used to achieve the nitrite pathway, with potentially adverse effects on the overall microbial community at high salt concentrations. The objective of this study is to develop a control strategy based on the combination of low salt inhibition levels and on-line control to accelerate the achievement of nitrite pathway in a sequencing batch reactor (SBR) treating domestic wastewater. Salt concentrations and on-line control parameters were chosen in batch tests. The recovery of the nitrite-oxidizing bacteria (NOB) activity was examined after stopping on-line control and salt dosing. The findings clearly show that combining salt inhibition at low salinity (5 g/L) with on-line pH control is an efficient strategy to achieve nitrogen removal via nitrite quickly and steadily.