Start-up of partial nitrification by intermittent aeration, pH shocks and sulfide addition in a sequential batch reactor

BACKGROUND: The combination of partial nitrification (PN) and anaerobic ammonium oxidation has been identified as a promising technology for the removal of nitrogenous contaminants from wastewater. The inhibition or wash-out of nitrite-oxidizing bacteria (NOB) while keeping the ammonia oxidizing bacteria (AOB) active is key for PN. Multiple strategies, including intermittent aeration, pH shocks and sulfide addition, were investigated in this study for the start-up of PN and stable suppression of NOB. RESULTS: Intermittent aeration with a dissolved oxygen (DO) level of <5 mg L-1 effectively suppressed NOB activity and resulted in an average nitrite accumulation (NAR) of 93%, implying that the initial DO level during the aeration phase may influence the establishment of successful PN. Likewise, when the reactor was run at a low pH (5), both AOB and NOB activity was reduced. When the pH was raised to neutral pH (7.5), there was an increase in AOB activity with an average NAR of 84%; however, NOB activity remained suppressed. Likewise, when the reactor was fed with sulfide (>= 25 mg L-1) without pH control, the average NAR increased from 63% to 85%. CONCLUSIONS: This study proposes a successful approach to achieving PN by controlling DO level in the aeration phase during intermittent aeration and pH control. The findings also show that the nitrite oxidation process is more sensitive to sulfide than the ammonium oxidation process. As a result, the findings of this study may contribute to a better understanding of establishing PN in a sequential batch system. (c) 2022 Society of Chemical Industry (SCI).

Automated summary

This study investigates various strategies for the start-up of partial nitrification and stable suppression of nitrite-oxidizing bacteria. Controlling the dissolved oxygen level during intermittent aeration and pH plays a crucial role in achieving partial nitrification.