Evaluating the Impact of Nitrite Concentration on Anaerobic Ammonia Oxidation

The effect of nitrite concentration on anaerobic ammonia oxidation (anammox) was evaluated by short-term batch and long-term fed-batch experiments. The results show that short-term batch tests underestimated the impact of nitrite when present at concentrations that were inhibitory. Despite this, the results from the batch tests also revealed that nitrite inhibition was rapidly reversible. During fed-batch experiments when nitrite concentrations could be sustained for longer periods, inhibition became more pronounced with time for nitrite concentrations higher than 50 mg/L, but did not reflect inhibition for concentrations at 50 mg/L or below. These results show that anammox may be more tolerant to nitrite than previously thought.