Effect of temperature and dissolved oxygen on biological nitrification at high ammonia concentrations.

Effect of temperature and dissolved oxygen concentration on nitrification rate were investigated with enrichment cultures of nitrifying bacteria. Values of specific nitrite oxidation rate in the absence of ammonia were 2.9-12 times higher than maximum specific ammonia oxidation rates at the same temperatures. The presence of high ammonia levels reversed this relationship, causing maximum specific nitrite oxidation rates to fall to 19 to 45% as high as maximum specific ammonia oxidation rates. This result suggests that nitrification at high ammonia levels will invariably result in nitrite accumulation. The KO2 for nitrite oxidation in the presence of high ammonia levels was higher than the KO2 for ammonia oxidation when temperature exceeded 18°C, whereas the opposite was true at lower temperatures. These results indicate that low oxygen tensions will exacerbate nitrite accumulation when water temperature is high.