Distribution and Activities of Nitrifying and Denitrifying Bacteria in the Lagoon with Intermittent Aeration

Abstract

In the intermittently aerated lagoon, in which high rates of nitrogen removal were observed, counts of nitrifying and denitrifying bacteria were done in every season, with the lagoon water and the mud (settled sludge on the bottom) and nitrifying and denitrifying activities of washed sludge were checked under aerobic or anaerobic conditions. The counts of nitrifying, denitrifying and heterotrophic bacteria were around 2×10³, 1×10⁵ and 2×10⁷ cells/ml, respectively, in water and 8×10³, 2×10⁶ and 7×10⁷ cells/ml, respectively, in mud. Some seasonal change in the population of these bacteria was observed. The nitrifying activity of bacteria in washed sludge suspension with 2mg-N/l of added ammonium was around 1.8mg-N/l•h and the denitrifying activity of bacteria in the same suspension with 2mg-N/l of added nitrate was around 1.4 mg-N/l•h.