Studies on the high rate removal of nitrogen in a lagoon with intermittent aeration. IV. Distribution and activities of nitrifying and denitrifying bacteria in the lagoon with intermittent aeration.

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.