Impact of operational parameters on bacterial community in a full-scale municipal wastewater treatment plant

A bacterial community in activated sludge from a full-scale municipal wastewater treatment plant was monitored throughout the year with the use of FISH, RISA and DGGE techniques. In the investigated range of temperatures (11.9-21.6 degrees C), a rise in temperature resulted in a lower total bacteria richness, while organic load rate changes from 0.09 to 0.21 g COD x g TSS(-1) x d(-1) were positively correlated with the number of bands in RISA patterns. The most diverse pattern (29 different bands) was characteristic for the activated sludge sample collected at the end of January at wastewater temperature of 11.9 degrees C. The ammonia-oxidising bacteria community did not change during the study, and comprised of 4 different bacterial populations with one dominant species closely related to Nitrosospira sp. REGAU (GenBank accession number AY635572.1). The percentage of ammonia-oxidising bacteria in the activated sludge varied from 6.2 to 19.5% and depended on temperature (R = 0.61, p = 0:02) and organic load rate (R = -0.55, p = 0.04).