Occurrence and activity of sulphate reducing bacteria in aerobic activated sludge systems

In the sewage or wastewater treatment plant, biological sulphate reduction can occur spontaneously or be applied beneficially for its treatment. The results of this study can be applied to control SRB in the sewage and WWTP. Therefore, population diversity analyses of SRB for nine activated sludge wastewater treatment plants (WWTP) in the Netherlands and the effect of long-term (months) oxygen exposures on the SRB activity were carried out. T-RFLP and clone sequencing analyses of winter and summer samples revealed that (1) all WWTP have a similar SRB population, (2) there is no seasonal impact (10–20 °C) on the SRB population present in the WWTP and (3) Desulfobacter postgatei, Desulfovibrio desulfuricans and Desulfovibrio intestinalis were the most common and dominant SRB species observed in these samples, and origin from the sewage. Short term activity tests demonstrated that SRB were not active in the aerobic WWTP, but while flushed with N₂-gas SRB became slightly active after 3 h. In a laboratory reactor at a dissolved oxygen concentration of <2 %, sulphate reduction occurred and 89 % COD removal was achieved. SRB grew in granules, in order to protect themselves for oxygen exposures. SRB are naturally present in aerobic WWTP, which is due to the formation of granules.