Population dynamics in a sequencing batch reactor fed with glucose and operated for enhanced biological phosphorus removal.

The study investigated the effect of glucose feeding as the sole carbon source on population dynamics in a sequencing batch reactor (SBR) operated for enhanced biological phosphorus removal (EBPR). The lab-scale SBR operation was started with a biomass taken from a WWTP plant performing EBPR and continued around two months. It exhibited a sequence of periods with different performance and biomass characteristics. The first period indicated predominant EBPR activity, involving phosphorus release in the anaerobic phase with PHA production as expected. Lactate generated from glucose fermentation was presumably converted to PHA by PAOs as an essential part of the EBPR activity. In the second period a major shift occurred in the population dynamics favoring the preferential growth and the predominance of GAOs which have the advantage of utilizing glucose directly and eventually the EBPR activity was deteriorated. The significant feature of the third period was the proliferation of filamentous microorganisms.

Production of polyhydroxyalkanoates (PHA) by activated sludge treating municipal wastewater: effect of pH, sludge retention time (SRT), and acetate concentration in influent.

In this paper, the production of biodegradable plastics polyhydroxyalkanoates (PHA) by activated sludge treating municipal wastewater was investigated. The effect of three operational factors, i.e. the acetate concentration in influent, pH, and sludge retention time (SRT) were studied. Sludge acclimatized with municipal wastewater supplemented with acetate could accumulate PHA up to 30% of sludge dry weight, while sludge acclimatized with only municipal wastewater achieved 20% of sludge dry weight. It was found that activated sludge with an SRT of 3 days possessed better PHA production capability than sludge with an SRT of 10 days. Sludge acclimatized under pH 7 and 8 conditions in sequencing batch reactors (SBRs) exhibited similar PHA production capability. However, in PHA production batch experiments, pH value influenced significantly the PHA accumulation behavior of activated sludge. When pH of batch experiments was controlled at 6 or 7, a very low PHA production was observed. The production of PHA was stimulated when pH was kept at 8 or 9.