Analyses of bioflocculation and bacterial communities in sequencing batch reactors

Laboratory experiments were carried out to investigate effects of the sludge retention time (SRT) feeding and organic loading on bioflocculation and bacterial community of activated sludge. Batch scale conventional activated sludge reactors and sequencing batch reactors (SBR) fed on a synthetic wastewater contained different carbon source were operated at an SRT of 5, 10, and 20 days after changing running parameters, that is, the SRT from 5 to 10 days, and feeding from acetate to glucose, and three-time shock loading, the extracellular polymeric substances (EPS), sludge volume index (SVI), and effluent suspended solid (ESS) as well as the bacterial community characterized with denaturing gradient gel electrophoresis (DGGE) were studied. The results showed that longer SRT benefited the settling ability of activated sludge with little change of bacterial community, while alternate substrates and higher organic loading led to higher SVI and deteriorating ESS, which may be caused by shifting of microorganism community.