Analysis of filamentous bacteria from a foaming and bulking activated-sludge plant in north China

For full understanding of the microbial community in the aeration tank of WWTPs (wastewater treatment plants), one of the feasible and effective ways is to investigate the massive genetic information contained in the activated sludge. In this study, 3 different sludge samples were collected, which were the pre-foaming and pre-bulking sludge (PFBS), the foaming and bulking sludge (FBS) and the normal sludge (NS), respectively. 454 high-throughput pyrosequencing was applied to analyze bacterial 16S rRNA genes. In total, 19521, 101772 and 35172 effective sequence reads were obtained for these 3 samples. The taxonomic complexities were compared at phylum and genus levels. The results showed that the dominant filamentous bacteria belonged to the phylum Actinobacteria in the foaming and bulking sample was the genera Candidatus ‘Microthrix parvicella’. Genera Tetrasphaera belonged to the phylum Actinobacteia and Trichococcus belonged to the phylum Firmicutes were also very important in sludge foaming and bulking phenomenon. Real-time PCR assays of the 18 samples demonstrated that above 3.86% Candidatus ‘Microthrix parvicella’ in activated sludge could cause foaming and bulking problems. These data illustrate that Candidatus ‘Microthrix parvicella’ are a group of filamentous microorganisms influencing the sludge foaming and bulking occurrence in this sludge wastewater treatment plant.