Abstract
Microorganisms associated with the foam and their status before and after foaming in a submerged membrane bioreactor situated in Japan, are described. The microorganisms associated with membrane bioreactors have not yet been fully explored, as this is a relatively recent technology. An important finding was that one of the most discussed filaments Microthrix parvicella, the occurrence of which has rarely been reported in Japan, dominated in the foam of this bioreactor. Various types of filaments were identified in the foam based on morphology and available specifies-specific oligonucleotide probes but they were mainly Nocardia spp., Microthrix parvicella, Nostocoida limicola, type 1851, type 0041, type 1701, type 0675, type 021n, type 0914 etc. Also Microthrix pervicella, species from Mycolata groups and total eubacteria in the before and after foaming-samples were quantified using the oligonucleotide probes MPA 223, MYB and EUB, respectively. The ratio of MPA to EUB (approx. 22%) in the foam was found to be much higher than the ratio of MYB to EUB (approx. 6%). The investigation suggested that Microthrix parvicella was mainly responsible for the onset of foaming in this plant. This study provides information about the occurrence, composition and ratio of foaming filaments that might occur in a membrane bioreactor (MBR) along with the most important and discussed filament Microthrix parvicella.
