EFFECT OF VARIOUS PARAMETERS ON MICROBIAL COMMUNITIES IN MEMBRANE BIOREACTORS TREATING MUNICIPAL WASTEWATER

摘要

Two bench membrane bioreactors (MBRs) were operated at 10-d, 20-d, and 30-d solids retention time (SRT) and no sludge wasting condition treating municipal waste-water and denaturing gradient gel electrophoresis (DGGE) fingerprint analyses were performed to evaluate the effect of SRT, membrane type, presence of anoxic zone, and organic shock loading on microbial communities. Further community analysis was achieved by excising 24 DGGE bands for sequencing and identification. Different SRTs and different membrane modules (flat sheet versus hollow fiber) had minor impacts on mixed liquor (ML) sample microbial communities. However, greater differences in microbial communities were observed between ML and biofilm samples on membranes for all conditions evaluated. Microbial communities in biofilm samples from flat sheet membranes were different than those from hollow fiber membranes. Adding a 7-day organic shock loading to the Enviroquip MBR had little impact on the ML, however the biofilm microbial communities in the shocked unit showed fewer dominant species. Operating the MBRs without an anoxic zone led to an increased number of dominant species, but the dominant species were different in flat sheet and hollow fiber modules. A 16S rRNA clone library was constructed for one sample of mixed liquor (30-d SRT). The phylogenetic distribution found that 62% were from the Proteobacteria class and most of these were Betaproteobacteria (47% of total). A phylogenetic tree analysis of the Betaproteobacteria indicated that 5 species (Ideonella sp., Aquabacerium sp., Dechloromonas sp., Oxalobacterace, and Herbaspirillum sp.) made up 62% of the bacteria in this class.