Microbial population analysis of nutrient removal-related organisms in membrane bioreactors

Abstract

Membrane bioreactors (MBR) are an important and increasingly implemented wastewater treatment technology, which are operated at low food to microorganism ratios (F/M) and retain slow-growing organisms. Enhanced biological phosphorus removal (EBPR)-related organisms grow slower than ordinary heterotrophs, but have never been studied in detail in MBRs. This study presents a comprehensive analysis of the microorganisms involved in EBPR in pilot-and full-scale MBRs, using fluorescence in situ hybridization (FISH), as well as an overall assessment of other relevant microbial groups. The results showed that polyphosphate accumulating organisms (PAOs) were present at similar levels in all studied MBRs (10%±6%), even those without a defined anaerobic zone. Glycogen accumulating organisms were also detected, although rarely. The FISH results correlated well with the observed P removal performance of each plant. The results from this study suggest that a defined anaerobic zone is not necessarily required for putative PAO growth in MBRs, since polyphosphate storage may provide a selective advantage in fulfilling cell maintenance requirements in substrate-limited conditions (low F/M).

Preparation and characterization of antifouling graphene oxide/polyethersulfone ultrafiltration membrane: Application in MBR for dairy wastewater treatment

“…Conventionally, systems that are projected to remove phosphorus should have aerobic and anaerobic reactors in series in order to the selection and growth of phosphate accumulating microorganisms (PAOs) [53]. However, MBRs present a potentially suitable environment for PAOs proliferation because the high biomass concentrations in MBRs might lead to microzone of anoxic or anaerobic within the sludge flocs [54]. In the case of conventional biological treatment systems, partial removal of phosphorus occurs through its assimilation by the biomass for cellular synthesis [4,39].…”

Characterization of Microbial Community in Membrane Bioreactors Treating Domestic Wastewater

“…Few studies have characterized the bacterial community structures in full-scale MBRs treating domestic wastewater (Wan et al, 2011;Yu et al, 2011;Silva et al, 2012), but several studies have conducted experiments with lab-scale or pilot-scale MBRs (Miura et al, 2007;Molina-Muñoz et al, 2009). Wan et al (2011) reported that the microbial community in an MBR is constantly distinct from that in a parallel-running conventional activated sludge process and that novel 16S rRNA gene sequences were detected frequently in clone libraries from the MBR.…”

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes

“…Azoarcus, Thauera and Paracoccus, for example, are commonly detected in aerobic PHA producing mixed microbial cultures [48]. In the same way, PAOs and GAOs have been previously observed in plants not designed for EBPR [49], suggesting that it is possible that PAO and GAO metabolism is flexible and they could survive aerobically.Three of the microbial groups studied, i.e. denitrifying bacteria, SRB and methanogenic archaea, were detected in both processes (Figure 1).…”