Characterization of the bacterial community involved in the bioflocculation process of wastewater organic matter in high-loaded MBRs

Abstract

High-loaded membrane bioreactors (HL-MBRs), i.e., bioreactors equipped with a membrane for biomass retention and operated at extremely short sludge and hydraulic retention times, can concentrate sewage organic matter to facilitate subsequent energy and chemical recovery from these organics. Bioflocculation, accomplished by microorganisms that produce extracellular polymers, is a very important mechanism in these reactors. Bacterial diversity of the sludge and supernatant fraction of HL-MBRs operated at very short sludge retention times (0.125, 0.5, and 1 day) were determined using a PCR-denaturing gradient gel electrophoresis (DGGE) and clone library approach and compared to the diversity in sewage. Already at a sludge retention time (SRT) of 0.125 day, a distinct bacterial community developed compared to the community in sewage. Bioflocculation, however, was low and the majority of the bacteria, especially Arcobacter, were present in the supernatant fraction. Upon increasing SRT from 0.125 to 1 day, a much stronger bioflocculation was accompanied by an increased abundance of Bacteroidetes in the (solid) sludge fraction: 27.5 % at an SRT of 0.5 day and 46.4 % at an SRT of 1 day. Furthermore, cluster analysis of DGGE profiles revealed that the bacterial community structure in the sludge was different from that in the supernatant. To localize specific bacterial classes in the sludge flocs, fluorescence in situ hybridization (FISH) was carried out with three different bacterial probes. This showed that Betaproteobacteria formed clusters in the sludge flocs whereas Alphaproteobacteria and Gammaproteobacteria were mainly present as single cells.

Rheology and Microbiology of Sludge from a Thermophilic Aerobic Membrane Reactor

“…Almost all the biological processes have been explored in terms of biomass composition (bacteria, protozoa, metazoan, and fungi) and activity: conventional activated sludge, attached biomass, membrane reactors, and treating either municipal [27][28][29][30][31][32][33][34] or industrial wastewater [35][36][37][38][39]. Likewise, identification and quantification of microorganisms operating under different conditions (aerobic, anoxic, and anaerobic) have been reported [25,[40][41][42][43][44][45][46].…”

“…Scientific literature reports hundreds of applications of conventional and innovative biological tools, as well as examples of investigations based on ecological criteria [9,[20][21][22][23][24][25][26][27]. Almost all the biological processes have been explored in terms of biomass composition (bacteria, protozoa, metazoan, and fungi) and activity: conventional activated sludge, attached biomass, membrane reactors, and treating either municipal [27][28][29][30][31][32][33][34] or industrial wastewater [35][36][37][38][39].…”

Colonization kinetics and implantation follow-up of the sewage microbiome in an urban wastewater treatment plant

“…Among the Chitinophagales, Ferruginibacter is among the top 10 bacterial predominant OTUs; represents 1.5% of the total reads within the third period of colonization of the SM_WWTP. Previous studies reported that Ferruginibacter are highly enriched in sludge and potentially associated with www.nature.com/scientificreports/ bio-flocculation and biofilms 53,54 consistently supporting their suggested role in floc formation. In a recent report, Saunders et al, analyzed the microbial communities in 13 Danish wastewater treatment plants in consecutive years and a single plant periodically over 6 years, using Illumina sequencing of 16S ribosomal RNA amplicons of the V4 region 4 .…”

Investigating the performance and mechanism of nitrogen gas fixation and conversion to ammonia based on biocathode bioelectrochemistry system

“…Consequently, the experiments of varying applied voltage demonstrated that large current was favorable for electron transfer for efficient NH 4 + production. However, studies have shown that different microorganisms have different tolerances to voltages, and high applied voltages make microorganisms more sensitive and inhibit growth, eventually becoming inactive 37 . Meanwhile, in order to avoid over‐occurrence of water splitting side‐reaction, the maximum voltage applied was only 1.5 V.…”

“…However, studies have shown that different microorganisms have different tolerances to voltages, and high applied voltages make microorganisms more sensitive and inhibit growth, eventually becoming inactive. 37 Meanwhile, in order to avoid overoccurrence of water splitting side-reaction, the maximum voltage applied was only 1.5 V.…”