Impact of sludge retention time on the fine composition of the microbial community and extracellular polymeric substances in a membrane bioreactor.
Membrane bioreactors (MBRs) are an advanced technology for wastewater treatment whose wide application has been hindered by rapid fouling of the membranes. MBRs can be operated with long sludge retention time (SRT), a crucial parameter impacting microbial selection in the reactor. This also affects filtration performance, since a major fouling agent are the extracellular polymeric substances (EPS). In this study, the impact of the SRT on the ecophysiology of the MBRs and, consequently, on membrane fouling was evaluated. A MBR was operated under a SRT of 60 days followed by a SRT of 20 days. A comprehensive analysis of the microbial community structure and EPS proteins and polysaccharide profiles of the mixed liquor and cake layer was carried out throughout both operation periods. The results of this study showed that the imposition of a shorter SRT led to a shift in the dominant bacterial populations. The mixed liquor and cake layer communities were very different, with Actinomycetales order standing out in the cake layer at SRT of 20 days. Overall, higher EPS concentrations (particularly proteins) were found at this SRT. Furthermore, EPS profiles were clearly affected by the SRT: it was possible to correlate a group of soluble EPS proteins with the SRT of 60 days, and a lower sludge age led to a lower diversity of polysaccharide sugar monomers, with an increase of glucose and galactose in the cake layer. This study improves our knowledge regarding the molecular reasons for fouling, which may contribute to improve MBR design and operation.
IBET-Instituto de Biologia Experimental e Tecnológica, Apartado12, 2781-901, Oeiras, Portugal.|Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal.
Ana F
AF
Silva
UCIBIO-REQUIMTE, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
Sílvia
S
Antunes
Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark.
Aaron
A
Saunders
UCIBIO-REQUIMTE, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
Filomena
F
Freitas
IBET-Instituto de Biologia Experimental e Tecnológica, Apartado12, 2781-901, Oeiras, Portugal.|Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal.
Anabela
A
Vieira
LAQV, REQUIMTE, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
Claudia F
CF
Galinha
Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark.
Per H
PH
Nielsen
IBET-Instituto de Biologia Experimental e Tecnológica, Apartado12, 2781-901, Oeiras, Portugal. tcrespo@itqb.unl.pt.|Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal. tcrespo@itqb.unl.pt.
Maria Teresa
MT
Barreto Crespo
UCIBIO-REQUIMTE, Chemistry Department, FCT, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
Gilda
G
Carvalho
D001426:Bacterial Proteins / Q000032:analysis*; D019149:Bioreactors / Q000382:microbiology*; D058448:Biota; D008566:Membranes / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000032:analysis*; D013997:Time Factors; D062065:Wastewater; D018508:Water Purification / Q000379:methods
D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D062065:Wastewater
Extracellular polymeric substances; Membrane bioreactor; Microbial community; Polysaccharide; Protein; Sludge retention time