High loaded MBRs for organic matter recovery from sewage: Effect of solids retention time on bioflocculation and on the role of extracellular polymers

• Published in: Water research (Oxford) Vol. 56; pp. 258 - 266
• Main Authors: Faust, L., Temmink, H., Zwijnenburg, A., Kemperman, A.J.B., Rijnaarts, H.H.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2014; Elsevier
• Subjects: Activated sludge; activated-sludge process; Afvalwaterbehandeling; Applied sciences; Bacteria - metabolism; biofilms; Bioflocculation; Biological and medical sciences; Biological treatment of waters; Biopolymers; Bioreactors; Biotechnology; constituents; Environment and pollution; EPS; Exact sciences and technology; Extracellular polymeric substances; extraction; Fatty acids; Flocculating; Flocculation; Fouling; Fundamental and applied biological sciences. Psychology; General purification processes; improved energy recovery; Industrial applications and implications. Economical aspects; Membrane bioreactor; membranen; Membranes; Membranes, Artificial; Methane; microbial community; municipal waste-water; organic matter; organische stof; Pollution; Recovery; Sewage; Sewage - chemistry; submerged membrane bioreactor; substances eps; surface-properties; Waste Disposal, Fluid - methods; Waste Water Treatment; Wastewaters; water treatment; Water treatment and pollution; waterzuivering; Membrane bioreactor; Activated sludge; Extracellular polymeric substances; Bioflocculation; Water treatment; Organic matter; Natural polymer; Aerobe; Retention time; Sustainable development; Extracellular; Biological purification; Membrane reactor; Bioreactor; Flocculation; Biopolymer; Oside polymer; Urban waste water; Waste water purification; Polysaccharide
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2014.03.006

High loaded MBRs (HL-MBR) can concentrate sewage organic matter by aerobic bioflocculation for subsequent anaerobic conversion to methane or volatile fatty acids. In the range of very short solid retention times (SRT), the effect of SRT on bioflocculation and EPS production in HL-MBR was investigated. This short SRT range was selected to find an optimum SRT maximising recovery of organics by aerobic bioflocculation and minimizing losses of organics by aerobic mineralization. Bioflocculation was studied in five HL-MBRs operated at SRTs of 0.125, 0.25, 0.5, 1 and 5 d. The extent of flocculation, defined as the fraction of suspended COD in the concentrate, increased from 59% at an SRT of 0.125 d to 98% at an SRT of 5 d. The loss of sewage organic matter by biological oxidation was 1, 2, 4, 11 and 32% at SRT of 0.125–5 d. An SRT of 0.5–1 d gave best combination of bioflocculation and organic matter recovery. Bound extracellular polymeric substances (EPS) concentrations, in particular EPS-protein concentrations, increased when the SRT was prolonged from 0.125 to 1 d. This suggests that these EPS-proteins govern the bioflocculation process. A redistribution took place from free (supernatant) EPS to bound (floc associated) EPS when the SRT was prolonged from 0.125 to 1 d, further supporting the fact that the EPS play a dominant role in the flocculation process. Membrane fouling was most severe at the shortest SRTs of 0.125 d. No positive correlation was detected between the concentration of free EPS and membrane fouling, but the concentration of submicron (45–450 nm) particles proved to be a good indicator for this fouling. [Display omitted] •We examined bioflocculation of wastewater in HL-MBRs at very short SRTs and HRTs.•We studied EPS concentration at various short SRTs in relation to bioflocculation.•Bioflocculation and EPS concentration increased when SRT was prolonged to 1 d.•Amount of COD mineralized increased from 1 to 32% when SRT was prolonged (0.125–5 d).•Fouling was reduced as bioflocculation was improved.