A review of soluble microbial products (SMP) in wastewater treatment systems

• Published in: Water Research Vol. 33; no. 14; pp. 3063 - 3082
• Main Authors: Barker, Duncan J., Stuckey, David C.
• Format: Book Review Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1999; Elsevier Science
• Subjects: Applied sciences; Biochemical oxygen demand; biodegradability; Biodegradation; Biological and medical sciences; Biological treatment of waters; Biological water treatment; Biomass; Biotechnology; characterisation; chelating; effluent; Effluent treatment; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Industrial applications and implications. Economical aspects; Metabolism; Molecular weight distribution; Pollution; process performance; Reaction kinetics; Sewage sludge; soluble microbial products (SMP); Toxicity; Wastewaters; Water treatment and pollution; United Kingdom; toxicity; PACT, powdered activated carbon treatment; HRT, hydraulic retention time; UF, ultrafiltration; BMP, biochemical methane potential; SON, soluble organic nitrogen; TOC, total organic carbon; OLR, organic loading rate; soluble microbial products (SMP); SRP, soluble residual products; PAC, powdered activated carbon; COD, chemical oxygen demand; CSTR, continuously stirred tank reactor; chelating; ABR, anaerobic baffled reactor; UAP, utilisation associated products; biodegradability; MW, molecular weight; MLVSS, mixed liquor volatile suspended solids; SMP, soluble microbial products; VSS, volatile suspended solids; BAP, biomass associated products; ECP, extracellular polymers; process performance; molecular weight distribution; GPC, gel permeation chromatography; GAC, granular activated carbon; SOC, soluble organic carbon; UASB, upflow anaerobic sludge blanket; AMW, apparent molecular weight; effluent; characterisation; MLSS, mixed liquor suspended solids; SRT, sludge retention time; BOD, biochemical oxygen demand; SBR, sequencing batch reactor; THM, trihalomethane; Molecular weight distribution; Biodegradability; Reaction product; Soluble compound; Review; Biomass; Waste water purification; Organic compounds; Biological purification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(99)00022-6

A review concerning the characterisation, production, modelling, significance and implications of soluble microbial products (SMP) in wastewater treatment is presented. The precise definition of SMP is open to debate, but is currently regarded as “the pool of organic compounds that are released into solution from substrate metabolism (usually with biomass growth) and biomass decay”, although for anaerobic systems volatile fatty acids are not included as SMP. Some of the SMP have been identified as humic and fulvic acids, polysaccharides, proteins, nucleic acids, organic acids, amino acids, antibiotics, steroids, exocellular enzymes, siderophores, structural components of cells and products of energy metabolism. Crucially, SMP have been found to comprise the majority of soluble organic material in the effluents from biological treatment processes and their presence is, therefore, of particular interest in terms of achieving discharge consent levels for BOD and COD. SMP also exhibit several characteristics, such as toxicity and metal chelating properties, which effect the performance of the treatment system, and their presence has also been shown to adversely affect the kinetic activity and the flocculating and settling properties of sludge. This review outlines some important discoveries with regard to the MW distribution, biodegradability and treatability of SMP and also the effect of process parameters on their production. It also summarises the attempts at incorporating SMP formation into the modelling of wastewater treatment. However, it concludes that the knowledge regarding SMP is far from complete and that much work is still required to fully understand their contribution to the treatment process; some of these future research areas are then outlined.