Development of mechanistically based model for simulating soluble microbial products generation in an aerated/non-aerated SBR.
ABSTRACT Soluble microbial products (SMPs) are considered as the main organic components in wastewater treatment plant effluent from biological wastewater treatment systems. To investigate and explore SMP metabolism pathway for further treatment and control, two innovative mechanistically based activated sludge models were developed by extension of activated sludge model no.3 (ASM3). One was the model by combining SMP formation and degradation (ASM3-SMP model) processes with ASM3, and the other by combining both SMP and simultaneous substrate storage and growth (SSSG) mechanisms with ASM3 (SSSG-ASM3-SMP model). The detailed schematic modification and process supplements were introduced for comprehensively understanding all the mechanisms involved in the activated sludge process. The evaluations of these two models were demonstrated by a laboratory-scale sequencing batch reactor (SBR) operated under aerated/non-aerated conditions. The simulated and measured results indicated that SMP comprised about 83% of total soluble chemical oxygen demand (SCOD) in which biomass-associated products (BAPs) were predominant compared with utilization-associated products (UAPs). It also elucidated that there should be a minimum SMP value as the reactive time increases continuously and this conclusion could be used to optimize effluent SCOD in activated sludge processes. The comparative results among ASM3, ASM3-SMP and SSSG-ASM3-SMP models and the experimental measurements (SCOD, ammonia and nitrate nitrogen) showed clearly the best agreement with SSSG-ASM3-SMP simulation values (R = 0.993), strongly suggesting that both SMP formation and degradation and SSSG mechanisms are necessary in biologically activated sludge modeling for municipal wastewater treatment.
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ABSTRACT: The relationship between soluble microbial products (SMPs) and extracellular polymeric substances is described, and the characteristics of SMPs in the biological wastewater treatment process, including molecular weight distribution, metal-chelating property, biodegradability, biotoxicity, and membrane fouling, are investigated. The SMPs produced by autotrophs are degradable and utilizable for heterotrophs, thereby confirming the biodegradation of SMPs. Soluble microbial product models are designed through three approaches: establishment of SMP kinetic models or combination with Monod equations, incorporation of SMP generation and degradation into the unified theory raised by Laspidou and Rittmann (2002a), and introduction of the concept of SMP into activated sludge models. The effects of process parameters on SMP concentration are elaborated, based on the optimum biological treatment process operating parameters that can effectively minimize SMP production. The progress of SMP research in water biotreatment systems is presented, and suggestions for future studies are made.Water Environment Research 03/2014; 86(3):223-31. DOI:10.2175/106143013X13807328849413