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Choubert J.-M.,IRSTEA | Rieger L.,EnviroSim Associates Ltd | Shaw A.,Black and Veatch Corporation | Copp J.,Primodal Inc. | And 7 more authors.
Water Science and Technology | Year: 2013

Increasingly stringent effluent limits and an expanding scope of model system boundaries beyond activated sludge has led to new modelling objectives and consequently to new and often more detailed modelling concepts. Nearly three decades after the publication of Activated Sludge Model No1 (ASM1), the authors believe it is time to re-evaluate wastewater characterisation procedures and targets. The present position paper gives a brief overview of state-of-the-art methods and discusses newly developed measurement techniques on a conceptual level. Potential future paths are presented including on-line instrumentation, promising measuring techniques, and mathematical solutions to fractionation problems. This is accompanied by a discussion on standardisation needs to increase modelling efficiency in our industry. © IWA Publishing 2013.

Alex J.,ifak E.V. Magdeburg | Ronner-Holm S.G.E.,LimnoTec Abwasseranlagen GmbH | Hunze M.,Flow Concept GmbH | Holm N.C.,LimnoTec Abwasseranlagen GmbH
Water Science and Technology | Year: 2011

A sequencing batch reactor (SBR) model was developed consisting of six continuous stirred tank reactors which describe the hydraulic flow patterns occurring in different SBR phases. The model was developed using the results of computational fluid dynamics (CFD) simulation studies of an SBR reactor under a selection of dynamic operational phases. Based on the CFD results, the model structure was refined and a simplified 'driver' model to allow one to mimic the flow pattern driven by the external operational conditions (influent, aeration, mixing) was derived. The resulting model allows the modeling of biological processes, settlement and hydraulic conditions of cylindrical SBRs. © IWA Publishing 2011.

Wett B.,ARAconsult | Jimenez J.A.,Brown and Caldwell | Takacs I.,EnviroSim Europe | Murthy S.,DCWASA | And 3 more authors.
Water Science and Technology | Year: 2011

Models for engineering design of nitrifying systems use one ammonia oxidizer biomass (AOB) state variable. A simple extension using two AOB populations allows a more accurate prediction of nitrification systems at switching process environments. These two AOB subpopulations are characterized by two different sets of kinetic parameters. Selection pressure and competition between the two functional AOB populations are determined by process conditions as demonstrated by three case studies: Case study I describes dynamics of two AOB populations showing different temperature sensitivities (modified Arrhenius term on growth and decay) when bioaugmented from the warm sidestream treatment environment to the cold mainstream and vice-versa. Case study II investigates competition between fast growing μ-strategists and k-strategists adjusted to low ammonia levels depending on the internal mixed liquor recycle rate (IMLR). Case study III shows that AOB transferred from the waste activated sludge of an SBR to the parallel continuous flow system with different decay kinetics can overgrow or coexist with the original population. © IWA Publishing 2011.

Ronner-Holm S.G.E.,LimnoTec Abwasseranlagen GmbH | Zak A.,Lublin University of Technology | Holm N.C.,LimnoTec Abwasseranlagen GmbH
Water Science and Technology | Year: 2012

Simulation studies for a full-scale anaerobic unit of a wastewater treatment plant (WWTP) were performed using the anaerobic digestion model no. 1 (ADM1). The anaerobic full-scale plant consists of one mesophilic and one thermophilic digester, operated in an anaerobic sequential batch reactor (ASBR) mode, and sludge enrichment reactors (SER) for each digester. The digesters are fed with a mixture of vegetable waste and process wastewater from the food factory. Characteristics such as COD total, N total and NH 4-N concentrations in the influent and effluent of the digester and SERs were measured and used for input fractionation. Parameters such as level, pH, biogas amount and composition in the digester were measured online and used for calibration. For simulation studies, different temperatures and operation modes with varying chemical oxygen demand (COD) input loads corresponding to feedstocks such as fruits, vegetables and grain were analysed and compared. Higher gas production and digestion efficiency in the thermophilic reactor and in shorter cycles were found and confirmed at full scale. Serial operation mode increased the gas production, but pH inhibition occurred earlier. Feeding only biosolids into digester I and the effluent of digester I together with process water into digester II further improved gas production in serial operation mode. © IWA Publishing 2012.

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