Precipitation refers to the formation of a solid from solutes in a supersaturated solution under ... more Precipitation refers to the formation of a solid from solutes in a supersaturated solution under certain conditions (Myerson, 1993). There are a range of precipitation processes, including crystallisation, ion complexing, and ion-complex adsorption. Particularly, the latter may result in variable reaction stoichiometry, and is not effectively represented by a fixed stoichiometry approach as in the first part of this chapter. An alternative approach for hydroxy-ion and aluminium phosphorus precipitation is discussed further in Section 3.22. The process of precipitation itself may have multiple stages as further discussed below. Reactants for precipitation are generally ionic solutes, but non-ionic compounds can also form precipitates, commonly through dehydration, for example, Precipitation is widespread in the water cycle, with common precipitating cations being calcium (as Ca 2+ ), magnesium (as Mg 2+ ), aluminium (as Al 3+ ), iron (as Fe 2+ and Fe 3+ ), as well as ammonium (NH 4 + ) being involved in multi-cation minerals such as struvite (NH 4 MgPO 4 •6H 2 O). Common precipitating anions are carbonates (CO 3 2-), phosphates (PO 4 3-), sulfates (SO 4 2-), and sulfides (S 2-), and hydroxides (OH -) particularly for multi-anion precipitates or at high pH (e.g., Ca(OH) 2 ). Precipitates are commonly chemically hydrated (note struvite above) meaning that water forms a part of the precipitate chemical structure. Precipitates may be amorphous or crystalline. Amorphous precipitates lack regular crystalline structure, generally form rapidly, and have relatively low stability, meaning they will dissolve to their respective solutes rapidly under appropriate conditions. Crystalline precipitates have a crystal structure
Investigate PAO-GAO Competition under Extended Anaerobic Conditions as in Side-stream Enhanced Biological Phosphorus Removal (S2EBPR) using Agent-based Model
Proceedings of the Water Environment Federation, 2018
International Journal of Environmental Research, 2016
The stoichiometric parameter namely “Yield Coefficient” associated with growth of certain organis... more The stoichiometric parameter namely “Yield Coefficient” associated with growth of certain organism can be determined by direct measurement and/or calculated indirectly. The focus of this paper was on the anoxic yield of heterotrophic organisms using ethanol as an external carbon source during the denitrification process. In the literature, it was observed that yield coefficients can vary for the same substrate, which can be referred to the relative acclimation to the substrate. The aim of this study was to evaluate the yields determined through various catabolic and anabolic estimations. This paper presents ten different yield coefficient calculation methods under anoxic conditions in a sequencing batch reactor using ethanol as an external substrate. The range of anoxic yield using different calculation methods was between 0.423±0.014 to 0.512±0.021 mgCOD/mgCOD at 20C. It was concluded that there was no statistically significant difference between the yield values calculated from t...
Proceedings of the Water Environment Federation, 2008
Parametric models used in simulation software for the design of wastewater treatment plants invol... more Parametric models used in simulation software for the design of wastewater treatment plants involve a number of processes and state variables that can be best represented in a matrix format (e.g. ASM1, ASM2D, ASM3, General ASDM). These models often use different symbols for identical variables and some models are becoming increasingly complex making it difficult to visualize the relationships between the various processes. A standardized notation is first proposed for the major current parametric models which is then used to draw schematic representations of these models. These schematics should constitute useful learning tools, that should facilitate comparisons between various models and provide a better appreciation of the potential and limitations of each model to ensure a better use of activated sludge models by design engineers.
The Vesilind settling velocity function forms the basis of flux theory used both in state point a... more The Vesilind settling velocity function forms the basis of flux theory used both in state point analysis (for design and capacity rating) and one-dimensional dynamic models (for dynamic process modelling). This paper proposes new methods to address known shortcomings of these methods, based on an extensive set of batch settling tests conducted at different scales. The experimental method to determine the Vesilind parameters from a series of bench scale settling tests is reviewed. It is confirmed that settling cylinders must be slowly stirred in order to represent settling performance of full scale plants for the whole range of solids concentrations. Two new methods to extract the Vesilind parameters from settling test series are proposed and tested against the traditional manual method. Finally, the same data set is used to propose an extension to one-dimensional (1-D) dynamic settler models to account for compression settling. Using the modified empirical function, the model is able to describe the batch settling interface independently of the number of layers.
The objective of this paper is to identify the importance of kinetic parameters relating to the u... more The objective of this paper is to identify the importance of kinetic parameters relating to the utilization of nitrite when nitrification and denitrification are modeled as two-step processes. This is an important issue relating to modeling for design and in operation of plants achieving low effluent TN concentrations. A case study using a calibrated model of a full scale plant achieving low effluent TN is used to demonstrate the impacts of key modeling parameters on effluent predictions. The results also demonstrate the importance of full scale plant calibration based on historical data and detailed plant sampling and profiling.
Modelling biological phosphorus removal from a cheese factory effluent by an SBR
Water Science and Technology, 2001
A mathematical model, named A3DX, based on ASM3(A3) for C and N removal, on the bio-P metabolic m... more A mathematical model, named A3DX, based on ASM3(A3) for C and N removal, on the bio-P metabolic model of the Technological University of Delft (D), and on extra processes (X) for chemical and biological phosphorus removal, was developed and used to simulate the treatment of a fermented cheese factory effluent by a sequencing batch reactor (SBR). Experimental data obtained from a pilot-scale SBR were used to calibrate the model. The model calibration was performed by changing a minimal number (four) of default values for parameters, and by introducing a Monod function to account for magnesium limitation. This study suggests that the value of stoichiometric and kinetic model parameters determined with municipal effluents or enriched bio-P cultures can be reasonably used with some agro-industrial effluents with minimal parameter adjustment for calibration.
A comparative analysis of different approaches for integrated WWTP modelling
Water Science and Technology, 2009
In this paper a comparative analysis of the most important approaches for integrated WWTP modelli... more In this paper a comparative analysis of the most important approaches for integrated WWTP modelling is presented. After an introductory presentation of the most important drawbacks and challenges for plant wide modelling, the fundamentals of three different approaches to construct integrated models are presented: “Interfaces” “Standard Supermodel” and “Tailored Supermodel”. Afterwards, a comparative analysis of these approaches from different points of view (difficulties for the model end user, characterization of the process in the plant, flexibility or adaptability for each case of study, simulation platform requirements and computational costs) is carried out. From this comparison, some important conclusions about the suitability of each alternative depending on the simulation case study are extracted.
Estimating (combinations of) activated sludge model no. 1 parameters and components by respirometry
Water Science and Technology, 1999
... 1 PARAMETERS AND COMPONENTS BY RESPIROMETRY Peter A. Vanrolleghem*, Henri Spanjers**, Britta ... more ... 1 PARAMETERS AND COMPONENTS BY RESPIROMETRY Peter A. Vanrolleghem*, Henri Spanjers**, Britta Petersen*'*** Philippe Ginestetf and Imre ... Task Group on Mathematical Modelling for Design and Operation of Biological Wastewater Treatment Processes (Henze et al ...
Applications of Mobile Carrier Biofilm Modelling for Wastewater Treatment Processes
One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofil... more One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofilm reactor design. Limitations using mechanistic biofilm models for engineering design do not rely on improved biofilm models, but rely on improved biofilm reactor models. This is important when considering that biofilm reactors containing submerged, free-moving biofilm carriers are the most widely applied biofilm system(s) for municipal wastewater treatment. This paper presents a new biofilm reactor model that considers the impact of submerged free-moving biofilm carrier (Xcarrier) movement on system performance. The model accounts for a hydrodynamic condition characterized as plug flow with back mixing (to model axial dispersion). The relevance of this new biofilm reactor model to engineering situations is evaluated by applying it to relevant scenarios and comparing model results.
Physiological adaptation as it occurs in bacterial cells at variable environmental conditions inf... more Physiological adaptation as it occurs in bacterial cells at variable environmental conditions influences characteristic properties of growth kinetics significantly. However, physiological adaptation to growth related parameters in activated sludge modelling is not yet recognised. Consequently these parameters are regarded to be constant. To investigate physiological adaptation in activated sludge the endogenous respiration in an aerobic degradation batch experiment and simultaneous to that the maximum possible respiration in an aerobic growth batch experiment was measured. The activated sludge samples were taken from full scale wastewater treatment plants with different sludge retention times (SRTs). It could be shown that the low SRT sludge adapts by growth optimisation (high maximum growth rate and high decay rate) to its particular environment where a high SRT sludge adapts by survival optimization (low maximum growth rate and low decay rate). Thereby, both the maximum specific growth rate and the decay rate vary in the same pattern and are strongly correlated to each other. To describe the physiological state of mixed cultures like activated sludge quantitatively a physiological state factor (PSF) is proposed as the ratio of the maximum specific growth rate and the decay rate. The PSF can be expressed as an exponential function with respect to the SRT.
Estimating (combinations of) Activated Sludge Model No. 1 parameters and components by respirometry
Water Science and Technology, 1999
... 1 PARAMETERS AND COMPONENTS BY RESPIROMETRY Peter A. Vanrolleghem*, Henri Spanjers**, Britta ... more ... 1 PARAMETERS AND COMPONENTS BY RESPIROMETRY Peter A. Vanrolleghem*, Henri Spanjers**, Britta Petersen*'*** Philippe Ginestetf and Imre ... Task Group on Mathematical Modelling for Design and Operation of Biological Wastewater Treatment Processes (Henze et al ...
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Papers by Imre Takács