M. Henze - Academia.edu (original) (raw)

Papers by M. Henze

Water science and technology : a journal of the International Association on Water Pollution Research, 2004

This paper presents the existing philosophy, approach, criteria and delivery of environmental eng... more This paper presents the existing philosophy, approach, criteria and delivery of environmental engineering education (E3) for developing countries. In general, environmental engineering is being taught in almost all major universities in developing countries, mostly under civil engineering degree programmes. There is an urgent need to address specific inputs that are particularly important for developing countries with respect to the reality of urbanisation and industrialisation. The main component of E3 in the near future will remain on basic sanitation in most developing countries, with special emphasis on the consumer-demand approach. In order to substantially overcome environmental problems in developing countries, E3 should include integrated urban water management, sustainable sanitation, appropriate technology, cleaner production, wastewater minimisation and financial framework.

An experimental procedure was developed for the respirometric determination of bacterial storage ... more An experimental procedure was developed for the respirometric determination of bacterial storage yield as defined in the Activated Sludge Model No. 3. The proposed approach is based on the oxygen utilization rate ͑OUR͒ profile obtained from a batch test and correlates the area under the OUR curve to the amount of oxygen associated with substrate storage. Model simulation was used to evaluate the procedure for different initial experimental conditions. The procedure was tested on acetate. The same storage yield value of 0.76 gCOD/gCOD was calculated for two experiments, starting with different F/M ratios of 0.12 and 0.64 gCOD/g cellCOD.

Environmental Modelling & Software, 2004

This review paper focuses on modelling of wastewater treatment plants (WWTP). White-box modelling... more This review paper focuses on modelling of wastewater treatment plants (WWTP). White-box modelling is widely applied in this field, with learning, design and process optimisation as the main applications. The introduction of the ASM model family by the IWA task group was of great importance, providing researchers and practitioners with a standardised set of basis models. This paper introduces the nowadays most frequently used white-box models for description of biological nitrogen and phosphorus removal activated sludge processes. These models are mainly applicable to municipal wastewater systems, but can be adapted easily to specific situations such as the presence of industrial wastewater. Some of the main model assumptions are highlighted, and their implications for practical model application are discussed. A step-wise procedure leads from the model purpose definition to a calibrated WWTP model. Important steps in the procedure are: model purpose definition, model selection, data collection, data reconciliation, calibration of the model parameters and model unfalsification. The model purpose, defined at the beginning of the procedure, influences the model selection, the data collection and the model calibration. In the model calibration a process engineering approach, i.e. based on understanding of the process and the model structure, is needed. A calibrated WWTP model, the result of an iterative procedure, can usually be obtained by only modifying few model parameters, using the default parameter sets as a starting point. Black-box, stochastic grey-box and hybrid models are useful in WWTP applications for prediction of the influent load, for estimation of biomass activities and effluent quality parameters. These modelling methodologies thus complement the process knowledge included in white-box models with predictions based on data in areas where the white-box model assumptions are not valid or where white-box models do not provide accurate predictions. Artificial intelligence (AI) covers a large spectrum of methods, and many of them have been applied in applications related to WWTPs. AI methodologies and white-box models can interact in many ways; supervisory control systems for WWTPs are one evident application. Modular agent-based systems combining several AI and modelling methods provide a great potential. In these systems, AI methods on one hand can maximise the knowledge extracted from data and operator experience, and subsequently apply this knowledge to improve WWTP control. White-box models on the other hand allow evaluating scenarios based on the available process knowledge about the WWTP. A white-box model calibration tool, an AI based WWTP design tool and a knowledge representation tool in the WWTP domain are other potential applications where fruitful interactions between AI methods and white-box models could be developed. 

The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et ... more The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et al. and Reichert et al. is comprehensive. Shanahan et al. introduced a six-step decision procedure to select the necessary model features for a certain application. This paper specifically addresses one of these steps, i.e. the selection of submodels of the comprehensive biochemical conversion model introduced in Reichert et al. Specific conditions for inclusion of one or the other conversion process or model component are introduced, as are some general rules that can support the selection. Examples of simplified models are presented.

Water science and technology : a journal of the International Association on Water Pollution Research, 2001

In this paper, biochemical process equations are presented as a basis for water quality modelling... more In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aerobic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes. This paper is part of a series of three papers. In the first paper, the general modelling approach is described; in the present paper, the biochemical process equations of a complex model are presented; and in the third paper, recommendations are given for the selection of a reasonable submodel for a specific application.

Water Science and Technology, 1998

River water quality models are used extensively in research as well as in the design and assessme... more River water quality models are used extensively in research as well as in the design and assessment of water quality management measures. The application of mathematical models for that purpose dates back to the initial studies of oxygen depletion due to organic waste pollution. Since then, models have been constantly refined and updated to meet new and emerging problems of surface water pollution, such as eutrophication, acute and chronic toxicity, etc. In order to handle the complex interactions caused by the increased influence of human activities in rivers it is today mandatory to couple river water quality models with models describing emissions from the drainage and sewerage system (such as the IAWQ Activated Sludge model No.1). In this paper-which is the first of a three-part series by the IAWQ Task Group on River Water Quality Modellingthe state of the art is summarized with the above aim in mind. Special attention is given here to the modelling of conversion processes but also the methods and tools to work with the models, i.e. parameter estimation, measurement campaign design, and simulation software, are discussed.

Water Research, 1998

Acharacteristic of the biological phosphorus removal process is the interaction between different... more Acharacteristic of the biological phosphorus removal process is the interaction between different intracdhrlar components. Therefore, an understanding of the effects of the intracellular components on biologicalphosphorus removal is essential for the practical application of the process. In this study, the stoichiometryof poly-hydroxybutyrate(PHB) to P-uptake and the kinetics of uptake of ortho-phosphatein relation to PHB were investigatedunder aerobic and substrate limitingconditions in batch experiments with activated sludge from a biological phosphorus removal process. The stoichiometryof PHB to P-uptake was investigatedby determination of the degradation rate of PHB under aerobic conditions in the presence and absence of ortho-phosphate in the bulk liquid. The degradation of PHB as a function of time was described by a first-order equation. The presence of ortho-phosphate increased the rate of PHB degradation significantly,confirming that the uptake of ortho-phosphate directly required PHB. The fraction of PHB usedforuptakeof ortho-phosphate from thebulkliquidwasestimatedto be300/.. Furthermore, batchexperiments confirmed that theuptakerate of ortho-phosphate underaerobicconditions washighlydependent on theconcentration of PHBin the biomass.The observeduptakerate of ortho-phosphate as a functionof the PHB concentration was mathematicallydescribed bya Monodequation. Themaximum uptakerateof the sludgewasestimated to be 14(mg-P/g-VSS)/h. The obtainedresultsadd to the understanding of the mechanisms of the biological phosphorus removal processunderthestressconditions withlimitingsubstratesupplies present in thefull-scale wastewater treatmentprocess. Furthermore, theresultsindicatethat controlstrategies to stabilisethe processshouldfocuson a maintenance and optimalutilisationof PHB.@ 1998Ekevier ScienceLtd. All rightsreserved

Water Science and Technology, 1998

This paper is the third of a three-part series summarizing the background to and objectives of th... more This paper is the third of a three-part series summarizing the background to and objectives of the activity of the IAWQ Task Group on River Water Quality Modelling (RWQM). On the basis of the two other papers and a comparison between the best known state of the art river model, QUAL2, and the IAWQ Activated Sludge Model (ASM) No. 1, the Task Group proposes to develop improved conversion models for inclusion in a river water quality model. The model should describe the cycling of oxygen, nitrogen, and phosphorus in both water and sediment, and should be compatible with the ASM to support the development of integrated emission reduction strategies. The model should be particularly well suited to handle problems characterized by significant temporal and spatial influences (e.g. CSOs and NPSs). It should serve for research, education, improved communication, knowledge transfer, regulatory applications such as catchment planning, and improved data collection. Anticipated results of the Task Group effort include (i) standardized conversion sub-models; (ii) a decision support tool to guide model construction and usage; and (iii) case study applications. The model development, which is not intended to result in a software product, is intended to be an open-ended and flexible process to encourage the participation of interested professionals.

Water Science and Technology, 1998

The U.S. EPA QUAL2 model is currently the standard for river water quality modelling. While QUAL2... more The U.S. EPA QUAL2 model is currently the standard for river water quality modelling. While QUAL2 is adequate for the regulatory situation for which it was developed (the U.S. wasteload allocation process), there is a need for a more comprehensive framework for research and teaching. Moreover, QUAL2 and similar models do not address a number of practical problems such as stormwater flow events, nonpoint source pollution, and transient streamflow. Limitations in model formulation affect the ability to close mass balances, to represent sessile bacteria and other benthic processes, and to achieve robust model calibration. Mass balance problems aris e from failure to account for mass in the sediment as well as in the water column and due to the fundamental imprecision of BOD as a state variable.

Microbial community structures were assessed in a two-stage anaerobic digestion system treating f... more Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was ...

The new River Water Quality Model no.1 introduced in the two accompanying papers by and is compre... more The new River Water Quality Model no.1 introduced in the two accompanying papers by and is comprehensive. Shanahan et al. introduced a six-step decision procedure to select the necessary model features for a certain application. This paper specifically addresses one of these steps, i.e. the selection of submodels of the comprehensive biochemical conversion model introduced in Reichert et al. (2000). Specific conditions for inclusion of one or the other conversion process or model component are introduced, as are some general rules that can support the selection. Examples of simplified models are presented.

ABSTRACT Successful river water quality modelling requires the specifi cation of an appropriate m... more ABSTRACT Successful river water quality modelling requires the specifi cation of an appropriate model,structure and process formulation. Both must be related to the compartment,stru cture of running water ecosystems,including their longitudinal, vertical, and lateral zonation patterns. Furtherm ore, the temporal variability of abiotic boundary conditions may be important and must be incorporated by an appropria te choice of model parameters.

Water science and technology : a journal of the International Association on Water Pollution Research, 2004

This paper presents the existing philosophy, approach, criteria and delivery of environmental eng... more This paper presents the existing philosophy, approach, criteria and delivery of environmental engineering education (E3) for developing countries. In general, environmental engineering is being taught in almost all major universities in developing countries, mostly under civil engineering degree programmes. There is an urgent need to address specific inputs that are particularly important for developing countries with respect to the reality of urbanisation and industrialisation. The main component of E3 in the near future will remain on basic sanitation in most developing countries, with special emphasis on the consumer-demand approach. In order to substantially overcome environmental problems in developing countries, E3 should include integrated urban water management, sustainable sanitation, appropriate technology, cleaner production, wastewater minimisation and financial framework.

An experimental procedure was developed for the respirometric determination of bacterial storage ... more An experimental procedure was developed for the respirometric determination of bacterial storage yield as defined in the Activated Sludge Model No. 3. The proposed approach is based on the oxygen utilization rate ͑OUR͒ profile obtained from a batch test and correlates the area under the OUR curve to the amount of oxygen associated with substrate storage. Model simulation was used to evaluate the procedure for different initial experimental conditions. The procedure was tested on acetate. The same storage yield value of 0.76 gCOD/gCOD was calculated for two experiments, starting with different F/M ratios of 0.12 and 0.64 gCOD/g cellCOD.

Environmental Modelling & Software, 2004

This review paper focuses on modelling of wastewater treatment plants (WWTP). White-box modelling... more This review paper focuses on modelling of wastewater treatment plants (WWTP). White-box modelling is widely applied in this field, with learning, design and process optimisation as the main applications. The introduction of the ASM model family by the IWA task group was of great importance, providing researchers and practitioners with a standardised set of basis models. This paper introduces the nowadays most frequently used white-box models for description of biological nitrogen and phosphorus removal activated sludge processes. These models are mainly applicable to municipal wastewater systems, but can be adapted easily to specific situations such as the presence of industrial wastewater. Some of the main model assumptions are highlighted, and their implications for practical model application are discussed. A step-wise procedure leads from the model purpose definition to a calibrated WWTP model. Important steps in the procedure are: model purpose definition, model selection, data collection, data reconciliation, calibration of the model parameters and model unfalsification. The model purpose, defined at the beginning of the procedure, influences the model selection, the data collection and the model calibration. In the model calibration a process engineering approach, i.e. based on understanding of the process and the model structure, is needed. A calibrated WWTP model, the result of an iterative procedure, can usually be obtained by only modifying few model parameters, using the default parameter sets as a starting point. Black-box, stochastic grey-box and hybrid models are useful in WWTP applications for prediction of the influent load, for estimation of biomass activities and effluent quality parameters. These modelling methodologies thus complement the process knowledge included in white-box models with predictions based on data in areas where the white-box model assumptions are not valid or where white-box models do not provide accurate predictions. Artificial intelligence (AI) covers a large spectrum of methods, and many of them have been applied in applications related to WWTPs. AI methodologies and white-box models can interact in many ways; supervisory control systems for WWTPs are one evident application. Modular agent-based systems combining several AI and modelling methods provide a great potential. In these systems, AI methods on one hand can maximise the knowledge extracted from data and operator experience, and subsequently apply this knowledge to improve WWTP control. White-box models on the other hand allow evaluating scenarios based on the available process knowledge about the WWTP. A white-box model calibration tool, an AI based WWTP design tool and a knowledge representation tool in the WWTP domain are other potential applications where fruitful interactions between AI methods and white-box models could be developed. 

The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et ... more The new River Water Quality Model no. 1 introduced in the two accompanying papers by Shanahan et al. and Reichert et al. is comprehensive. Shanahan et al. introduced a six-step decision procedure to select the necessary model features for a certain application. This paper specifically addresses one of these steps, i.e. the selection of submodels of the comprehensive biochemical conversion model introduced in Reichert et al. Specific conditions for inclusion of one or the other conversion process or model component are introduced, as are some general rules that can support the selection. Examples of simplified models are presented.

Water science and technology : a journal of the International Association on Water Pollution Research, 2001

In this paper, biochemical process equations are presented as a basis for water quality modelling... more In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aerobic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes. This paper is part of a series of three papers. In the first paper, the general modelling approach is described; in the present paper, the biochemical process equations of a complex model are presented; and in the third paper, recommendations are given for the selection of a reasonable submodel for a specific application.

Water Science and Technology, 1998

River water quality models are used extensively in research as well as in the design and assessme... more River water quality models are used extensively in research as well as in the design and assessment of water quality management measures. The application of mathematical models for that purpose dates back to the initial studies of oxygen depletion due to organic waste pollution. Since then, models have been constantly refined and updated to meet new and emerging problems of surface water pollution, such as eutrophication, acute and chronic toxicity, etc. In order to handle the complex interactions caused by the increased influence of human activities in rivers it is today mandatory to couple river water quality models with models describing emissions from the drainage and sewerage system (such as the IAWQ Activated Sludge model No.1). In this paper-which is the first of a three-part series by the IAWQ Task Group on River Water Quality Modellingthe state of the art is summarized with the above aim in mind. Special attention is given here to the modelling of conversion processes but also the methods and tools to work with the models, i.e. parameter estimation, measurement campaign design, and simulation software, are discussed.

Water Research, 1998

Acharacteristic of the biological phosphorus removal process is the interaction between different... more Acharacteristic of the biological phosphorus removal process is the interaction between different intracdhrlar components. Therefore, an understanding of the effects of the intracellular components on biologicalphosphorus removal is essential for the practical application of the process. In this study, the stoichiometryof poly-hydroxybutyrate(PHB) to P-uptake and the kinetics of uptake of ortho-phosphatein relation to PHB were investigatedunder aerobic and substrate limitingconditions in batch experiments with activated sludge from a biological phosphorus removal process. The stoichiometryof PHB to P-uptake was investigatedby determination of the degradation rate of PHB under aerobic conditions in the presence and absence of ortho-phosphate in the bulk liquid. The degradation of PHB as a function of time was described by a first-order equation. The presence of ortho-phosphate increased the rate of PHB degradation significantly,confirming that the uptake of ortho-phosphate directly required PHB. The fraction of PHB usedforuptakeof ortho-phosphate from thebulkliquidwasestimatedto be300/.. Furthermore, batchexperiments confirmed that theuptakerate of ortho-phosphate underaerobicconditions washighlydependent on theconcentration of PHBin the biomass.The observeduptakerate of ortho-phosphate as a functionof the PHB concentration was mathematicallydescribed bya Monodequation. Themaximum uptakerateof the sludgewasestimated to be 14(mg-P/g-VSS)/h. The obtainedresultsadd to the understanding of the mechanisms of the biological phosphorus removal processunderthestressconditions withlimitingsubstratesupplies present in thefull-scale wastewater treatmentprocess. Furthermore, theresultsindicatethat controlstrategies to stabilisethe processshouldfocuson a maintenance and optimalutilisationof PHB.@ 1998Ekevier ScienceLtd. All rightsreserved

Water Science and Technology, 1998

This paper is the third of a three-part series summarizing the background to and objectives of th... more This paper is the third of a three-part series summarizing the background to and objectives of the activity of the IAWQ Task Group on River Water Quality Modelling (RWQM). On the basis of the two other papers and a comparison between the best known state of the art river model, QUAL2, and the IAWQ Activated Sludge Model (ASM) No. 1, the Task Group proposes to develop improved conversion models for inclusion in a river water quality model. The model should describe the cycling of oxygen, nitrogen, and phosphorus in both water and sediment, and should be compatible with the ASM to support the development of integrated emission reduction strategies. The model should be particularly well suited to handle problems characterized by significant temporal and spatial influences (e.g. CSOs and NPSs). It should serve for research, education, improved communication, knowledge transfer, regulatory applications such as catchment planning, and improved data collection. Anticipated results of the Task Group effort include (i) standardized conversion sub-models; (ii) a decision support tool to guide model construction and usage; and (iii) case study applications. The model development, which is not intended to result in a software product, is intended to be an open-ended and flexible process to encourage the participation of interested professionals.

Water Science and Technology, 1998

The U.S. EPA QUAL2 model is currently the standard for river water quality modelling. While QUAL2... more The U.S. EPA QUAL2 model is currently the standard for river water quality modelling. While QUAL2 is adequate for the regulatory situation for which it was developed (the U.S. wasteload allocation process), there is a need for a more comprehensive framework for research and teaching. Moreover, QUAL2 and similar models do not address a number of practical problems such as stormwater flow events, nonpoint source pollution, and transient streamflow. Limitations in model formulation affect the ability to close mass balances, to represent sessile bacteria and other benthic processes, and to achieve robust model calibration. Mass balance problems aris e from failure to account for mass in the sediment as well as in the water column and due to the fundamental imprecision of BOD as a state variable.

Microbial community structures were assessed in a two-stage anaerobic digestion system treating f... more Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was ...

The new River Water Quality Model no.1 introduced in the two accompanying papers by and is compre... more The new River Water Quality Model no.1 introduced in the two accompanying papers by and is comprehensive. Shanahan et al. introduced a six-step decision procedure to select the necessary model features for a certain application. This paper specifically addresses one of these steps, i.e. the selection of submodels of the comprehensive biochemical conversion model introduced in Reichert et al. (2000). Specific conditions for inclusion of one or the other conversion process or model component are introduced, as are some general rules that can support the selection. Examples of simplified models are presented.

ABSTRACT Successful river water quality modelling requires the specifi cation of an appropriate m... more ABSTRACT Successful river water quality modelling requires the specifi cation of an appropriate model,structure and process formulation. Both must be related to the compartment,stru cture of running water ecosystems,including their longitudinal, vertical, and lateral zonation patterns. Furtherm ore, the temporal variability of abiotic boundary conditions may be important and must be incorporated by an appropria te choice of model parameters.