This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
Proceedings of the Water Environment Federation, 2013
Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowle... more Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowledge is still insufficient regarding the exact magnitude of the emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Also, the complete N 2 O production mechanisms remain unclear. In order to shed light on N 2 O emissions at real plants, under different weather conditions, continuous field measurements of gaseous nitrous oxide (N 2 O), ammonium (NH 4 + ), nitrate (NO 3 -) and dissolved oxygen (DO) were carried out at the aeration zone of a 750,000 PE wastewater treatment plant. These were complemented with high-frequency lab analyses of important variables at different locations in the plant. N 2 O emissions were analysed by relating it with the aeration flow rate, the DO and other nitrogen-containing components, as well as the influence of dry and wet weather conditions. Spatial differences in N 2 O emissions throughout the aerated zone were also investigated. It could be concluded that ammonia-oxidizing bacteria (AOB) can contribute significantly to N 2 O production compared to the heterotrophic pathway for N 2 O production. Moreover, rather than simply correlating N 2 O production by AOB with DO concentration, the investigation revealed the conditions affecting NH 4 + to be oxidized either more to N 2 O or more to NO 3 -. Under regular dry weather conditions, the measured average N 2 O emission factor at the summer package aeration zone is 0.96% of influent nitrogen load. The N 2 O production by AOB is stimulated by high NH 4 + concentrations, but it is likely that under high DO conditions the fraction of NH 4 + converted to N 2 O is smaller than under low DO conditions while the NO 3 production kept increasing. Under rain events, lower N 2 O emissions were observed.
Proceedings of the Water Environment Federation, 2012
ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the indu... more ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the industry and account for the uncertainty and variability inherent in the wastewater treatment process. Models on the other hand, as implemented in most commercial simulators, do not explicitly account for uncertainty. This paper discusses how to deal with variability and uncertainty in an explicit way when using a dynamic model combined with uncertainty analysis to perform a post-project evaluation. Through the use of time series, the response of the design to the variability of key inputs can be captured in the dynamic model. In order to incorporate uncertainty, selected model parameters can be described with probability density functions (PDF). Scenario analysis can be used to simulate discreet operational conditions or events. Uncertainty can then be propagated to the dynamic model outputs with the use of Monte Carlo simulations. To test this approach, the upgrade of the Eindhoven WWTP (Waterboard De Dommel, The Netherlands) was selected as a case study. The project focused on how variability and uncertainty are incorporated in design guidelines and highlighted key issues linked to the inclusion of the sources of uncertainty in the calibrated model.
This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis o... more This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis of post-upgrade performance data. The case study is that of the Eindhoven wastewater treatment plant upgrade completed in 2006. As a first step, the design process based on a static model was thoroughly analyzed and the choices regarding variability and uncertainty (i.e. safety factors) were made explicit. This involved the interpretation of the design guidelines and other assumptions made by the engineers. As a second step, a (calibrated) dynamic model of the plant was set up, able to reproduce the anticipated variability (duration and frequency). The third step was to define probability density functions for the parameters assumed to be uncertain, and propagate that uncertainty with the dynamic model by means of Monte Carlo simulations. The last step was the statistical evaluation and interpretation of the simulation results. This work should be regarded as a 'learning exercise' increasing the understanding of how and to what extent variability and uncertainty are currently incorporated in design guidelines used in practice and how model-based post-project appraisals could be performed.
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
Proceedings of the Water Environment Federation, 2013
ABSTRACT In the European Union, the Water Framework Directive (WFD) enforces a good ecological an... more ABSTRACT In the European Union, the Water Framework Directive (WFD) enforces a good ecological and chemical status of all surface waters, which is to be accomplished before 2015. Mathematical process models have proven to be a valuable tool in this optimization exercise. A model-based scenario analysis was undertaken to evaluate measures that could be taken to reduce the yearly total nitrogen discharge by the wastewater treatment plant of Eindhoven. Based on the modelling results all stakeholders held an in-depth discussion. In this paper we report about the simulation results obtained during the scenario analysis, which was performed as pre-screening for the global optimization (i.e. taking into account the sewer system, the wastewater treatment plant and the river system), and how these are used in the decision process. The project revealed that increasing the MLSS concentrations in the biological tanks has a beneficial effect on both nitrate (up to 34% improvement) and ammonium removal (up to 25% improvement). Also the relocation of recycle B proved to be a promising option (reducing effluent NO3 concentrations up to 23%). From these results it was concluded by the waterboard that in future scenarios the new location of recycle B was to be maintained as part of any new proposed measure. The interaction with the different stakeholders proved to be really valuable for all and increased the acceptance of the modelling results. This satisfying approach will also be used in future model-based optimization studies at the WWTP of Eindhoven.
Proceedings of the Water Environment Federation, 2012
ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the indu... more ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the industry and account for the uncertainty and variability inherent in the wastewater treatment process. Models on the other hand, as implemented in most commercial simulators, do not explicitly account for uncertainty. This paper discusses how to deal with variability and uncertainty in an explicit way when using a dynamic model combined with uncertainty analysis to perform a post-project evaluation. Through the use of time series, the response of the design to the variability of key inputs can be captured in the dynamic model. In order to incorporate uncertainty, selected model parameters can be described with probability density functions (PDF). Scenario analysis can be used to simulate discreet operational conditions or events. Uncertainty can then be propagated to the dynamic model outputs with the use of Monte Carlo simulations. To test this approach, the upgrade of the Eindhoven WWTP (Waterboard De Dommel, The Netherlands) was selected as a case study. The project focused on how variability and uncertainty are incorporated in design guidelines and highlighted key issues linked to the inclusion of the sources of uncertainty in the calibrated model.
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis o... more This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis of post-upgrade performance data. The case study is that of the Eindhoven wastewater treatment plant upgrade completed in 2006. As a first step, the design process based on a static model was thoroughly analyzed and the choices regarding variability and uncertainty (i.e. safety factors) were made explicit. This involved the interpretation of the design guidelines and other assumptions made by the engineers. As a second step, a (calibrated) dynamic model of the plant was set up, able to reproduce the anticipated variability (duration and frequency). The third step was to define probability density functions for the parameters assumed to be uncertain, and propagate that uncertainty with the dynamic model by means of Monte Carlo simulations. The last step was the statistical evaluation and interpretation of the simulation results. This work should be regarded as a 'learning exercise' increasing the understanding of how and to what extent variability and uncertainty are currently incorporated in design guidelines used in practice and how model-based post-project appraisals could be performed.
Proceedings of the Water Environment Federation, 2013
Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowle... more Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowledge is still insufficient regarding the exact magnitude of the emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Also, the complete N 2 O production mechanisms remain unclear. In order to shed light on N 2 O emissions at real plants, under different weather conditions, continuous field measurements of gaseous nitrous oxide (N 2 O), ammonium (NH 4 + ), nitrate (NO 3 -) and dissolved oxygen (DO) were carried out at the aeration zone of a 750,000 PE wastewater treatment plant. These were complemented with high-frequency lab analyses of important variables at different locations in the plant. N 2 O emissions were analysed by relating it with the aeration flow rate, the DO and other nitrogen-containing components, as well as the influence of dry and wet weather conditions. Spatial differences in N 2 O emissions throughout the aerated zone were also investigated. It could be concluded that ammonia-oxidizing bacteria (AOB) can contribute significantly to N 2 O production compared to the heterotrophic pathway for N 2 O production. Moreover, rather than simply correlating N 2 O production by AOB with DO concentration, the investigation revealed the conditions affecting NH 4 + to be oxidized either more to N 2 O or more to NO 3 -. Under regular dry weather conditions, the measured average N 2 O emission factor at the summer package aeration zone is 0.96% of influent nitrogen load. The N 2 O production by AOB is stimulated by high NH 4 + concentrations, but it is likely that under high DO conditions the fraction of NH 4 + converted to N 2 O is smaller than under low DO conditions while the NO 3 production kept increasing. Under rain events, lower N 2 O emissions were observed.
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
Proceedings of the Water Environment Federation, 2013
Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowle... more Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowledge is still insufficient regarding the exact magnitude of the emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Also, the complete N 2 O production mechanisms remain unclear. In order to shed light on N 2 O emissions at real plants, under different weather conditions, continuous field measurements of gaseous nitrous oxide (N 2 O), ammonium (NH 4 + ), nitrate (NO 3 -) and dissolved oxygen (DO) were carried out at the aeration zone of a 750,000 PE wastewater treatment plant. These were complemented with high-frequency lab analyses of important variables at different locations in the plant. N 2 O emissions were analysed by relating it with the aeration flow rate, the DO and other nitrogen-containing components, as well as the influence of dry and wet weather conditions. Spatial differences in N 2 O emissions throughout the aerated zone were also investigated. It could be concluded that ammonia-oxidizing bacteria (AOB) can contribute significantly to N 2 O production compared to the heterotrophic pathway for N 2 O production. Moreover, rather than simply correlating N 2 O production by AOB with DO concentration, the investigation revealed the conditions affecting NH 4 + to be oxidized either more to N 2 O or more to NO 3 -. Under regular dry weather conditions, the measured average N 2 O emission factor at the summer package aeration zone is 0.96% of influent nitrogen load. The N 2 O production by AOB is stimulated by high NH 4 + concentrations, but it is likely that under high DO conditions the fraction of NH 4 + converted to N 2 O is smaller than under low DO conditions while the NO 3 production kept increasing. Under rain events, lower N 2 O emissions were observed.
Proceedings of the Water Environment Federation, 2012
ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the indu... more ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the industry and account for the uncertainty and variability inherent in the wastewater treatment process. Models on the other hand, as implemented in most commercial simulators, do not explicitly account for uncertainty. This paper discusses how to deal with variability and uncertainty in an explicit way when using a dynamic model combined with uncertainty analysis to perform a post-project evaluation. Through the use of time series, the response of the design to the variability of key inputs can be captured in the dynamic model. In order to incorporate uncertainty, selected model parameters can be described with probability density functions (PDF). Scenario analysis can be used to simulate discreet operational conditions or events. Uncertainty can then be propagated to the dynamic model outputs with the use of Monte Carlo simulations. To test this approach, the upgrade of the Eindhoven WWTP (Waterboard De Dommel, The Netherlands) was selected as a case study. The project focused on how variability and uncertainty are incorporated in design guidelines and highlighted key issues linked to the inclusion of the sources of uncertainty in the calibrated model.
This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis o... more This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis of post-upgrade performance data. The case study is that of the Eindhoven wastewater treatment plant upgrade completed in 2006. As a first step, the design process based on a static model was thoroughly analyzed and the choices regarding variability and uncertainty (i.e. safety factors) were made explicit. This involved the interpretation of the design guidelines and other assumptions made by the engineers. As a second step, a (calibrated) dynamic model of the plant was set up, able to reproduce the anticipated variability (duration and frequency). The third step was to define probability density functions for the parameters assumed to be uncertain, and propagate that uncertainty with the dynamic model by means of Monte Carlo simulations. The last step was the statistical evaluation and interpretation of the simulation results. This work should be regarded as a 'learning exercise' increasing the understanding of how and to what extent variability and uncertainty are currently incorporated in design guidelines used in practice and how model-based post-project appraisals could be performed.
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
Proceedings of the Water Environment Federation, 2013
ABSTRACT In the European Union, the Water Framework Directive (WFD) enforces a good ecological an... more ABSTRACT In the European Union, the Water Framework Directive (WFD) enforces a good ecological and chemical status of all surface waters, which is to be accomplished before 2015. Mathematical process models have proven to be a valuable tool in this optimization exercise. A model-based scenario analysis was undertaken to evaluate measures that could be taken to reduce the yearly total nitrogen discharge by the wastewater treatment plant of Eindhoven. Based on the modelling results all stakeholders held an in-depth discussion. In this paper we report about the simulation results obtained during the scenario analysis, which was performed as pre-screening for the global optimization (i.e. taking into account the sewer system, the wastewater treatment plant and the river system), and how these are used in the decision process. The project revealed that increasing the MLSS concentrations in the biological tanks has a beneficial effect on both nitrate (up to 34% improvement) and ammonium removal (up to 25% improvement). Also the relocation of recycle B proved to be a promising option (reducing effluent NO3 concentrations up to 23%). From these results it was concluded by the waterboard that in future scenarios the new location of recycle B was to be maintained as part of any new proposed measure. The interaction with the different stakeholders proved to be really valuable for all and increased the acceptance of the modelling results. This satisfying approach will also be used in future model-based optimization studies at the WWTP of Eindhoven.
Proceedings of the Water Environment Federation, 2012
ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the indu... more ABSTRACT Design guideline safety factors (SF) are based on the accumulated experience of the industry and account for the uncertainty and variability inherent in the wastewater treatment process. Models on the other hand, as implemented in most commercial simulators, do not explicitly account for uncertainty. This paper discusses how to deal with variability and uncertainty in an explicit way when using a dynamic model combined with uncertainty analysis to perform a post-project evaluation. Through the use of time series, the response of the design to the variability of key inputs can be captured in the dynamic model. In order to incorporate uncertainty, selected model parameters can be described with probability density functions (PDF). Scenario analysis can be used to simulate discreet operational conditions or events. Uncertainty can then be propagated to the dynamic model outputs with the use of Monte Carlo simulations. To test this approach, the upgrade of the Eindhoven WWTP (Waterboard De Dommel, The Netherlands) was selected as a case study. The project focused on how variability and uncertainty are incorporated in design guidelines and highlighted key issues linked to the inclusion of the sources of uncertainty in the calibrated model.
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directiv... more This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems.
This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis o... more This paper illustrates how a dynamic model can be used to evaluate a plant upgrade on the basis of post-upgrade performance data. The case study is that of the Eindhoven wastewater treatment plant upgrade completed in 2006. As a first step, the design process based on a static model was thoroughly analyzed and the choices regarding variability and uncertainty (i.e. safety factors) were made explicit. This involved the interpretation of the design guidelines and other assumptions made by the engineers. As a second step, a (calibrated) dynamic model of the plant was set up, able to reproduce the anticipated variability (duration and frequency). The third step was to define probability density functions for the parameters assumed to be uncertain, and propagate that uncertainty with the dynamic model by means of Monte Carlo simulations. The last step was the statistical evaluation and interpretation of the simulation results. This work should be regarded as a 'learning exercise' increasing the understanding of how and to what extent variability and uncertainty are currently incorporated in design guidelines used in practice and how model-based post-project appraisals could be performed.
Proceedings of the Water Environment Federation, 2013
Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowle... more Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowledge is still insufficient regarding the exact magnitude of the emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Also, the complete N 2 O production mechanisms remain unclear. In order to shed light on N 2 O emissions at real plants, under different weather conditions, continuous field measurements of gaseous nitrous oxide (N 2 O), ammonium (NH 4 + ), nitrate (NO 3 -) and dissolved oxygen (DO) were carried out at the aeration zone of a 750,000 PE wastewater treatment plant. These were complemented with high-frequency lab analyses of important variables at different locations in the plant. N 2 O emissions were analysed by relating it with the aeration flow rate, the DO and other nitrogen-containing components, as well as the influence of dry and wet weather conditions. Spatial differences in N 2 O emissions throughout the aerated zone were also investigated. It could be concluded that ammonia-oxidizing bacteria (AOB) can contribute significantly to N 2 O production compared to the heterotrophic pathway for N 2 O production. Moreover, rather than simply correlating N 2 O production by AOB with DO concentration, the investigation revealed the conditions affecting NH 4 + to be oxidized either more to N 2 O or more to NO 3 -. Under regular dry weather conditions, the measured average N 2 O emission factor at the summer package aeration zone is 0.96% of influent nitrogen load. The N 2 O production by AOB is stimulated by high NH 4 + concentrations, but it is likely that under high DO conditions the fraction of NH 4 + converted to N 2 O is smaller than under low DO conditions while the NO 3 production kept increasing. Under rain events, lower N 2 O emissions were observed.
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Papers by Tony Flameling