The CAPWAT project is a Dutch joint industry project (JIP) on capacity losses in pressurized wast... more The CAPWAT project is a Dutch joint industry project (JIP) on capacity losses in pressurized wastewater mains. The project has been primarily funded by the Dutch water boards, consultants and a pump manufacturer. Since its start in 2003, the JIP CAPWAT included a scientific track and a track on practical implications. This set-up has guaranteed a continuous two-way interaction between practice and research. Feedback from practice has focused and adjusted the research questions during the project and the project set-up has enabled an immediate transfer of scientific results towards practical guidelines. This paper addresses a number of issues, both managerial and technical: 1 It sketches the context from which the CAPWAT project was initiated. 2 It details the research track and practical track. 3 Furthermore, the paper addresses the key findings of the CAPWAT project, as well as its implications for the water industry.
The proven benefits of pressure management in distribution systems now include not only leakage c... more The proven benefits of pressure management in distribution systems now include not only leakage control, but also water conservation, burst reduction and Asset Management and customer service benefits. The paper will provide an overview of latest improvements in several aspects of analysis, prediction and validation of pressure management benefits. Six years ago, the publication by IWA Water Loss Task Force members of data showing significant reductions in mains and services bursts, from 112 Pressure Management Zones (PMZs) in 12 countries, helped to promote international interest in control of burst frequencies by pressure management. A conceptual explanation (‘the straw that breaks the camel’s back), coupled with calculation of simple separate Burst Frequency Indices (BFIs) for mains and services, has proved capable of rapidly identifying distribution zones where significant reductions in bursts could be expected, on mains and/or service connections, if pressure transients and/or excess operating pressures can be reduced. Further more recent developments include an improved prediction equation for reduction in numbers and frequencies of bursts for individual Zones, the impact of pressure management on seasonal changes in burst frequencies, and initial quantification of the financial benefits of extension of asset life. Training and coaching, including the use of specialist leakage software to facilitate and support the learning process and knowledge transfer in water utilities, are the way forward to help utilities to achieve substantial improvements in the field of water loss management. The paper summarises the recent international progress in analysis, prediction and implementation of pressure management and transient analysis to reduce bursts and extend infrastructure life and highlights the advantages of structured training and knowledge transfer on these topics.
Today's ultrafiltration processes use permeate flow reversal to remove fouling deposits o... more Today's ultrafiltration processes use permeate flow reversal to remove fouling deposits on the feed side of ultrafiltration membranes. We report an as effective method: the opening and rapid closing of a valve on the permeate side of an ultrafiltration module. The sudden valve closure generates pressure fluctuations due to fluid inertia and is commonly known as "water hammer". Surface water was filtrated in hollow fiber ultrafiltration membranes with a small (5%) crossflow. Filtration experiments above sustainable flux levels (>125 l (m2h)(-1)) show that a periodic closure of a valve on the permeate side improves filtration performance as a consequence of reduced fouling. It was shown that this effect depends on flux and actuation frequency of the valve. The time period that the valve was closed proved to have no effect on filtration performance. The pressure fluctuations generated by the sudden stop in fluid motion due to the valve closure are responsible for the effect of fouling reduction. High frequency recording of the dynamic pressure evolution shows water hammer related pressure fluctuations to occur in the order of 0.1 bar. The pressure fluctuations were higher at higher fluxes (higher velocities) which is in agreement with the theory. They were also more effective at higher fluxes with respect to fouling mitigation.
It remains unknown how lateral house connections affect the performance of the sewer system, sinc... more It remains unknown how lateral house connections affect the performance of the sewer system, since the assessment of serviceability is mainly based on the state of the main sewer system. Further insight into the contribution of lateral house connections to the overall level of service provided can aid to target investments to parts of the system where it is most effective. To this end, techniques from the reliability theory were applied to a commercial sewer maintenance database to quantify the impact of lateral house connections on the serviceability of sewer systems. Analysis of the data showed that the failures follow a Poisson distribution. A comparison of the derived failure rate with values obtained from a different study revealed that the blockage rate of lateral house connections is an order of magnitude greater than the failure rate of the dominant mechanism of main sewer systems, thereby making the impact of lateral house connections on the serviceability of sewer systems ...
Critical Infrastructures are an essential asset in modern societies and our everyday life is heav... more Critical Infrastructures are an essential asset in modern societies and our everyday life is heavily dependent on their reliable and secure operation. The problem of controlling and managing critical infrastructures is becoming more and more difficult as they are increasing in size due to the growing demand for the services they provide and the geographical spread required. As these infrastructures become larger and more complex, fewer people understand how these networks work and the interactions between all the components. Thus, models are necessary so as to accurately predict their behavior under steady state or under failure/attack scenarios. This chapter provides a review on modeling and simulation approaches of critical infrastructures and in particular of electric power, telecommunications, water supply and drainage systems, and transportation systems.
ABSTRACT Despite all recent developments to improve the hydraulic performance of components in ul... more ABSTRACT Despite all recent developments to improve the hydraulic performance of components in ultrafiltration and reverse osmosis plants, from advanced membrane modules to complex energy recovery devices, only little attention is being paid to enhance the plant operation as a fully integrated system. In practice, different hydraulic devices are chosen based on their individual performances without considering associated hydraulic interactions among the devices. This becomes a matter of concern, especially during transient events when a change in the operation of one device may lead to unacceptable pressure and flow rate fluctuations through the plant and eventually costly damages. Although several excellent books have been written on fluid transients for pipeline systems, there is still a need for a guideline on the hydraulic analysis of ultrafiltration and reverse osmosis plants which include complex and vulnerable hydraulic components such as UF and RO membranes, energy recovery devices, and solenoid valves. This study provides a guideline for the integrated hydraulic design of plants with a focus on modeling of UF and RO units, which leads to a more robust, reliable, and water-tight system.
Energieverlies leidingen beperkt door terugkoppeling praktijk naar ontwerp en beheer.Water Manage... more Energieverlies leidingen beperkt door terugkoppeling praktijk naar ontwerp en beheer.Water ManagementCivil Engineering and Geoscience
Wordt stedelijk waterbeheer steeds duurzamer? De kennis over stedelijk waterbeheer heeft de afgel... more Wordt stedelijk waterbeheer steeds duurzamer? De kennis over stedelijk waterbeheer heeft de afgelopen decennia een grote vlucht genomen. Maar dat dit nog geen garantie voor duurzaam stedelijk waterbeheer biedt, was goed terug te zien op het congres over dit onderwerp in Porto Alegre (Brazilië). Inzicht hebben in de effecten van klimaatverandering is nog maar een eerste stap naar steden die voldoende beschermd zijn voor overstromingen en gezond water bieden aan hun inwoners. Ervaringsuitwisseling van stedelijk waterdeskundigen van over de hele wereld helpt daar in ieder geval bij.
The Shuweihat Water Transmission Scheme (SWTS, UAE) consists of a twin DN1600 DI PN25 pipeline tr... more The Shuweihat Water Transmission Scheme (SWTS, UAE) consists of a twin DN1600 DI PN25 pipeline transmitting 150 MIGD over 250 km from Shuweihat Desalination plant to Mussafah (Abu Dhabi city). The Scheme is divided in two subsequent systems, each with a tank farm and a pump station delivering water to downstream terminal reservoirs and direct consumers. The first system (Lot A) transmits water from Shuweihat to Mirfa (100 km). The second (Lot C) is from Mirfa to Mussafah (150 km). The pipeline follows roughly the UAE coastline and the profile is generally flat with a few local high points. The surge study of the Lot C system investigated a large number of scenarios and resulted in the design of surge protection equipments and control systems. The surge protection equipment consists of 16 x 121 m3 (1936 m3) innovative vertical non-vented air vessels, invented by Deltares. The innovation includes a passive air release valve at a strategic elevation on the air vessel. This air release valve opens if the water level drops below the float level. At this water level the air pressure is super-atmospheric so that air is released from the air vessel to prevent draining. This innovation was driven by the initial findings of the surge analysis where it became apparent that 22 x 220 m3 (4840 m3) air vessels would have been required. These large vessels were the result of a double constraint. On the one hand, the initial air mass had to be sufficient to allow a proper expansion of the vessels and thus the protection of the pipeline against excessive negative pressures. On the other hand, a very small initial air mass was required due to the lack of backpressure. This meant that the air pocket was expanding by a factor exceeding 20, resulting in the emptying of the vessels. In this paper, we will describe the hydraulic model of the hybrid air vessel, detail the benefits of the new design and discuss the cost savings compared to conventional air vessels. It is concluded that the hybrid air vessel has saved over 50% of the required air vessels total volume. Considering the size of air vessels initially required, the costs savings in terms of surge protection of the SWTS Lot C system were cut in excess of 60%.
This paper presents a validation of the surge modeling results as well as lessons learnt from the... more This paper presents a validation of the surge modeling results as well as lessons learnt from the commissioning test of the Shuweihat Water Transmission Scheme in the UAE. The Scheme is divided in two systems, The first system (Lot A) transmits water from Shuweihat to Mirfa (100 km). The second (Lot C) is from Mirfa to Mussafah (150 km). The focus of this paper is on the model predictions and field data recorded by the SCADA system during full pump trip and valve closure events. The validation was performed during the commissioning test and showed a perfect match between the prediction and measurement of pressure and flow of the first wave. This paper also intends to highlight lessons learnt during the commissioning test and in particular the major risk that is caused by inaccurate manufacturer data. On the first day of the commissioning test, a near incident took place where the pressure during valve closure unexpectedly exceeded the pressure rating by 16%. Damage to the pipeline was avoided by pressing the emergency trip pushbutton of the pumps thereby preventing the pipeline from being exposed to the full pressure rise. The post-incident investigation revealed that the control valve characteristics provided and certified by the manufacturer were inaccurate. A difference in Kv of up to 20% was measured for valve positions below 40% open and the valves were fully closed at 5% opening. The control valve characteristics were recalibrated on site and the valve closure pattern was adapted. The commissioning test was resumed and completed flawlessly.
In the mixing process of water with different salinities a large amount of energy is released, wh... more In the mixing process of water with different salinities a large amount of energy is released, which is normally converted into heat if fresh water rivers enter estuaries and seas. This energy, often referred to as Blue Energy, may be extracted by two different processes: Reversed Electrodialysis (RED) or Pressure Retarded Osmosis (PRO). The Netherlands has a number of locations where large fresh water flows enter saline water bodies via man-made structures, creating opportunities for Blue Energy applications. This paper investigates the hydrodynamic and mass transfer processes at two different scales, the estuarine scale and the membrane module scale, for a specific site in The Netherlands: IJmuiden. The physics at these two very different scales both play a role in the performance of a potential Blue Energy power plant. On the estuarine scale-the tidal and density driven hydrodynamic scale-the performance of a Blue Energy power plant depends primarily on the available salinity gradient. In many locations, natural mixing of saline and fresh water reduces the maximum exploitable salinity gradient. Therefore, an adequate intake and outfall layout is required to optimize the performance of a Blue Energy plant. Particulate matter content is another issue to be addressed: at present, the required pre-filtration would account for the largest energy losses in the Blue Energy process. A model at the module scale shows that delicate balances exist between most of the design parameters of a Blue Energy power plant and that for salinity gradients present in IJmuiden a net energy production in the order of 5 to 7 MW can be expected.
The CAPWAT project is a Dutch joint industry project (JIP) on capacity losses in pressurized wast... more The CAPWAT project is a Dutch joint industry project (JIP) on capacity losses in pressurized wastewater mains. The project has been primarily funded by the Dutch water boards, consultants and a pump manufacturer. Since its start in 2003, the JIP CAPWAT included a scientific track and a track on practical implications. This set-up has guaranteed a continuous two-way interaction between practice and research. Feedback from practice has focused and adjusted the research questions during the project and the project set-up has enabled an immediate transfer of scientific results towards practical guidelines. This paper addresses a number of issues, both managerial and technical: 1 It sketches the context from which the CAPWAT project was initiated. 2 It details the research track and practical track. 3 Furthermore, the paper addresses the key findings of the CAPWAT project, as well as its implications for the water industry.
The proven benefits of pressure management in distribution systems now include not only leakage c... more The proven benefits of pressure management in distribution systems now include not only leakage control, but also water conservation, burst reduction and Asset Management and customer service benefits. The paper will provide an overview of latest improvements in several aspects of analysis, prediction and validation of pressure management benefits. Six years ago, the publication by IWA Water Loss Task Force members of data showing significant reductions in mains and services bursts, from 112 Pressure Management Zones (PMZs) in 12 countries, helped to promote international interest in control of burst frequencies by pressure management. A conceptual explanation (‘the straw that breaks the camel’s back), coupled with calculation of simple separate Burst Frequency Indices (BFIs) for mains and services, has proved capable of rapidly identifying distribution zones where significant reductions in bursts could be expected, on mains and/or service connections, if pressure transients and/or excess operating pressures can be reduced. Further more recent developments include an improved prediction equation for reduction in numbers and frequencies of bursts for individual Zones, the impact of pressure management on seasonal changes in burst frequencies, and initial quantification of the financial benefits of extension of asset life. Training and coaching, including the use of specialist leakage software to facilitate and support the learning process and knowledge transfer in water utilities, are the way forward to help utilities to achieve substantial improvements in the field of water loss management. The paper summarises the recent international progress in analysis, prediction and implementation of pressure management and transient analysis to reduce bursts and extend infrastructure life and highlights the advantages of structured training and knowledge transfer on these topics.
Today's ultrafiltration processes use permeate flow reversal to remove fouling deposits o... more Today's ultrafiltration processes use permeate flow reversal to remove fouling deposits on the feed side of ultrafiltration membranes. We report an as effective method: the opening and rapid closing of a valve on the permeate side of an ultrafiltration module. The sudden valve closure generates pressure fluctuations due to fluid inertia and is commonly known as "water hammer". Surface water was filtrated in hollow fiber ultrafiltration membranes with a small (5%) crossflow. Filtration experiments above sustainable flux levels (>125 l (m2h)(-1)) show that a periodic closure of a valve on the permeate side improves filtration performance as a consequence of reduced fouling. It was shown that this effect depends on flux and actuation frequency of the valve. The time period that the valve was closed proved to have no effect on filtration performance. The pressure fluctuations generated by the sudden stop in fluid motion due to the valve closure are responsible for the effect of fouling reduction. High frequency recording of the dynamic pressure evolution shows water hammer related pressure fluctuations to occur in the order of 0.1 bar. The pressure fluctuations were higher at higher fluxes (higher velocities) which is in agreement with the theory. They were also more effective at higher fluxes with respect to fouling mitigation.
It remains unknown how lateral house connections affect the performance of the sewer system, sinc... more It remains unknown how lateral house connections affect the performance of the sewer system, since the assessment of serviceability is mainly based on the state of the main sewer system. Further insight into the contribution of lateral house connections to the overall level of service provided can aid to target investments to parts of the system where it is most effective. To this end, techniques from the reliability theory were applied to a commercial sewer maintenance database to quantify the impact of lateral house connections on the serviceability of sewer systems. Analysis of the data showed that the failures follow a Poisson distribution. A comparison of the derived failure rate with values obtained from a different study revealed that the blockage rate of lateral house connections is an order of magnitude greater than the failure rate of the dominant mechanism of main sewer systems, thereby making the impact of lateral house connections on the serviceability of sewer systems ...
Critical Infrastructures are an essential asset in modern societies and our everyday life is heav... more Critical Infrastructures are an essential asset in modern societies and our everyday life is heavily dependent on their reliable and secure operation. The problem of controlling and managing critical infrastructures is becoming more and more difficult as they are increasing in size due to the growing demand for the services they provide and the geographical spread required. As these infrastructures become larger and more complex, fewer people understand how these networks work and the interactions between all the components. Thus, models are necessary so as to accurately predict their behavior under steady state or under failure/attack scenarios. This chapter provides a review on modeling and simulation approaches of critical infrastructures and in particular of electric power, telecommunications, water supply and drainage systems, and transportation systems.
ABSTRACT Despite all recent developments to improve the hydraulic performance of components in ul... more ABSTRACT Despite all recent developments to improve the hydraulic performance of components in ultrafiltration and reverse osmosis plants, from advanced membrane modules to complex energy recovery devices, only little attention is being paid to enhance the plant operation as a fully integrated system. In practice, different hydraulic devices are chosen based on their individual performances without considering associated hydraulic interactions among the devices. This becomes a matter of concern, especially during transient events when a change in the operation of one device may lead to unacceptable pressure and flow rate fluctuations through the plant and eventually costly damages. Although several excellent books have been written on fluid transients for pipeline systems, there is still a need for a guideline on the hydraulic analysis of ultrafiltration and reverse osmosis plants which include complex and vulnerable hydraulic components such as UF and RO membranes, energy recovery devices, and solenoid valves. This study provides a guideline for the integrated hydraulic design of plants with a focus on modeling of UF and RO units, which leads to a more robust, reliable, and water-tight system.
Energieverlies leidingen beperkt door terugkoppeling praktijk naar ontwerp en beheer.Water Manage... more Energieverlies leidingen beperkt door terugkoppeling praktijk naar ontwerp en beheer.Water ManagementCivil Engineering and Geoscience
Wordt stedelijk waterbeheer steeds duurzamer? De kennis over stedelijk waterbeheer heeft de afgel... more Wordt stedelijk waterbeheer steeds duurzamer? De kennis over stedelijk waterbeheer heeft de afgelopen decennia een grote vlucht genomen. Maar dat dit nog geen garantie voor duurzaam stedelijk waterbeheer biedt, was goed terug te zien op het congres over dit onderwerp in Porto Alegre (Brazilië). Inzicht hebben in de effecten van klimaatverandering is nog maar een eerste stap naar steden die voldoende beschermd zijn voor overstromingen en gezond water bieden aan hun inwoners. Ervaringsuitwisseling van stedelijk waterdeskundigen van over de hele wereld helpt daar in ieder geval bij.
The Shuweihat Water Transmission Scheme (SWTS, UAE) consists of a twin DN1600 DI PN25 pipeline tr... more The Shuweihat Water Transmission Scheme (SWTS, UAE) consists of a twin DN1600 DI PN25 pipeline transmitting 150 MIGD over 250 km from Shuweihat Desalination plant to Mussafah (Abu Dhabi city). The Scheme is divided in two subsequent systems, each with a tank farm and a pump station delivering water to downstream terminal reservoirs and direct consumers. The first system (Lot A) transmits water from Shuweihat to Mirfa (100 km). The second (Lot C) is from Mirfa to Mussafah (150 km). The pipeline follows roughly the UAE coastline and the profile is generally flat with a few local high points. The surge study of the Lot C system investigated a large number of scenarios and resulted in the design of surge protection equipments and control systems. The surge protection equipment consists of 16 x 121 m3 (1936 m3) innovative vertical non-vented air vessels, invented by Deltares. The innovation includes a passive air release valve at a strategic elevation on the air vessel. This air release valve opens if the water level drops below the float level. At this water level the air pressure is super-atmospheric so that air is released from the air vessel to prevent draining. This innovation was driven by the initial findings of the surge analysis where it became apparent that 22 x 220 m3 (4840 m3) air vessels would have been required. These large vessels were the result of a double constraint. On the one hand, the initial air mass had to be sufficient to allow a proper expansion of the vessels and thus the protection of the pipeline against excessive negative pressures. On the other hand, a very small initial air mass was required due to the lack of backpressure. This meant that the air pocket was expanding by a factor exceeding 20, resulting in the emptying of the vessels. In this paper, we will describe the hydraulic model of the hybrid air vessel, detail the benefits of the new design and discuss the cost savings compared to conventional air vessels. It is concluded that the hybrid air vessel has saved over 50% of the required air vessels total volume. Considering the size of air vessels initially required, the costs savings in terms of surge protection of the SWTS Lot C system were cut in excess of 60%.
This paper presents a validation of the surge modeling results as well as lessons learnt from the... more This paper presents a validation of the surge modeling results as well as lessons learnt from the commissioning test of the Shuweihat Water Transmission Scheme in the UAE. The Scheme is divided in two systems, The first system (Lot A) transmits water from Shuweihat to Mirfa (100 km). The second (Lot C) is from Mirfa to Mussafah (150 km). The focus of this paper is on the model predictions and field data recorded by the SCADA system during full pump trip and valve closure events. The validation was performed during the commissioning test and showed a perfect match between the prediction and measurement of pressure and flow of the first wave. This paper also intends to highlight lessons learnt during the commissioning test and in particular the major risk that is caused by inaccurate manufacturer data. On the first day of the commissioning test, a near incident took place where the pressure during valve closure unexpectedly exceeded the pressure rating by 16%. Damage to the pipeline was avoided by pressing the emergency trip pushbutton of the pumps thereby preventing the pipeline from being exposed to the full pressure rise. The post-incident investigation revealed that the control valve characteristics provided and certified by the manufacturer were inaccurate. A difference in Kv of up to 20% was measured for valve positions below 40% open and the valves were fully closed at 5% opening. The control valve characteristics were recalibrated on site and the valve closure pattern was adapted. The commissioning test was resumed and completed flawlessly.
In the mixing process of water with different salinities a large amount of energy is released, wh... more In the mixing process of water with different salinities a large amount of energy is released, which is normally converted into heat if fresh water rivers enter estuaries and seas. This energy, often referred to as Blue Energy, may be extracted by two different processes: Reversed Electrodialysis (RED) or Pressure Retarded Osmosis (PRO). The Netherlands has a number of locations where large fresh water flows enter saline water bodies via man-made structures, creating opportunities for Blue Energy applications. This paper investigates the hydrodynamic and mass transfer processes at two different scales, the estuarine scale and the membrane module scale, for a specific site in The Netherlands: IJmuiden. The physics at these two very different scales both play a role in the performance of a potential Blue Energy power plant. On the estuarine scale-the tidal and density driven hydrodynamic scale-the performance of a Blue Energy power plant depends primarily on the available salinity gradient. In many locations, natural mixing of saline and fresh water reduces the maximum exploitable salinity gradient. Therefore, an adequate intake and outfall layout is required to optimize the performance of a Blue Energy plant. Particulate matter content is another issue to be addressed: at present, the required pre-filtration would account for the largest energy losses in the Blue Energy process. A model at the module scale shows that delicate balances exist between most of the design parameters of a Blue Energy power plant and that for salinity gradients present in IJmuiden a net energy production in the order of 5 to 7 MW can be expected.
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Papers by Ivo Pothof