Search

Large water distribution systems (WDSs) are networks with both topological and behavioural complexity. Thereby, it is usually difficult to identify the key features of the properties of the system, and subsequently all the critical components within the system for a given purpose of design or control. One way is, however, to more explicitly visualize the network structure and interactions between components by dividing a WDS into a number of clusters (subsystems). Accordingly, this paper introduces a clustering strategy that decomposes WDSs into clusters with stronger internal connections than external connections. The detected cluster layout is very similar to the community structure of the served urban area. As WDSs may expand along with urban development in a community-by-community manner, the correspondingly formed distribution clusters may reveal some crucial configurations of WDSs. For verification, the method is applied to identify all the critical links during firefighting for the vulnerability analysis of a real-world WDS. Moreover, both the most critical pipes and clusters are addressed, given the consequences of pipe failure. Compared with the enumeration method, the method used in this study identifies the same group of the most critical components, and provides similar criticality prioritizations of them in a more computationally efficient time. [ABSTRACT FROM AUTHOR]

This paper summarises the physicochemical and microbiological quality of water from a rainwater harvesting (RWH) system in a UK-based office building. 7 microbiological and 34 physicochemical parameters were analysed during an 8 month period. Physicochemically, harvested rainwater quality posed little health risk; most parameters showed concentrations below widely used guideline levels for drinking water. However, RWH system components (e.g. fittings and down pipes) appear to be affected soft water corrosion, resulting in high concentrations of some metals (copper, zinc and aluminium). This suggests the material selection of such fittings should be considered keeping in view the hardness of rainwater of an area. Microbiologically, Cryptosporidium, Salmonella and Legionella were not present in the samples analysed. However, faecal coliform counts were high at the beginning of the study, but did decrease over time in weak correlation with increasing pH. Enterococcus faecalis displayed counts consistently above UK rainwater harvesting standards. Inappropriate roof and rainwater good design, as well as material selection appear to be responsible for the reduced microbial quality, as they promoted contributions from avian sources and inhibited cleaning activities. Building and RWH system designs require greater consideration of local factors, which are critical for optimising harvested rainwater quality, to prevent both the development of contaminated sediments and health impacts. [ABSTRACT FROM AUTHOR]

The rate of uptake of rainwater harvesting (RWH) in the UK has been slow to date, but is expected to gain momentum in the near future. The designs of two different new-build rainwater harvesting systems, based on simple methods, are evaluated using three different design methods, including a continuous simulation modelling approach. The RWH systems are shown to fulfill 36% and 46% of WC demand. Financial analyses reveal that RWH systems within large commercial buildings maybe more financially viable than smaller domestic systems. It is identified that design methods based on simple approaches generate tank sizes substantially larger than the continuous simulation. Comparison of the actual tank sizes and those calculated using continuous simulation established that the tanks installed are oversized for their associated demand level and catchment size. Oversizing tanks can lead to excessive system capital costs, which currently hinders the uptake of systems. Furthermore, it is demonstrated that the catchment area size is often overlooked when designing UK-based RWH systems. With respect to these findings, a recommendation for a transition from the use of simple tools to continuous simulation models is made. [ABSTRACT FROM AUTHOR]

Numerous policy vehicles have been introduced in the UK promoting the use of rainwater harvesting (RWH). However, an 'implementation deficit' exists where legislation limits action by failing to provide adequate support mechanisms. This study uses an interdisciplinary approach to construct a framework to address the issue of overcoming this deficit. Evidence bases have identified six deficit categories, which confirm a lack of enabling of stakeholders. Outline recommendations, such as coordinated information provision and reconsideration of incentive schemes are made in relation to these categories to complete the framework for supporting RWH in the UK. [ABSTRACT FROM AUTHOR]

Simulation models are now available to represent the sewer network, wastewater treatment plant and receiving water as an integrated system. These models can be combined with optimisation methods to improve overall system performance through optimal control. Evolutionary algorithms (EAs) have been proven to be a powerful method in developing optimal control strategies; however, the intensive computational requirement of these methods imposes a limit on their application. This paper explores the potential of surrogate modelling in multiobjective optimisation of urban wastewater systems with a limited number of model simulations. A surrogate based method, ParEGO, is combined with an integrated urban wastewater model to solve real time control problems. This method is compared with the popular NSGA II, by using performance indicators: the hypervolume indicator, additive binary 1-indicator and attainment surface. Comparative results show that ParEGO is an efficient and effective method in deriving optimal control strategies for multiple objective control problems with a small number of simulations. It is suggested that ParEGO can greatly improve computational efficiency in the multiobjective optimisation process, particularly for complex urban wastewater systems. [ABSTRACT FROM AUTHOR]

Typically, performance evaluation of new developed methodologies is based on one or more case studies. The investigation of multiple real world case studies is tedious and time consuming. Moreover extrapolating conclusions from individual investigations to a general basis is arguable and sometimes even wrong. In this article a stochastic approach is presented to evaluate new developed methodologies on a broader basis. For the approach the Matlab-tool "Case Study Generator" is developed which generates a variety of different virtual urban drainage systems automatically using boundary conditions e.g. length of urban drainage system, slope of catchment surface, etc. as input. The layout of the sewer system is based on an adapted Galton-Watson branching process. The sub catchments are allocated considering a digital terrain model. Sewer system components are designed according to standard values. In total, 10,000 different virtual case studies of urban drainage system are generated and simulated. Consequently, simulation results are evaluated using a performance indicator for surface flooding. Comparison between results of the virtual and two real world case studies indicates the promise of the method. The novelty of the approach is that it is possible to get more general conclusions in contrast to traditional evaluations with few case studies. [ABSTRACT FROM AUTHOR]

This paper describes a study of the potential effects of climate change on the design and performance of sewer storage tanks. A long-term synthetic rainfall time-series has been derived based on the IPPC medium-high emission scenario for a case study in London. Results indicate a 35% increase in the number of storm events that cause filling of the tank and a 57% increase in the average volume of storage required. A method to estimate the required future storage volume for any given return period has been developed and described. Indications are that significantly larger storage volumes will be required to maintain the same level of flood protection. [ABSTRACT FROM AUTHOR]

This paper describes a full-scale physical model and its application to investigate the effectiveness/performance of small-bore sewers for a range of operational and design parameters. The implementation methodology involves observing the movement of synthetic gross solids in three small bore sewers (150, 100 and 75 mm diameter) for different volumes of simulated flush waves and gradients. The simulated flush waves were generated, using an automated wave sequencer, for three different flush volumes (3, 4.5 and 6 likes). To investigate the impact of solid shape factor, a number of tests were carried out using synthetic solids in combination with toilet tissue paper. In total, more than 1,000 tests were performed for different operational and design parameter combinations. Results obtained to date have confirmed earlier studies, particularly with respect to the role of flush volume in solids transport, and identified the impact of gradient variation and its significance particularly in small-bore sewers receiving low flush volume. Results from the physical model application exercise will be used to propose new design guidelines for wastewater collection systems with specific consideration to new developments and inform the decision support system, currently being developed as pan of a research project on water cycle management for new developments (WAND). [ABSTRACT FROM AUTHOR]

The paper discusses issues of decision support within the context of sustainable development and more specifically sustainable water cycle management to provide a context and a rationale for the decision support approach adopted within an on-going UK EPSRC-funded project, WaND. The paper proposes a set-up for a flexible, upgradeable, efficient and modular decision support framework and associated tools. Furthermore, the paper presents early prototypes of three decision support tools developed within the proposed framework including initial results for one of them. [ABSTRACT FROM AUTHOR]

An extensive series of experiments has been carried out to investigate the movement mechanisms and behaviour of large solids in small sewers. This paper describes the development, calibration and verification of a model (SOLID) based on data obtained from the experimental rig. It is used to predict solid movement with respect to 'limiting solid transport distance'. Key model parameters are the coefficients of static and dynamic friction, the shape factor of amorphous solids and the flow bypass coefficient. The model is shown to successfully represent the movement of a large solid down a small pipe, where the solid is moving as a sliding, leaking dam, particularly the first 'hop'. Limitations of the model include a limited facility to well represent multiple hops and the need for closely spaced computational nodes leading to small time steps, and long run times. [ABSTRACT FROM AUTHOR]

An experimental and modelling study has been carried out to investigate the movement mechanisms and behaviour of large sanitary solids in small sewers. The overall performance of the model has already been verified in terms of limiting solids transport distance, but in this paper the wave profile across the solid is also shown to fit model predictions well when compared visually. Further insight into how solids behave is also explored in this paper by plotting the interplay of the main horizontal and vertical forces acting on the solid. These results illustrate the dynamics of movement initiation, transport and deposition and indicate the most important forces. Model predictions of movement 'time per hop' have also been experimentally verified, giving further credence to the model. Experimental verification of the magnitude of the forces involved is planned. [ABSTRACT FROM AUTHOR]

Describes the first part of an on-going project which aims at establishing an enhanced procedure for assessing the real-time control potential for the entire urban wastewater system. Integrated modeling; Optimization; Screening procedure.

This paper aims to use quantitative risk analysis, risk modelling and simulation modelling tools to assess the performance of a proprietary single house grey water recycling system. A preliminary Hazard and Operability study (HAZOP) identified the main hazards, both health related and economic, associated with installing the recycling system in a domestic environment. The health related consequences of system failure were associated with the presence of increased concentrations of micro-organisms at the point of use, due to failure of the disinfection system and/or the pump. The risk model was used to assess the increase in the probability of infection for a particular genus of micro-organism, Salmonella spp, during disinfection failure. The increase in the number of cases of infection above a base rate rose from 0.001% during normal operation, to 4% for a recycling system with no disinfection. The simulation model was used to examine the possible effects of pump failure. The model indicated that the anaerobic COD release rate in the system storage tank increases over time and dissolved oxygen decreases during this failure mode. These conditions are likely to result in odour problems. [ABSTRACT FROM AUTHOR]

This paper aims to use quantitative risk analysis, risk modeling andsimulation modeling tools to assess the performance of a proprietarysingle house grey water recycling system. A preliminary Hazard and Operability study (HAZOP) identified the main hazards, both health related and economic, associated with installing the recycling system ina domestic environment. The health related consequences of system failure were associated with the presence of increased concentrations of micro-organisms at the point of use, due to failure of the disinfection system and/or the pump. The risk model was used to assess the increase in the probability of infection for a particular genus of micro-organism, Salmonella spp, during disinfection failure. The increasein the number of cases of infection above a base rate rose from 0.001% during normal operation, to 4% for a recycling system with no disinfection. The simulation model was used to examine the possible effects of pump failure. The model indicated that the anaerobic COD release rate in the system storage tank increases over time and dissolved oxygen decreases during this failure mode. These conditions are likelyto result in odor problems. [ABSTRACT FROM AUTHOR]

Abstract unavailable. [ABSTRACT FROM AUTHOR]

Abstract unavailable. [ABSTRACT FROM AUTHOR]

Abstract unavailable. [ABSTRACT FROM AUTHOR]

For a sustainable urban future, society must move towards the goal of efficient and appropriate water use. Reuse of domestic greywater and rainwater has a significant role to play in this task. In this study, rainfall time series have been used in conjunction with estimates of domestic water appliance usage generated by the Monte-Carlo simulation technique to predict long term system performance. Model resultsshow that changes in the attributes of household occupancy, roof area, appliance type and storage volume affect the water saving efficiency of a single store reuse system. Considering greywater and rainwater in combination, the greatest rate of increase of efficiency with storage size occurs in the range 0-100 litres. Further analysis of small volume storage and reuse indicates that savings of up to 80% of theWC flush water can be made with less than 50 litres storage. However, the collection of rainwater in addition to greywater in a single store reuse system offers little improvement in water saving efficiency. Small volume domestic water reuse systems lend themselves to application in the urban housing environment and therefore offer potential in the move towards a more sustainable city. [ABSTRACT FROM AUTHOR]

When attempting to assess the relative sustainability of a process or practice, it is important to be able to use measures which are appropriate. Sustainability can be viewed at different levels. At one level for any given process, the closing of cycles in terms of resource use and outputs (products and waste) may be an aspiration, and make that process in itself sustainable. However, the process may be intrinsically unsustainable when considered within a broader context accounting for all of the economic, ecological and socio-political implications. Traditionally sustainable indicators have been used as a measure to assess increasing or decreasing sustainability, following detailed analyses to define what the appropriate indicators should be. A current UK project investigating the options for the most sustainable means of disposal of domestic sanitary wastes requires measures to assist in the evaluation of the options. This paper reviews the use of indicators in the context of the current project and municipal water systems, and illustrates how an integrated approach may be envisaged incorporating economics, life cycle analysis and risk assessment as part of a framework to assist decision makers when deciding whether changes to systems or practices are likely to be more or less sustainable. A major conclusion is that any moves to introduce sustainable systems can only be made in conjunction with the system users - the public, who must be involved in the formulation of any new practices whichrequire a change in lifestyle. [ABSTRACT FROM AUTHOR]

Abstract unavailable. [ABSTRACT FROM AUTHOR]

The paper describes the first stages of a study of the origin, transport, and fate of sewer gross solids. The background to the project, its overall plan, and relevant previous studies are outlined. Progress to-date is described. A laboratory study of physical degradation ofgross solids has confirmed general existing field observations that many sanitary solids undergo little degradation, whereas toilet paperand faeces are readily degraded. A study of solid advection and deposition in a laboratory pipe system has covered a wide variety of sanitary and artificial solids. The velocity at which sanitary solids areadvected with the flow has been observed to be similar for most solids in spite of a considerable range of shapes and sizes. Pipe-fill conditions, introducing the retarding effect of the pipe wall at the soffit, have tended to reduce solid velocities especially for floating solids. Generally the advective velocity of artificial solids of the same material and shape has not varied significantly with solid size.However size has had a clearer influence on deposition: with decreasing size, solids of the same density have been deposited at lower values of depth and velocity. [ABSTRACT FROM AUTHOR]

The issue of sustainable development is now high on the global agenda, but there is still a considerable degree of uncertainty in its definition, let alone implementation. The aim of this paper is to reappraise the provision of urban drainage services in the light of this current debate. The approach advocated is not to strive for the unattainable goal of completely sustainable drainage, rather to actively promote 'less unsustainable' systems. To do this requires both an understanding of the long-term and widespread impacts of continuing currentpractices and an understanding of the implications of making changes. Sustainable urban drainage should: maintain a good public health barrier, avoid local or distant pollution of the environment, minimise the utilisation of natural resources (e.g. water, energy, materials),and be operable in the long-term and adaptable to future requirements. Three strategies are proposed that can be carried out immediately,incrementally and effectively and these are to reduce potable water 'use ', to reduce and then eliminate the mixing of industrial wastewater with domestic waste, and to reduce and then eliminate the mixing of stormwater and domestic wastewater. A number of techniques are described which may allow adoption of these strategies, many of them small-scale, source control technologies. An incremental approach containing both high-tech and low-tech answers to appropriate problems is the most likely to be implemented but each case must be decided on itsmerits. [ABSTRACT FROM AUTHOR]