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Technical Performance Assessment of Urban Sewer Systems
Abstract
Performance assessment in urban water infrastructures is an increasingly important field of knowledge. Performance has traditionally been expressed in a variety of ways relating mostly to local design practice, with hardly any consensus on how it should be measured or compared. The efficient technical management of these systems deserves a specific approach, suited to the methodologies regularly employed while planning, designing, constructing, operating, and maintaining the systems. At the engineering level, decisions are based on operational, physical, and resources data and on analyses deploying simulation models, geographic information systems, or other information systems. However, such tools tend to produce vast amounts of insufficiently aggregated or performance-oriented information. This paper presents a performance assessment system that is based on the decisional concept of utility functions and designed as a technical analysis tool with the purpose of shifting the focus of technical management of urban drainage systems to a performance-oriented view.
... Performance modelling involves computing of indicators based on hydraulic modelling and asset modelling. Hydraulic KPI – wet weather flow Hydraulic modelling is used to assess system performance in terms of Dry Weather Flows (DWF),Wet Weather Flows (WWF) and sedimentation.A major operational concern for urban drainage systems is their performance under WWF and especially the onset of hydraulic incapacity in system and any resultant flooding.This issue is being approached by reference to a series of design events with a range of return periods with the ability to alter the duration of the events.The proposed performance measure for hydraulic incapacity under WWF is based on a modified performance assessment system (Cardoso et al, 2002) expressed either in terms of discharge (Q) or water level (H) (hydraulic head), Figure 3shows this in terms of water level.The Hydraulic KPI (HKPI) is considered to be satisfactory (100%) for water levels up to a certain value H* below pipe soffit (pipe nearly full) which corresponds to discharges up to Q* (Q* smaller than the full pipe flow), falling to X% at surcharging (full pipe flow), and further falling to 0% when hydraulic head reaches the ground level and flow rate reaches some Qflood (start of flooding).This function represents different levels of performance of an asset under WWF: satisfactory / acceptable / nonacceptable , at a moment in time.The extent of incapacity or flooding is introduced by computing a 1-hour moving average of HKPI, i.e. by averaging over the 'worst' one hour, for a rainfall event – hence, flooding that took place for 15 minutes with a moderate flood volume would still result in some small positive KPI value, whereas only flooding longer than one hour would give zero KPI. For one return period, this is done for a series of design events so that critical storm duration (ie, the one which gives smallest KPI) is used for each pipe. ...
... Coelho (1997b) presents a TPI to evaluate water quality performance. TPIs have been also used in other research domains: urban sewer systems (Cardoso et al., 2005), evaluation of the effect of pressure dependent analysis on quality performance assessment of WDNs (Tabesh and Dolatkhahi, 2006); evaluation of the WDNs performance for different pipe materials (Tamminen et al, 2008;Ramos et al., 2009); assessment of the operational performance of water treatment plants (Vieira et al., 2010); among others. ...
This paper explores the use of Technical Performance Indexes (TPIs) to assess the operational performance of Water Distribution Networks (WDNs) and exemplifies its suitability to easily identify problematic zones. The paper also points out some problems associated with the existent TPIs and proposes new analysis tools to avoid these difficulties. These new analysis tools (such as state variable slack and constraint violation) are conjugated with the pressure-driven simulation model for illustration purposes, including operational performance assessment during pipe bursts or firefighting scenarios, and to identity and account for the “demand not satisfied” due to those events.
... Under wet weather conditions, a development of the performance assessment system described by Cardoso et al (2002) has been proposed, this would be expressed in terms of either water level or discharge, a diagrammatic representation for the performance function in terms of water level is shown in Figure 3. The hydraulic performance functions would be calculated for each of the WWF design events and for each asset a series of performance indicators produced. ...
The UK water industry faces a need to manage sewer systems to meet and maintain required levels of service in a cost effective manner whilst minimising social and environmental impacts. Whole life costing approaches have been shown to provide an ideal platform for the evaluation of such a system by taking account of system behaviour, performance and regulation within a sensible economic and engineering framework. Combined with a decision support tool, the whole life costing approach has the potential to provide optimised solutions for sewer system management.
... This issue is being approach by reference to a series of design events with a range of return periods with the ability to alter the duration of the events. The proposed performance measure for hydraulic incapacity under Wet Weather Flows (WWF) is based on a modified performance assessment system (Cardoso et al, 2002) expressed either in terms of discharge (Q) or water level (H) (hydraulic head), Figure 3shows this in terms of water level. The value H* (or Q*) represents the required or acceptable level of performance of an asset under WWF, with values dependent on pipe size, category, condition grade and possibly other factors. ...
... In this scenario, the hourly velocity performance for the entire network velocity conditions of the system was evaluated by means of HAM and the results are shown inFig. 2. The importance of performance assessment has been growing in the planning, design, installation, and operation of sewer systems, which can not only lead to a better knowledge of the utility's activities but also is a suitable basis for the diagnosis, control and selection of solutions for the improvement of technical process and system performance (Cardoso et al., 2005). Low velocities can cause sediment and solids deposition, thus flow velocity is the crucial hydraulic performance variable and selected as the performance indicator to evaluate the deposition risk of sewer systems. ...
Severe operational problems of sediment deposition have frequently occurred in stormwater sewer systems in Shanghai city due
to the flat topography of the area and serious illicit connections. To control sewer sediment and its subsequential problems,
optimized operation plans were proposed and an innovative performance assessment method was developed. Simulation results
demonstrated that, through changing the way of pump operation and installing necessary actuators in the system, the optimized
operations, especially batch intermittent intercept plan, effectively improved the flow velocity in the entire system in dry-weather
condition. In conclusion, the optimized operation is an innovative idea for improving the performance and solving the problem
of sediment deposition in the sewer system in Shanghai, China.
Key wordsSewer system-Sediment control-Performance assessment-Simulation
CLC numberTU992.4
... Numerical integrated modelling became a standard procedure to optimise urban wastewater systems management and operation (Rauch et al., 2002;Erbe et al., 2002;Schütze et al., 2002). Performance assessment is also an increasingly important field of knowledge (Cardoso et al., 2005;Saegrov, 2006;Murray et al., 2009) viewed has an integrated management tool useful for rehabilitation planning, in order to prioritise areas of intervention in a decisionmaking context as well as to assess the performance benefits of each intervention. Substance flow analysis (SFA), combined with mass balances, is another tool to perform sewer systems analysis that has proved to be appropriate to highlight pressures on the receiving waters and to pinpoint information gaps (Benedetti et al., 2008). ...
Although the application of complex integrated models to wastewater systems is useful, it is often difficult to implement and not always suitable for the design of new systems or for their rehabilitation. Integrated simple approaches that allow assessing the environmental performance of urban wastewater systems may be advantageous, especially during the initial phases of the system planning process. This paper presents an original, straightforward approach that can be used for planning, design and operation of urban wastewater systems. The INtegrated Simplified Approach (INSA) combines the concepts of performance indicators with mass balances and can be applied to wastewater systems as a management support tool, particularly in situations where there is lack of data, economic limitations or time constraints. The INSA was applied to the Algés-Alcântara wastewater system to evaluate its environmental performance and to simulate the individual or combined impact of the rehabilitation measures proposed, thus defining their priority. The results clearly indicate that, despite the investment already made upgrading the wastewater treatment plant (WWTP), the proposed interventions must be implemented to ensure an acceptable environmental performance of the system. In addition, the results demonstrate the significant pollution loads present in stormwater, frequently higher than the pollution loads discharged into receiving waters during dry weather.
O crescimento populacional, a escassez de água, a deterioração das tubulações e estruturas são alguns dentre muitos desafios enfrentados por empresas de abastecimento de água. Nesse sentido, a avaliação de desempenho torna-se fundamental para priorizar ações de aperfeiçoamento e, via de consequência, potencializar resultados em tais companhias. Esta pesquisa, de natureza exploratória-descritiva, teve como objetivo selecionar e identificar artigos de forma estruturada sobre o tema “Avaliação de Desempenho em Sistemas de Abastecimento de Água” por meio do Knowledge Development Process – Constructivist (Proknow-C). Foram encontrados 949 artigos brutos em 6 bases de dados do Portal de Periódicos da Capes, os quais após a filtragem prevista no Proknow-C, resultaram em 19 artigos que compuseram o Portfólio Bibliográfico (PB) com 68 referências. Na análise bibliométrica foi observado como periódico de maior destaque o Water Policy. Os autores de maior destaque foram H. Ramos, R. C. Marques, S. Sharma, K. Vairavamoorthy e H. E. Mutikanga. O artigo com maior reconhecimento bibliográfico foi Efficiency measurement in Australian local government: The case of New South Wales municipal water services, de K. Woodbury e B. Dollery, com 42 citações. As palavras-chave mais relevantes para o tema foram: Performance indicators, Water supply systems, Asset management, Performance evaluation e Water Utilities, consideradas na pesquisa inicial.
Drainage networks are generally repaired after a failure occurs, and there is a lack of risk prevention and evaluation. To provide an effective evaluation method for the safe operation of drainage pipe networks, particularly in terms of pipeline failure and the severity of issues, this study classifies the adverse factors of safe operation and establishes an index evaluation system to determine the probability of pipeline failure. The system considers human, management, pipeline attribute, and environmental factors and is suitable for buried drainage pipelines. According to the index evaluation system, the analytic network process (ANP) method is used to consider the coupling relationship between various factors and obtain the weight of each factor. A fuzzy comprehensive evaluation is performed to obtain the final evaluation results. Finally, the established method is implemented on the drainage network of Suzhou Industrial Park, China. The results show that the evaluation results of this method are consistent with the daily cognition and field detection results. In addition, the index system established in this study can provide a reference for the establishment of accident databases and management of drainage networks.
This paper presents a set of performance indicators (PIs) for assessing loss of wastewater service and the induced functional impacts in three different phases: emergency response, short-term recovery and long-term restoration. Built on the experience and learning of the Stronger Christchurch Infrastructure Rebuild Team in reinstating the resilience of the Christchurch wastewater system following the Canterbury Earthquakes in 2010-2011, the developed PIs aim to evaluate holistically the structural, hydraulic, environmental, social and economic consequences that might arise due to the earthquake-induced physical damage to sewerage components. This includes sewer pipelines, pumping stations, manholes and council-owned laterals. Furthermore, a framework in which the proposed PIs are integrated into is introduced for demonstrating practical applications. The decision support framework includes three modules, namely: (a) physical damage module, (b) functional impact module and (c) serviceability restoration module. The framework is intended to support the decision-making process in terms of restoration strategy selection and resource allocation in the move towards an effective and informed reinstatement of sewerage systems after earthquakes.
Population growth, water scarcity, deteriorating pipes and structures are some challenges faced by water supply companies. Performance evaluation becomes essential to prioritize improvement actions and, as a consequence, enhance outcomes in such companies. This research, exploratory and descriptive, aimed to select and identify articles in a structured way about "Performance Evaluation in Water Supply System", through Proknow-C. After filtering process provided in Proknow-C, 19 articles were included in the Bibliographic Portfolio and 68 references of PB. In bibliometric analysis it was observed that the most prominent journal in the subject's Water Policy, and most of periodic were IWA - International Water Association publications. The most prominent authors currently are H. Ramos, R. C. Marques, S.
Sharma, K. Vairavamoorthy and H. E. Mutikanga. The most cited article was “Efficiency measurement in Australian Local government: The case of New South Wales municipal water services”, by K. Woodbury and B. Dollery, with 42 citations. The keywords most relevant to the subject were: Performance indicators, water supply systems, asset management, performance evaluation and Water Utilities, considered in the initial search. The research topic is recent, with few articles and authors with scientific recognition.
In this paper, a flexible fuzzy model is proposed for the hydraulic performance analysis of separate domestic sewer systems. In the proposed model, all modeling outputs such as discharge, velocity and depth are developed as fuzzy numbers by taking into account all the available information and expert knowledge about the basic design/analysis parameters. The fuzzy outputs are then combined with performance assessment curves to calculate the hydraulic performance values. The proposed model was applied to a part of the sewer system of a city in Iran, and performance graphs were plotted. Such graphs can be used by design engineers and operation managers to improve the design quality, reliability and the performance of a system with uncertain parameters. The analysis results can also be used in decision-making and identifying priorities to develop rehabilitation strategies.
The aim of this paper is to compare sorting and ranking methods for prioritization of rehabilitation interventions of sewers, taking into account risk, performance and cost. For that purpose multiple criteria decision-aid (MCDA) methods such as ELECTRE TRI for sorting and ELECTRE III for ranking are applied in a real case-study and the results obtained are compared. The case study is a small sanitary sewer system from a Portuguese utility located in the metropolitan area of Lisbon. The problem to investigate is the prioritization of the sewer candidates for rehabilitation. The decision maker (a panel group of specialists) has chosen five assessment measures: water level and maximum flow velocity (hydraulic performance indices), sewer importance and failure repair cost (collapse-related consequences of failure) and the risk of collapse. The results show that the outcomes from ELECTRE III are easier to understand than those from ELECTRE TRI method. Two different sets of weights were used, and the sorting and ranking results from both methods were found to be sensitive to them. ELECTRE TRI method is not straightforward as it involves technical parameters that are difficult to define, such as reference profiles and cut levels.
Metric benchmarking has been widely quoted as a powerful management tool. However, as useful as metric benchmarking can prove, its actual application may present several inconveniences. These include internal resistance to the project, difficulties in finding a suitable partner, finding an appropriate set of indicators, actual data management and results analysis. This paper will present general guidelines to carry out a metric benchmarking project within the water industry, as well as some tools that may be used to overcome some of these difficulties. Special attention is paid to the selection process of the performance indicators for the system. A specific mehod based on the cross impact analysis has been developed to provide a consistent and systematic way to reach an appropriate PI selection.
National contributions from 16 countries and additional information were used for an international state-of-the-art report on performance assessment (PA) in the water industry. The purposes of this international report are i) to discuss areas of PA within the water supply and wastewater sector, ii) to analyse aspects of practical relevance and iii) to look on future trends and developments. Several aspects of PA are discussed, such as the quality and the availability of data, the importance of definitions and explanatory factors, the use of information from PA, and practical aspects such as willingness to participate and costs. Standardised PA frameworks of the International Water Association (IWA), the World Bank, and the Water Utility Partnership are presented, and an outlook on research and development of PA tools is given.
The aim of this paper is to present current work to develop a system of performance indicators (PI) for wastewater services undertaken under the auspices of IWA and coordinated by LNEC. Present day wastewater utilities manage their services and systems in an increasingly demanding and complex way. For this reason, it is important to support their work and decision processes with the best available tools in order to deliver services with the most effective and efficient performance. The paper focuses on proposed performance indicators (PIs) for wastewater services and on the main aspects of PI assessment. These are based on data related to: environmental, operational, personnel, physical, quality of service and economic and financial performance. Data are mostly made available through the various common-use information systems in the utilities. This IWA forum has been important not only for the dissemination of the work already developed but also as promotion of a wider discussion to enhance the final draft version of the IWA Manual of Best Practice due for publication in 2003.
L'analyse de la performance est devenue tres importante pour la gestion des reseaux d'assainissement, pas uniquement comme le resultat d'une evolution naturelle des methodes de modelisation et de conception, mais egalement comme une reponse a la recherche permanente de l'amelioration du service fourni aux utilisateurs. Les indicateurs de performance constituent un outil puissant de comparaison de performances independantes ; ils peuvent etre exploites comme support pour etablir des strategies de rehabilitation et des options de gestion. Cette communication presente une methodologie systematique et standardisee d'evaluation de la performance des reseaux d'assainissement, basee sur des indicateurs de performance. Elle est illustree par une application au reseau de Laje, situe sur la zone cotiere du Portugal. L'objectif principal de ce travail est de developper un systeme d'evaluation applicable a tous les types de reseaux d'assainissement.
Performance indicators are measures of the efficiency and effectiveness of the water utilities with regard to specific aspects of the utility’s activity and of the system’s behaviour. Efficiency is a measure of the extent to which the resources of a water utility are utilised optimally to produce the service, while effectiveness is a measure of the extend to which the targeted objectives (specifically and realistically defined) are achieved. Each performance indicator expresses the level of actual performance achieved in a certain area and during a given period of time, allowing for a clear cut comparison with targeted objectives and simplifying an otherwise complex analysis. They can be applied at different levels. Within the water utility, the use of performance indicators is growing in importance as the basis for assessing the efficiency (ratio between input consumed and output achieved) and effectiveness of the utility as a whole and of its management units. Such measures can be used to trace the trend in the performance of a given unit over a period of time as well as to make performance comparisons between similar units. Within the country, performance indicators are applicable at a regional or at a national level. Within the supra-national regions, performance indicators allow for comparing different countries of the same or of different regions of the world.
Sewer maintenance and rehabilitation strategies developed in a number of countries are reviewed. Comparisons are made between those approaches that focus on a predefined subset of strategic sewers and those that consider proactive maintenance of the whole system to address the wider consequences of failure such as customer satisfaction, social disruption and environmental damage. A number of diverse methods are described which can be used to optimise and prioritise proactive maintenance by analysing sewer performance, and lessons are drawn from maintenance strategies developed for other buried infrastructure assets. Limitations in existing sewer databases are discussed and new methods of obtaining sewer condition information are described. The paper concludes that to be cost effective, proactive maintenance involving inspection and repair must be focussed on those pipes which can be shown to have an early predisposition to failure.
Performance in water distribution—A systems ap-proach
- S T Coelho
- ͑1997͒
Coelho S. T. ͑1997͒. Performance in water distribution—A systems ap-proach, Wiley, New York.
Performance analysis in water distribution Computing and control for the water industry
- S T Coelho
- P W Jowitt
- ͑1998͒
Coelho, S. T., and Jowitt, P. W. ͑1998͒. " Performance analysis in water distribution. " Computing and control for the water industry, R. Pow-ell and K. Hindi, eds., Wiley, New York, 1–19.
Drain and sewer systems out-side buildings. Part 2: Performance requirements
- Committee ͑1996͒
European Standards Committee. ͑1996͒. " Drain and sewer systems out-side buildings. Part 2: Performance requirements. " EN 752–2, Brus-sels, Belgium.
Aerobiose e septicidade em sistemas de drenagem de águas residuais
- J S Matos
Matos, J. S. ͑1992͒. " Aerobiose e septicidade em sistemas de drenagem de águas residuais. " PhD thesis, Dept. of Civil Engineering, Technical Univ. of Lisbon, Lisbon, Portugal ͑in Portuguese͒.
A new approach for diagnosis and rehabilitation of sewerage systems through the development of performance indicators
- M A Cardoso
- S T Coelho
- J S Matos
- R M Matos
Benefits of hydraulic analysis of separate domestic systems through mathematical modelling
- M A Cardoso
- M C Almeida
- R S Brito