فهرست مطالب ایمان مصلحی

Water supply networks are considered as critical infrastructures in urban systems, the use of which has always been associated with many challenges. In these networks, the problems such as pipe breaks, water leakages and, non-uniform distribution of nodal pressures are considered as frequent challenges. In this study, a time-based scheduling approach for the use of pressure control equipment in the water network has been presented. In this regard, two operational scenarios consisting of simultaneous use of individual pressure reducing valves in the first scenario (individual scenario) and the hybrid use of pressure reducing valves with a variable speed pump in the second scenario (hybrid scenario) have been investigated. In this case, Operational programs have been developed with the aim of achieving the benefits of pressure management based on providing minimum temporal and spatial pressure variations, using a genetic algorithm as an optimization tool. Finally, the proposed strategies based on dual scenarios were validated in the context of a theoretical network as well as a real network. The optimal scenario was determined by calculating the hydraulic evaluation indicators of the network. The results show that the simultaneous use of pressure reducing valves with a variable speed pump (hybrid scenario), has been more effective in reducing pressure variations and increasing desired pressure coverage, in comparison with the individual scenario.

Water supply networks are directly related to the economic and social development of urban communities. Due to the rapid increase in population and urbanization, these networks should be properly maintained and rehabilitated. In this paper, an unsupervised learning method with OPTICS density-based clustering algorithm is used to determine the priority areas for rehabilitation. 361 burst event data in one of the Mashhad water network zones were analyzed. The algorithm identified a total number of 16 clusters at 5 different levels of importance. These 16 clusters, which are considered sub-clusters for higher levels, were compared in terms of burst rate. Three clusters with failure rates of 79.1, 62.2, and 50.1 (failures/100 km/year) were introduced as the main priorities for rehabilitation and renovation, respectively. The average burst rate in the whole network was 14.8. The identified clusters were examined in terms of pipe material and diameter and their most affecting factors on the burst rate. The obtained results showed that the OPTICS clustering algorithm has a significant ability to determine priority zones for the rehabilitation plan, by identifying multiple clusters and their according levels. Therefore, the proposed method can be used as a practical and flexible tool to prioritize the rehabilitation process of water networks and identify the main causes of failure events, avoiding complex computational methods or the personal judgment of experts.

As the main component of real water losses, leakage afflicts most water networks worldwide; even the best Water Distribution Networks (WDNs) have leakage in their network infrastructure. Several methods and strategies have been developed for leakage reduction and performance improvement in WDNs. In practice, leakage control strategies, including active leakage control, passive leakage control, pressure management, and infrastructure asset management, are performed by water utilities to reduce leakage. The main question is, which of these leakage management strategies are the most appropriate for a specific WDN? The answer to this question is obtained by analyzing the economic level of leakage (ELL). In fact, the essential component of a leakage control strategy is that its target is set in terms of the economic level of leakage (ELL). This paper provides a comprehensive review of the estimation of the ELL at different time frames, including short-run, long-run, and sustainable in WDNs. In addition, a procedure to estimate the ELL is proposed according to the conditions in each network or the relevant water utilities. Results of this review could be a valuable reference resource for practitioners and researchers dealing with non-revenue water in WDNs.

Minimum Night Flow (MNF) analysis in District Metered Areas (DMAs) is the most important method for monitoring and estimating the leakage volume in Water Distribution Networks (WDNs). An estimation of night leakage in a DMA is calculated by deducting legitimate night consumption from MNF. Therefore, the amount of household night water consumption is a crucial parameter in determining the leakage level in WDNs. The household night water consumption may be different in various countries or even in different utilities within a country. Therefore, a precise estimation of household night water consumption and use appropriate techniques are required to determine the volume of physical losses using MNF analysis. The present paper provides a literature review on analysis methods for estimating household night water consumption in different countries, their estimated values, and the effective parameters on the per capita household night consumption. This review could be used by practitioners and researchers dealing with estimating leakage level in WDNs.

Pressure management (PM) is one of the most effective methods of leakage management in water distribution networks (WDNs). In addition to reducing leakage, it provides many benefits for water utilities. The purpose of this paper is an economic analysis of the PM through a comprehensive cost-benefit analysis, taking into account the various aspects of the implementation of PM in WDNs. For this purpose, a mathematical model was developed for evaluating the benefits arising from implementing PM on the reduction of leakage, pipe breaks, active leakage control, water consumption, energy consumption, building damages and the increase of customer satisfaction and the costs of purchase, installation, operation and maintenance, and revenue reduction due to the reduction of water consumption. Using the developed model, the net benefit and benefit/cost ratio can be calculated for each PM scheme. As a case study, the advanced PM system was implemented through the installation of time modulated (TM) and flow modulated (FM) pressure reducing valves (PRVs) in a district metered area (DMA) located in Mashhad city. The net benefit and benefit/cost ration was then estimated by the developed mathematical model. The results showed that the net benefit of PM system through FM is greater than TM and the benefit/cost ratio was obtained 3.7 and 3.2 respectively. The developed mathematical model will assist water managers and practitioners in comprehensive understanding of the benefits and economic justification for implementing PM schemes.

One of the main responsibilities of water and wastewater companies in the field of operating of water distribution networks (WDNs) is the management and control of leakage from these networks. In this regard, active leakage control (ALC) is one of the main strategies in reducing leakage and achieving economic level of leakage (ELL). In this paper, a practical methodology was developed to determine the ELL which is included the steps determining the points of pressure and flow rate measurements, collecting of required field data and cost data, the estimation of leakage level in the network and the determination of the ELL of the network based on the ALC strategy. Economic performance indicators such as the economic leakage index (ELI) and the economic network efficiency (ENE) are also obtained using the determined ELL. The developed methodology was applied for a district of the WDN of Mashhad. The results showed that the ELL in the study area is 27.5 m3/connection/year. While the current level of leakage was estimated to be around 49.2 m3/connection/year, based on the minimum night flow (MNF) analysis. Moreover, the ELI and ENE were calculated 1.79 and 56% respectively. The developed methodology in this paper can assist practitioners and managers of water and wastewater companies for target-setting of the level of leakage and determining of the ELL based on it.

Anomaly or outlier detection of flow data in water distribution networks (WDNs) is implemented in data preparation and prepossessing step to achieve reliable historical data; it is important to improve the leakage assessment and management methods and the operations of the network efficiently. The main objective of this paper is to develop a new methodology based on unsupervised learning methods for anomaly or outlier detection in a flow data set in WDNs. The developed methodology includes three steps 1- required data acquisition, 2- data validation and normalization, and 3- anomaly or outlier detection using the density-based spatial clustering of application with noise (DBSCAN) algorithm. The proposed methodology is applied for inflow data into an area in Tehran's urban water distribution network with 15-min sampling intervals for 1394. The results showed that the developed methodology is capable to the detection anomalies due to different type of pipe breaks and unusual legitimate consumption such as water usage due to changes in water consumption pattern or unauthorized consumption. Therefore, this methodology can be used as an applicable and flexible tool for monitoring flow data and detecting and eliminating of different types of outliers from them.

One of the challenges facing water and wastewater companies around the world is water loss from water distribution networks following burst pipes and leakage, which imposes high economic, social and environmental costs on these companies. So, every year a large part of the budget of water and wastewater companies is allocated for the repair and rehabilitation of the pipe network. Therefore, knowing the frequency of burst pipes will help in estimating network leakages and selecting appropriate management strategies for dealing with these. Various factors affect the failure of water distribution pipes, one of the most important being water pressure. Therefore, the development of models to predict failure based on effective factors precisely is necessary to achieve optimal leakage management in water distribution networks. In the present study, using a developed model and analysis of pressure and burst field data in the urban water distribution network, the relationship between pressure and burst rate has been determined for a district of Tehran. The study area has 516 km of mains pipelines that include many types of material such as polyethylene, ductile iron, steel, PVC and asbestos cement. Both polyethylene and ductile iron pipes were selected for the investigation because they comprise 93 percent of the network length. After collecting and revising the statistics and information about the bursts and pressures recorded during the years 1386 to 1395, we have calculated the average zone point and the pressure index at this point and assigned it to the whole area. Finally, the pressure-burst relationship was presented individually for each material in the pipes. The prediction model of the failure consists of two parts, namely independent and dependent parts, through which the pressure parameter is linked through a power component to the failure rates. In this study, the maximum daily pressure at the average zone point was used as a pressure index in the pressure-burst relationship. The pressure-burst relationship for polyethylene and ductile iron based on maximum the daily pressure index is presented separately. In the relationships obtained for comparison, both the average of maximum daily pressure and the maximum of maximum daily pressure values were used. The results of this study showed that, in the dependent pressure part, the average of the maximum daily pressure index presents a more accurate result compared with the maximum value of the maximum daily pressure index and has a higher correlation coefficient. The reason for the inappropriateness of the maximum value of the maximum daily pressure can be temporary and non-permanent overload in one or more days of the year. As it may not really have caused a failure but has been involved in the calculation, this index does not have an accurate prediction of burst. Also, the relations are obtained for two conditions with a power pressure of 3 and an unknown situation, which indicates that, in the case of unknown power, higher correlation coefficients are obtained. Thus, for polyethylene the power is equal to 3 and the correlation coefficient = 0.97, while for ductile iron, the power was equal to 2.7 and the correlation coefficient = 0.99. According to the relationships obtained, it can be concluded that the pressure-burst model could predict the number of failure of main pipes in the water distribution networks well. The results also showed that pressure variations more often affect burst frequency in the polyethylene than the ductile iron pipes. The exponent of pressure in the failure prediction model also depends on the pipe material and is larger for polyethylene in comparison with ductile iron material, and the average for the maximum daily pressure index was a more accurate indicator in the failure prediction model. According to the results of this paper, we can improve pressure management and rehabilitation strategies for the reduction in burst frequency. By applying accurate pressure management and awareness of material susceptibility to burst, it is possible to reduce failure rate and, consequently, water loss.

Besides reducing leakage and consumption, pressure management affects occurrence of new bursts in water supply systems. Over the past two decades, several researchers throughout the world have studied the benefits of pressure management on reduction in the burst frequencies. During this period a wide assortment of empirical models have been developed to determine pressure-burst relationships such as pressure-leakage relationships. This paper aims to conduct a comprehensive review of these studies, relationships and empirical models pertaining to the effects of pressure management on the break rates of pipes in water supply systems. For this purpose, the developed relationships and empirical models by various researchers over the last twenty years were discussed and the advantages and disadvantages of them were summarized. Based on the review, the better understand of pressure- burst relationships could be founded and the results could be used in the analysis and evaluation of pressure management schemes in water supply systems.