Armando Di Nardo

A heuristic design support methodology based on graph theory for district metering of water supply networks

The management of existing water supply networks can be substantially improved by permanent water district metering (WDM) which is one of the most efficient techniques for water loss detection and pressure management. However, WDM may compromise water system performance, since some pipes are usually closed to delimit districts in order not to have too many metering stations, to decrease costs and simplify water balance. This may reduce the reliability of the whole system and not guarantee the delivery of water at the different network nodes. In practical applications, the design of district meter areas (DMAs) is generally based on empirical approaches or on limited field experiences. In this work a design support methodology (DSM) is proposed, which helps to identify the position of flow meters and of boundary valves needed to define permanent DMAs. The DSM is based on graph theory and is applied to a test case.The management of existing water supply networks can be substantially improved by permanent water district metering (WDM) which is one of the most efficient techniques for water loss detection and pressure management. However, WDM may compromise water system performance, since some pipes are usually closed to delimit districts in order not to have too many metering stations, to decrease costs and simplify water balance. This may reduce the reliability of the whole system and not guarantee the delivery of water at the different network nodes. In practical applications, the design of district meter areas (DMAs) is generally based on empirical approaches or on limited field experiences. In this work a design support methodology (DSM) is proposed, which helps to identify the position of flow meters and of boundary valves needed to define permanent DMAs. The DSM is based on graph theory and is applied to a test case.

Water Network Sectorization Based on Graph Theory and Energy Performance Indices

AbstractThis paper proposes a new methodology for the optimal design of water network sectorization, which is an essential technique for improving the management and security of multiple-source water supply systems. In particular, the network sectorization problem under consideration concerns the definition of isolated district meter areas, each of which is supplied by its own source (or sources) and is completely disconnected from the rest of the water system through boundary valves or permanent pipe sectioning. The proposed methodology uses graph theory principles and a heuristic procedure based on minimizing the amount of dissipated power in the water network. The procedure has been tested on two existing water distribution networks (WDNs) (in Parete, Italy and San Luis Rio Colorado, Mexico) using different performance indices. The simulation results, which confirmed the effectiveness of the proposed methodology, surpass empirical trial-and-error approaches and offer water utilities a tool for the desi...

An Automated Tool for Smart Water Network Partitioning

Water Network Partitioning (WNP) represents the application of the “divide and conquer” paradigm to a Smart WAter Network (SWAN) that allows the improved application of techniques for water balance and pressure control. Indeed, these techniques can be applied with greater effectiveness by defining smaller permanent network parts, called District Meter Areas (DMAs), created by the insertion of gate valves and flow meters. The traditional criteria for the design of network DMAs are based on empirical suggestions (number of properties, length of pipes, etc.) and on approaches such as ‘trial and error’, even if used together with hydraulic simulation software. Nevertheless, these indications and procedures are very difficult to apply to large water supply systems because the insertion of gate valves modifies the original network layout and may considerably worsen the hydraulic performance of the water network. The proposed tool, based on some graph partitioning techniques, commonly applied in distributed computing, and on an original optimisation technique, allows the automatic design of a WNP comparing different possible layouts that are compliant with hydraulic performance. In this paper, the methodology was tested on a real case study using some performance indices to compare different WNPs. The proposed tool was developed in Phyton and integrates graph partitioning, hydraulic simulation techniques and a heuristic optimisation criterion. It allows the definition of DMAs with resulting performance indices that are very similar to the original network layout.

Water Network Protection from Intentional Contamination by Sectorization

Each single phase of a water supply network, from water adduction to distribution to end-users, is exposed to many diverse potential sources of intentional contamination (or malicious attacks). One of the most dangerous threats is a backflow attack that occurs when a pump system, easily available on the market, is utilized to overcome the pressure gradient of network pipes. In this work, a simple backflow attack with cyanide being introduced into a real-water system is modeled and the most dangerous introduction points for a contaminant incident are defined. Moreover, the network vulnerability has been analyzed by computing the lethal dose of cyanide ingested by users and the total length of the contaminated water system. Eventually the effects of network partitioning and district isolation to protect water supply systems have been investigated. The results show how district closing - by network sectorization techniques used to improve leakage search and reduction - can significantly decrease contaminant diffusion and protect part of the users from cyanide uptake. Network sectorization can also reduce the risk of simple malicious attacks because several introduction points are necessary to have a massive negative impact on the network. Simulation results also show that in some cases water network partitioning may worsen water network protection and further studies are necessary to design water districts for network security and safety.

A DESIGN SUPPORT METHODOLOGY FOR DISTRICT METERING OF WATER SUPPLY NETWORKS

Water District Metering (WDM) is one of the most efficient techniques for water loss detection and pressure management and consists in partitioning a water network into subsystems called District Meter Areas (DMA).The division of the network in hydraulically independent districts can be obtained by installing flow meters and boundary valves. Pipe closure can compromise original water system performance because it reduces the network reliability. When water systems are already in operation it is more difficult to set the number and dimension of districts and, in practical applications, the WDM design is generally based on empirical approaches or on limited field experiences. In this work an original approach to define the Water District Metering, based on graph theory principles, is put forward. The methodology proposed, arranged in a Design Support Methodology (DSM), allows to choose the position of flow meters and of boundary valves needed to define permanent DMAs using graph visualization of water network, minimum dissipated power paths and different performance indices based also on resilience concept. The DSM is tested on two case studies allowing to get rapidly good DMA layouts compatible with the level of service of water systems.

Permeable reactive barrier for groundwater PCE remediation: the case study of a solid waste landfill pollution

The remediation of a tetrachloroethylene (PCE) contaminated aquifer near a solid waste landfill, by an activated carbon Permeable Reactive Barrier (PRB) is presented as a case study. A 2D numerical model has been used to describe the pollutant transport within a groundwater and the pollutant adsorption on the barrier. The results show that the barrier has a good efficiency since the PCE concentration flowing out of the PRB is always lower than the limits provided for in the currently enforced Italian legislation.

Water Supply Network Partitioning Based On Weighted Spectral Clustering

Water Network Partitioning (WNP) in District Meter Area (DMA), obtained inserting remote control valves and flow meters in water supply systems, allows simplifying the water balance and pressure control in order to reduce water leakage and to improve water quality protection. Traditionally, the WNP is based on empirical suggestions and on trial and error approaches used with hydraulic simulation software, difficult to apply to large networks. Recently, some heuristic procedures, based on graph and network theory, have shown that it is possible to find optimal solutions in terms of number, shape and dimension of DMAs. In this paper, spectral clustering theory was used to define the water districts, taking into account the spatial and hydraulic constraints, through weight matrices. A comparison between different spectral clustering methods was achieved on a real water network measuring some energy performance indices, in order to identify the optimal water network partitioning.

Scaling-Laws of Flow Entropy with Topological Metrics of Water Distribution Networks

Robustness of water distribution networks is related to their connectivity and topological structure, which also affect their reliability. Flow entropy, based on Shannon’s informational entropy, has been proposed as a measure of network redundancy and adopted as a proxy of reliability in optimal network design procedures. In this paper, the scaling properties of flow entropy of water distribution networks with their size and other topological metrics are studied. To such aim, flow entropy, maximum flow entropy, link density and average path length have been evaluated for a set of 22 networks, both real and synthetic, with different size and topology. The obtained results led to identify suitable scaling laws of flow entropy and maximum flow entropy with water distribution network size, in the form of power–laws. The obtained relationships allow comparing the flow entropy of water distribution networks with different size, and provide an easy tool to define the maximum achievable entropy of a specific water distribution network. An example of application of the obtained relationships to the design of a water distribution network is provided, showing how, with a constrained multi-objective optimization procedure, a tradeoff between network cost and robustness is easily identified.

Optimal Fuzzy Management of Reservoir based on Genetic Algorithm

This chapter deals with water resource management problems faced from an Automatic Control point of view. The motivation for the study is the need for an automated management policy for an artificial reservoir (dam). A hybrid model of the reservoir is considered and implemented in Stateflow/Simulink, and a fuzzy decision mechanism is implemented in order to produce different water release strategies. A new cost functional is proposed, able to weight user’s desiderata (in terms of water demand) with water waste (in terms of water spills). The parameters of the fuzzy system are optimized by employing Genetic Algorithms, which have proved very effective due to the strong nonlinearity of the problem. Modi- fied AR and ARMAX models of the inflow are identified and Montecarlo simulations are used to test the effectiveness of the proposed strategy in different operating scenarios.

AN OPTIMAL FUZZY APPROACH TO AUTOMATED RESERVOIR MANAGEMENT

Abstract This paper deals with water resource management problems faced from an Automatic Control point of view. The motivation for the study is the need for an automated management policy for an artificial reservoir (dam). Two problems are addressed in the article: the control of the dam gate, that is a typical control problem, and the definition of the water flow to supply to the user, that is a decision problem. In particular, a mathematical model of the reservoir is deduced, and a PID controller with fuzzy (nonlinear) gains is designed to operate the dam gate. Moreover, a hybrid model of the reservoir is considered and implemented in Stateflow/Simulink, and a second fuzzy decision mechanism is implemented in order to produce different water release strategies. A new cost functional is proposed, able to weight users desiderata (in terms of water demand) with water waste (in terms of water spills). The parameters of the fuzzy system are optimized by employing Genetic Algorithms, which have proved very effective due to the strong nonlinearity of the problem.