Elad Salomons

Battle of the Water Networks II

The Battle of the Water Networks II (BWN-II) is the latest of a series of competitions related to the design and operation of water distribution systems (WDSs) undertaken within the Water Distribution Systems Analysis (WDSA) Symposium series. The BWN-II problem specification involved a broadly defined design and operation problem for an existing network that has to be upgraded for increased future demands, and the addition of a new development area. The design decisions involved addition of new and parallel pipes, storage, operational controls for pumps and valves, and sizing of backup power supply. Design criteria involved hydraulic, water quality, reliability, and environmental performance measures. Fourteen teams participated in the Battle and presented their results at the 14th Water Distribution Systems Analysis conference in Adelaide, Australia, September 2012. This paper summarizes the approaches used by the participants and the results they obtained. Given the complexity of the BWN-II problem and the innovative methods required to deal with the multiobjective, high dimensional and computationally demanding nature of the problem, this paper represents a snap-shot of state of the art methods for the design and operation of water distribution systems. A general finding of this paper is that there is benefit in using a combination of heuristic engineering experience and sophisticated optimization algorithms when tackling complex real-world water distribution system design problems

Conjunctive optimal scheduling of pumping and booster chlorine injections in water distribution systems

This article extends previous work on optimal booster chlorination injection design and operation in water distribution systems by solving the scheduling problem of pumping units in conjunction with the design and operation problem of booster chlorination stations. Two models are formulated and solved using a genetic algorithm scheme tailor-made to EPANET: Min Cost—for minimizing the costs of pumping and the chlorine booster design and operation, and Max Protection—for maximizing the system protection by maximizing the injected chlorine dose. An example application is explored through a base run and sensitivity analysis showing that the algorithm proposed is robust and reliable, and that the pump and chlorine injection scheduling are mutually connected.

Sensor Network Design Proposal for the Battle of the Water Sensor Networks (BWSN)

This study presents a multiobjective solution approach to the Battle of the Water Sensor Networks (BWSN) initiative (Ostfeld et al., 2006). The developed methodology tailors the algorithm of Ostfeld and Salomons (2005) for optimally placing sensors in a water distribution system with the NSGA-II multiobjective genetic algorithm of Deb et al. (2002). Pareto optimal fronts are shown and discussed for the two BWSN Networks, for selected BWSN cases. Introduction During the last decade there has been an increasing interest in development of sensor networks to cope with both deliberate and accidental hazards intrusions into water distribution systems. Optimization models and solution algorithms have been developed for sensors locations using various algorithms and objectives. These optimization models have made simplifying assumptions about design objectives, network contaminant transport, sensor response, event detection, emergency response, installation and maintenance costs, etc. Little is known about how these design algorithms compare to the efforts of human designers, and thus what advantages they propose for practical design of sensor networks. To explore these issues the Battle of the Water Sensor Networks (BWSN) initiative was called upon (Ostfeld et al., 2006) with the purpose of objectively comparing the performance of contributed sensor network designs of different teams, as applied on two water distribution system examples. This manuscript summarizes such an effort.

Optimal early warning monitoring system layout for water networks security: inclusion of sensors sensitivities and response delays

Drinking water utilities around the world are vulnerable to various types of terrorist attacks including warfare contamination and bioterrorism. A distribution system comprises water tanks, pipes, pumps, and other components that deliver treated water from treatment plants to consumers. Particularly among large utilities, distribution systems may contain thousands of kilometers of pipes and numerous delivery points, which can be highly vulnerable to a terrorist deliberate contamination injection. This paper extends previous work on optimal early warning monitoring system layout for water networks security by addressing the monitoring stations detection sensitivities and response delays, and the consumer demands and contaminant injected flow rates randomness. The methodology developed is demonstrated on two example applications.

Optimal operation of multiquality water distribution systems: unsteady conditions

This paper describes the methodology and application of a genetic algorithm scheme tailor-made to EPANET, for optimizing the operation of a water distribution system under unsteady water quality conditions. The water distribution system consists of sources of different qualities, treatment facilities, tanks, pipes, control valves, and pumping stations. The objective is to minimize the total cost of pumping and treating the water for a selected operational time horizon, while delivering the consumers the required quantities at acceptable qualities and pressures. The decision variables for each of the time steps that encompass the total operational time horizon include: the scheduling of the pumping units, settings of the control valves, and treatment removal ratios at the treatment facilities. The constraints are: head and concentrations at the consumer nodes, maximum removal ratios at the treatment facilities, maximum allowable amounts of water withdrawals at the sources, and returning at the end of the operational time horizon to a prescribed total volume in the tanks. The model is explored through two example applications.

Characterizing Cyber-Physical Attacks on Water Distribution Systems

AbstractThis work contributes a modeling framework to characterize the effect of cyber-physical attacks (CPAs) on the hydraulic behavior of water distribution systems. The framework consists of an ...

An Early Warning Detection System (EWDS) for Drinking Water Distribution Systems Security

Since September 11, 2001 the US EPAs water protection task force and regional offices have initiated massive actions to improve the security of drinking water infrastructure. This paper deals with the development and application of a methodology for finding the optimal layout of a detection system, taking explicitly into account the unsteady hydraulics, and the dilution and decay properties of the water quality constituents as distributed with flow. The detection system outcome is a set of monitoring stations aimed at capturing contaminant entries within a pre-specified level of service, defined as the maximum volume of polluted water exposure to public at a concentration higher than a minimum hazard level. The detection system provides an early warning system for a deliberate terrorist external hazard intrusion – a problem that currently has not been solved. The methodology is casted in a genetic algorithm framework tailored made with EPANET. An example application for Anytown U.S.A. is provided.

A sensitive biomarker for the detection of aquatic contamination based on behavioral assays using zebrafish larvae.

An effective biological early warning system for the detection of water contamination should employ undemanding species that rapidly react to the presence of contaminants in their environment. The demonstrated reaction should be comprehensible and unambiguously evidential of the contamination event. This study utilized 96h post fertilization zebrafish larvae and tested their behavioral response to acute exposure to low concentrations of cadmium chloride (CdCl2) (5.0, 2.5, 1.25, 0.625mg/L) and permethrin (0.05, 0.029, 0.017, 0.01μg/L). We hypothesize that the number of larvae that show advanced trajectories in a group corresponds with water contamination, as the latter triggers avoidance behavior in the organisms. The proportion of advanced trajectories in the control and treated groups during the first minute of darkness was designated as a segregation parameter. It was parametrized and a threshold value was set using one CdCl2 trial and then applied to the remaining CdCl2 and permethrin replicates. For all cases, the method allowed distinguishing between the control and treated groups within two cycles of light: dark. The calculated parameter was statistically significantly different between the treated and control groups, except for the lowest CdCl2 concentration (0.625mg/L) in one replicate. This proof-of-concept study shows the potential of the proposed methodology for utilization as part of a multispecies biomonitoring system.

New formulation and optimization methods for water sensor placement

Optimal sensor placement for detecting contamination events in water distribution systems is a well explored problem in water distribution systems security. We study herein the problem of sensor placement in water networks to minimize the consumption of contaminated water prior to contamination detection. For any sensor placement, the average consumption of contaminated water prior to event detection amongst all simulated events is employed as the sensing performance metric. A branch and bound sensor placement algorithm is proposed based on greedy heuristics and convex relaxation. Compared to the state of the art results of the battle of the water sensor networks (BWSN) study, the proposed methodology demonstrated a significant performance enhancement, in particular by applying greedy heuristics to repeated sampling of random subsets of events. Mixed integer convex programming (MICP) for sensor placement.Branch and bound for finding the global optimum of the MICP.Competitive comparison to the battle of the water sensor networks.Branch and bound algorithm based on convex relaxation and a greedy heuristic.Implementation capability on real sized water networks.

Solving the Inverse Problem of Deliberate Contaminants Intrusions into Water Distribution Systems

A methodology is developed and applied for solving the general inverse problem of a deliberate contaminant intrusion into a water distribution system: given a contaminant detection at one or more online monitoring/sensors stations—identify the injection characteristics: (1) location, (2) starting time, (3) intensity (mass time), and (4) duration. The algorithm is based on the randomized pollution matrix (RPM) concept, developed in previous works by the authors, and taking into account the monitoring stations detection sensitivity, their response delay, and possible different injection probabilities throughout the system. The model outcomes are the system nodes with the highest likelihood to be the injection locations; the approximated injection starting times; intensities; and durations. The model is demonstrated through a base run and sensitivity analysis using a simple example application.