scholarly journals Integrating evolution strategies and genetic algorithms with agent-based modeling for flushing a contaminated water distribution system

2013 ◽  
Vol 15 (3) ◽  
pp. 798-812 ◽  
Author(s):  
Emily M. Zechman
Keyword(s):  
Public Health ◽  
Distribution System ◽  
Water Distribution ◽  
Water Distribution System ◽  
Complex Adaptive System ◽  
Management Strategies ◽  
Evolution Strategies ◽  
Illustrative Case ◽  
Health Consequences ◽  
Agent Based

Water utilities can prepare for water distribution hazards, such as the presence of contaminants in the pipe network and failure of physical components. In contamination events, the complex interactions among managers' operational decisions, consumers' water consumption choices, and the hydraulics and contaminant transport in the water distribution system may influence the contaminant plume so that a typical engineering model may not properly predict public health consequences. A complex adaptive system (CAS) approach couples engineering models of a water distribution system with agent-based models of consumers and public officials. Development of threat management strategies, which prescribe a set of actions to mitigate public health consequences, is enabled through a simulation–optimization framework that couples evolutionary algorithms with the CAS model. Evolution strategies and genetic algorithm-based approaches are developed and compared for an illustrative case study to identify a flushing strategy for opening hydrants to minimize the number of exposed consumers and maintain acceptable levels of service in the network.

scholarly journals An agent-based modeling framework for sociotechnical simulation of water distribution contamination events

2013 ◽  
Vol 15 (3) ◽  
pp. 862-880 ◽  
Author(s):  
M. Ehsan Shafiee ◽  
Emily M. Zechman
Keyword(s):  
Distribution System ◽  
Water Distribution ◽  
Water Distribution System ◽  
Large Population ◽  
Water Distribution Network ◽  
Contaminant Plume ◽  
Modeling Framework ◽  
Agent Based ◽  
Water Demands ◽  
Demand Patterns

In the event that a contaminant is introduced to a water distribution network, a large population of consumers may risk exposure. Selecting mitigation actions to protect public health may be difficult, as contamination is a poorly predictable dynamic event. Consumers who become aware of an event may select protective actions to change their water demands from typical demand patterns, and new hydraulic conditions can arise that differ from conditions that would be predicted when demands are considered as exogenous inputs. Consequently, the movement of the contaminant plume in the pipe network may shift from its expected trajectory. A sociotechnical model is developed here to integrate agent-based models of consumers with an engineering water distribution system model and capture the dynamics between consumer behaviors and the water distribution system for predicting contaminant transport and public exposure. Consumers are simulated as agents with behaviors, including movement, water consumption, exposure, reduction in demands, and communication with other agents. As consumers decrease their water use, the location of the contaminant plume is updated and the amount of contaminant consumed by each agent is calculated. The framework is tested through simulating realistic contamination scenarios for a virtual city and water distribution system.

scholarly journals Sociotechnical risk assessment for water distribution system contamination threats

2013 ◽  
Vol 16 (3) ◽  
pp. 531-549 ◽  
Author(s):  
Amin Rasekh ◽  
M. Ehsan Shafiee ◽  
Emily Zechman ◽  
Kelly Brumbelow
Keyword(s):  
Public Health ◽  
Risk Assessment ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Probabilistic Models ◽  
Health Consequences ◽  
Multi Objective ◽  
Contamination Event ◽  
Contamination Events

Water distribution systems (WDS) are vulnerable to contaminants, and systematic risk assessment can provide valuable information for assisting threat management. Contamination events are sociotechnical systems, in which the interactions among consumers and water infrastructure may generate unpredicted public health consequences. This research develops a sociotechnical risk assessment framework that simulates the dynamics of a contamination event by coupling an agent-based modeling (ABM) framework with Monte Carlo simulation (MCS), genetic algorithm (GA) optimization, and a multi-objective GA. The ABM framework couples WDS simulation with agents to represent consumers in a virtual city. MCS is applied to estimate the uncertainty in human exposure, based on probabilistic models of event attributes. A GA approach is used to identify critical contamination events by maximizing risk, and a multi-objective approach explores the trade-off between consequence and occurrence probabilities. Results that are obtained using the sociotechnical approach are compared with results obtained using a conventional engineering model. The sociotechnical approach removes assumptions that have been used in engineering analysis about the static, homogeneous, and stationary behaviors of consumers, and results demonstrate new insight about the impacts of these actions and interactions on the public health consequences of contamination events.

scholarly journals Stringency of Water Conservation Determines Drinking Water Quality Trade-Offs: Lessons Learned from a Full-Scale Water Distribution System

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2579
Author(s):  
Fatemeh Hatam ◽  
Gabrielle Ebacher ◽  
Michèle Prévost
Keyword(s):  
Water Quality ◽  
Water Conservation ◽  
Distribution System ◽  
Reliability Index ◽  
Water Distribution ◽  
Water Distribution System ◽  
Demand Management ◽  
Management Strategies ◽  
Reference Scenario ◽  
Water Age

Demand variations over time affect the hydraulic and water quality behavior of water distribution systems. Therefore, it is important to assess the network performance under various future water demand scenarios to plan effectively for demand management strategies, considering the network’s topology, volume, and operational conditions. The performance of a full-scale water distribution system is evaluated by means of hydraulic and water quality simulations under different hypothetical demand management strategies. Residential and nonresidential consumptions are varied, resulting in different global multiplicative factors (from 0.53 to 1.18). Criteria including water loss, velocity, water age, free chlorine, and THMs are selected to compare the performance of the network between the current scenario and eight demand scenarios. Water conservation generally increases nodal water age values more in smaller diameter pipes. A nodal chlorine residual reliability index is proposed to account for the duration of low chlorine residuals. With a goal of maintaining a reference free chlorine concentration of ≥0.2 mg/L, the reliability index is less than 0.9 for about 14% of nodes under the reference scenario and this proportion increases to 34% of nodes under the most extreme future water conservation scenario. The robustness of the studied network under different water conservation scenarios is tested by increasing the chlorine residual at the outlet of the WTPs from 1 to 2 mg/L. This is an easily implemented adjustment and dramatically improves the chlorine reliability (<0.9 at only 15% of the nodes), even for the most extreme future water conservation scenario. However, this reliability comes at the cost of higher yet compliant THM concentrations for the low demand scenarios, revealing the challenges of balancing competing water quality goals. With a goal of maintaining a reference level of THMs at ≤80 ug/L, the THM reliability index is ≥0.9 at almost all nodes even under the most extreme conservation scenario. The evaluation of self-cleaning potential velocities shows that sufficient velocities can only be reached at daily maximum flow in 5% of smaller diameter piping even in the reference scenario.

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