Distribution System Contamination Research Articles

Prediction of Water Distribution System Contamination Based on Wildfire Burn Severity in Wildland Urban Interface Communities

The devastation to infrastructure in wildland urban interface (WUI) communities caused by wildfires has brought attention to the dramatic and unforeseen impacts of high fuel load density within the...

Limitations of E. coli Monitoring for Confirmation of Contamination in Distribution Systems due to Intrusion under Low Pressure Conditions in the Presence of Disinfectants

AbstractLow/negative pressure events that increase the risk of contaminant intrusion may take place in distribution systems and may become more common in ageing infrastructure. Guidance on whether ...

A framework for real-time disinfection plan assembling for a contamination event in water distribution systems

Water distribution system contamination events caused by intentional, negligent, or accidental intrusion of biological, chemical, or radioactive contaminants have significant impacts on the health of the populations that it services. Therefore, it is important to have an effective plan that can be readily implemented to minimize the impact of these contamination events. However, limited research has been focused on strategic planning of the decontamination process of the contaminated infrastructure. This paper proposed a framework for assembling a disinfection plan in real-time by (1) partitioning a WDS into a number of district metered areas (DMAs), (2) generating a solution region for each of the DMAs, and (3) assemble an effective decontamination plan using solution region generated. This framework has been applied to three contamination events. The results show that, when planning for the decontamination stage of a contamination event, the use of the proposed framework can (1) significantly reduce the response time, (2) improve the quality of the decontamination plan, and (3) provide a model for optimizing the resource allocation.

Analysis of building plumbing system flushing practices and communications.

Drinking water distribution system contamination incidents can prompt public agencies and drinking water utilities to issue do-not-drink and do-not-use advisories. After the contaminant is cleared from distribution mains, consumers are often directed to flush their plumbing. However, little validated guidance and few evaluated communications strategies are available on using flushing to decontaminate building water systems. Additionally, limited data support the effectiveness of current practices and recommendations. In this study, expert elicitation was used to assess existing flushing guidance and develop validated flushing guidance and communications for single-family residences. The resulting guidance recommends progressively opening all cold-water taps from the closest to point of entry to the furthest and allowing the water to run for at least 20 minutes. Hot-water taps should be opened progressively and run for at least 75 minutes. The guidance language and format conformed to grade-level and readability scores within recommended health communication ranges. The readability of eight other flushing guidance documents was also evaluated for contamination incidents from 2008-2015. Seven were written at a 10th-12th grade level, above the 6th-7th grade level recommended for health communications.

A mixed-method examination of risk factors in the truck-to-cistern drinking water system on the Beardy’s and Okemasis First Nation Reserve, Saskatchewan

The provision of safe drinking water is a key driver of public health and a pressing health issue facing First Nations communities in Canada. Contaminated water is a perennial issue for reserve communities across the country despite numerous government investments. Many First Nations communities rely heavily on cistern use for their drinking water supply; however, bacterial contamination within these systems is frequent and a common reason for household boil water advisories. The sources of contamination during the process of hauling water to cisterns in First Nations communities have received limited attention in academic research. The purpose of this research is to identify the risks to water quality through the truck-to-cistern water system. In partnership with a Saskatchewan First Nations community, drinking water quality was monitored in the treatment plant, in delivery trucks and at 142 household cisterns and taps from July to October, 2014. Risks to water supply were identified through monthly water sampling and laboratory analysis, key informant interviews, and observation. Coliform contamination in trucks, cisterns and taps was most common during August. Total coliforms were more likely to be found in cisterns compared to household taps and samples from trucks. Chlorine residuals were lower in household tap samples than in cisterns for August and September. Together with the community, investigators identified contamination and bacteriological growth in cisterns and household distribution systems, and variable levels of total chlorine concentrations depending on month and site of sampling. Recommendations are provided for advancing guidelines on management of truck-to-cistern drinking water supply chains in First Nations.

Robust Sampling and Lab Prep Bolster Incident Response

Early detection of distribution system contamination, combined with effective response actions, can mitigate a community's public health and economic consequences. Sampling and analysis is one of the earliest utility‐led response actions performed when contamination is suspected ‐ and is continued if contamination is confirmed.

Complex Adaptive Systems Framework to Simulate the Performance of Hydrant Flushing Rules and Broadcasts during a Water Distribution System Contamination Event

AbstractIn the event that a contaminant is introduced to a water distribution system, utility managers must respond quickly to protect public health. Mitigation strategies specify response actions,...

Ensure Cross‐Connection Control and Backflow Prevention with a Multipoint Approach

Cross‐connections are significant risks to water quality and public health. Utilities can help prevent distribution system contamination through proactive cross‐connection control measures.

A dynamic simulation–optimization model for adaptive management of urban water distribution system contamination threats

Urban water distribution systems hold a critical and strategic position in preserving public health and industrial growth. Despite the ubiquity of these urban systems, aging infrastructure, and increased risk of terrorism, decision support models for a timely and adaptive contamination emergency response still remain at an undeveloped stage. Emergency response is characterized as a progressive, interactive, and adaptive process that involves parallel activities of processing streaming information and executing response actions. This study develops a dynamic decision support model that adaptively simulates the time-varying emergency environment and tracks changing best health protection response measures at every stage of an emergency in real-time. Feedback mechanisms between the contaminated network, emergency managers, and consumers are incorporated in a dynamic simulation model to capture time-varying characteristics of an emergency environment. An evolutionary-computation-based dynamic optimization model is developed to adaptively identify time-dependant optimal health protection measures during an emergency. This dynamic simulation–optimization model treats perceived contaminant source attributes as time-varying parameters to account for perceived contamination source updates as more data stream in over time. Performance of the developed dynamic decision support model is analyzed and demonstrated using a mid-size virtual city that resembles the dynamics and complexity of real-world urban systems. This adaptive emergency response optimization model is intended to be a major component of an all-inclusive cyberinfrastructure for efficient contamination threat management, which is currently under development.

Errata

This errata makes several corrections to the following articles in the March 2014 issue: “Testing an Innovative Evaporative Suppressant for Reducing Losses From Lakes” by Kent Sovocool et al; “Transform the Lowly Rebate Into the Upfront Cash of a Coupon Bonanza!” by Melanie K. Goetz; “DNA‐based Microbial Analysis Detects and Locates Potential Contamination in Distribution Systems” by Trevor Ghylin; and “A Florida Case Study on the Protection of Source Water” by William S. Bilenky and Paria Shirzadi.

DNA‐based microbial analysis detects and locates potential contamination in distribution systems

DNA technology can fill in the gaps left by other microbial testing methods.

Sociotechnical risk assessment for water distribution system contamination threats

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.

Probabilistic Analysis and Optimization to Characterize Critical Water Distribution System Contamination Scenarios

AbstractCharacterization of critical water distribution system (WDS) contamination scenarios—defined by a set of attributes, a probability of occurrence, and a specific level of consequences—is a prerequisite for preparation of reliable and cost-effective mitigation, preparedness, and emergency response plans. This study develops Monte Carlo and risk-based optimization schemes to evaluate contamination risk of WDSs for generation of this important class of scenarios, which are representative of the most vulnerable aspects of the system. Defining attributes of contamination scenarios are identified as contaminant type and amount, contamination location, start time, duration, and time of year scenario occurs. Well-documented waterborne outbreaks reported in developed nations are analyzed to empirically estimate statistical characteristics of defining attributes in accidental events. Monte Carlo simulation is conducted to determine the probability distribution of public-health consequences, aggregate conditi...

The Safe Drinking Water Act: Current and Future

Rather than stretching to try to regulate components of marginal concern, fixing and maintaining infrastructure and reducing leaks, backflow, cross connections, and contamination in distribution systems should be the priorities of the drinking water delivery community.

Protecting Public Health and the Distribution System—Optimizing Consequence Management Procedures in a CWS

In the April JOURNAL's Security and Preparedness column, “Developing SOPs for the Investigation of Distribution System Contamination,” Allgeier and co‐authors discussed the importance of having established procedures that guide the day‐to‐day monitoring of a contamination warning system (CWS) and the investigation that follows an alert. The article in this month's Security and Preparedness column highlights examples and lessons learned from the CWS pilot program in Cincinnati, Ohio, which is primarily operated by the Greater Cincinnati Water Works. The information is presented as a series of questions and answers that arise during a fictional contamination incident.

Developing SOPs for the Investigation of Distribution System Contamination

This article uses examples and lessons learned from the Greater Cincinnati Water Works (GCWW) contamination warning system (CWS) to show the importance of standard operating procedures (SOPs) for investigating indicators of possible distribution system contamination. This information is presented in the context of a series of questions addressed during development of procedures for the GCWW CWS.

Agent‐Based Modeling to Simulate Contamination Events and Evaluate Threat Management Strategies in Water Distribution Systems

In the event of contamination of a water distribution system, decisions must be made to mitigate the impact of the contamination and to protect public health. Making threat management decisions while a contaminant spreads through the network is a dynamic and interactive process. Response actions taken by the utility managers and water consumption choices made by the consumers will affect the hydraulics, and thus the spread of the contaminant plume, in the network. A modeling framework that allows the simulation of a contamination event under the effects of actions taken by utility managers and consumers will be a useful tool for the analysis of alternative threat mitigation and management strategies. This article presents a multiagent modeling framework that combines agent-based, mechanistic, and dynamic methods. Agents select actions based on a set of rules that represent an individual's autonomy, goal-based desires, and reaction to the environment and the actions of other agents. Consumer behaviors including ingestion, mobility, reduction of water demands, and word-of-mouth communication are simulated. Management strategies are evaluated, including opening hydrants to flush the contaminant and broadcasts. As actions taken by consumer agents and utility operators affect demands and flows in the system, the mechanistic model is updated. Management strategies are evaluated based on the exposure of the population to the contaminant. The framework is designed to consider the typical issues involved in water distribution threat management and provides valuable analysis of threat containment strategies for water distribution system contamination events.

Planning Unidirectional Flushing Operations as a Response to Drinking Water Distribution System Contamination

This paper addresses the issue of contaminated water evacuation as part of the response process in cases of intentional or accidental contamination of drinking water distribution systems (DWDSs). Following a previous study which addressed contaminant isolation, an original flushing procedure (FP) is introduced. Through a heuristic set of rules, the FP defines unidirectional flushing (UDF) strategies in a safe, structured, and efficient manner. In addition to the rather theoretical considerations related to hydraulics modeling, the FP also takes into account the operational issues of UDF implementation. Compared to other similar studies, the latter aspect establishes the main contribution of this paper. The FP has been applied to two real-world networks and application of the heuristic rules is demonstrated with the aid of a detailed example. General results suggest possible improvements to existing network configurations and to the design of projected networks to better support contamination response plan...

Drinking water quality in household supply infrastructure—A survey of the current situation in Germany

As a result of the amendment to the German Drinking Water Ordinance in 2001, local public health authorities are obliged to monitor the water supply in installations providing water for public use (Section 18 German Drinking Water Ordinance). With a systematic and nationwide survey of locally available data relating to hygienic drinking water quality and the existing drinking water infrastructure in buildings, the extent of microbial contamination of in-building distribution systems in Germany is intended to be assessed. To gain an overview of the microbial contamination of drinking water in public buildings all 419 local public health authorities in Germany were contacted in 2007. In a detailed study with a representative cooperation level of 5% of these local public health authorities, the available data relating to microbiological, chemical, physical and technical parameters gained from in-building distribution systems were collected. Drinking water parameters were combined with regard to the total number of analyses and the absolute number as well as the percentage of limit compliance failures (n=108,288). Limits exceeded were classified as the failure to comply with the German Drinking Water Ordinance, DVGW technical regulations and Federal Environment Agency recommended limits. The highest rates of samples exceeding these limits were found for the parameter Legionella sp. which contaminated 12.8% of all samples (n=22,786; limit: 100 CFU/100ml), followed by heterotrophic plate count at 36 degrees C (3.5%, n=10,928; limit: 100 CFU/1 ml) and Pseudomonas sp. (2.9%, n=3468; limit: 0 CFU/100ml). Legionella sp. and Pseudomonas sp. pose a direct health risk to immunosuppressed users. Additionally, for some chemical parameters, such as nickel, iron and lead, a potential risk for the health of consumers was detected. Further data analysis may reveal whether this contamination is related to stagnation where there is only sporadic use or whether other factors are involved in the process of microbial growth in installation systems.

Occurrence of Contaminant Accumulation in Lead Pipe Scales from Domestic Drinking-Water Distribution Systems

Previously, contaminants, such as AI, As, and Ra, have been shown to accumulate in drinking-water distribution system solids. Accumulated contaminants could be periodically released back into the water supply causing elevated levels at consumers taps, going undetected by most current regulatory monitoring practices and consequently constituting a hidden risk. The objective of this study was to determine the occurrence of over 40 major scale constituents, regulated metals, and other potential metallic inorganic contaminants in drinking-water distribution system Pb (lead) or Pb-lined service lines. The primary method of analysis was inductively coupled plasma-atomic emission spectroscopy, following complete decomposition of scale material. Contaminants and scale constituents were categorized by their average concentrations, and many metals of potential health concern were found to occur at levels sufficient to result in elevated levels at the consumer's taps if they were to be mobilized. The data indicate distinctly nonconservative behavior for many inorganic contaminants in drinking-water distribution systems. This finding suggests an imminent need for further research into the transport and fate of contaminants throughout drinking-water distribution system pipes, as well as a re-evaluation of monitoring protocols in order to more accurately determine the scope and levels of potential consumer exposure.