Keywords: premeditated destructive events, fuzzy logic, fuzzy set theory, expert opinion, end-users of treated water, public utilities, construction, design.

This paper describes a method for assessing consequences to end-users of a water treatment system failure resulting from Premeditated Destructive Events (PDEs). In order to realize the complex challenge of protecting municipal water treatment facilities from PDEs, it is essential to visualize these facilities as composed of a number of components, each with a specialized function and often in different spatial locations, often located miles, even hundreds of miles apart. Because these components are not clustered in the same location each component should be considered separately when studying terrorist activities.

Most municipal water treatment systems can be represented by the following components: raw water storage in reservoirs, raw water intake where water is pumped into rotating screens to remove large objects such as sticks and leaves and then pumped on to post screening storage or directly to the beginning of the water treatment process. Suspended solids are removed through coagulation and sedimentation. Liquid alum is added to cause suspended particles to coagulate and settle to the bottom of the basin taking most of the contaminants with it to form sludge. The sludge is continuously pumped to storage lagoons. In regions where the water is hard, softening the water with lime and soda ash and corresponding pH adjustments by adding carbon dioxide improve the way water performs. Filtration through layered filters of gravel, sand and very fine carbon removes particles not removed by coagulation and sedimentation. Chemical water purification usually with chlorine disinfects the water. Finally, water finishing including fluoridation and corrosion control completes the treatment process. The distribution system includes post-treatment storage in clear wells and water towers to maintain pressure.

Experts rank physical attacks as the PDE of primary concern to water treatment facilities, followed by biological and chemical attacks. Biological attacks are of concern in the post treatment distribution system. System-wide chemical attacks are unlikely due to the dilution factor; however localized chemical attacks are possible. Because most water treatment facilities have manual backup controls for all electronically controlled valves and equipment and computer systems are primarily interconnected through local area hardwired networks rather than using external internet or other electronic connections, cyber attacks although possible are not considered likely. Nuclear bombings are considered unlikely; however, nuclear contamination is a possible consideration. Hence, the first application of this method is to the consequences to end-users of a disruption in the water supply from a physical PDE.

Using fuzzy logic and fuzzy set theory, the method captures expert opinion from end-users, professionals representing end-users and water treatment personnel. By identifying and evaluating the consequences of a water outage to various end-user groups as a result of PDEs, it provides a basis for investigating the relative vulnerability of the various components of municipal water treatment systems.

The authors believe that this method has broad economic, social, and scientific impact upon many aspects of our lives of people through the world. The vast majority of people in developed countries receive drinking water from large municipal systems. A terrorist attack on any one of these systems could potentially close down the community it serves sending economic repercussions that extend far beyond the community served by the municipal water treatment facility.

The method described in this paper captures expertise within the community in such a way that it can be used for assessing the consequences of a physical PDE on a community of end-users of treated water. It enables communities to evaluate and understand the consequences of an outage of treated water to their community taking into account the uniqueness of their own community in terms of the mix of residential, commercial, industrial and government end-users of water as well as special considerations to the geography and water treatment facilities of the community. The results are used as input into assessing the vulnerabilities to PDEs of a municipal water treatment system.

A limitation of this method is the use of a binary model for water outage. The water is considered either on or off. The authors recommend that the method be extended to include intermediate values of a water outage such as loss of water pressure, rationing of water supply, and post-treatment of water by end-users such as a "boil-water" alert.

The method as it is formulated is applicable to public utilities other than water. The authors recommend that the method be extended to evaluating the consequences to end-users of an outage of other utilities, such as electric power, natural gas, and telephone communications.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £82 +P&P)