Application of HACCP to Re-Evaluate Secondary Disinfection

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Secondary disinfection of drinking water is intended to protect against intrusion in distribution systems, suppress biofilm and opportunistic pathogens, and serve as a sentinel of system failure. Despite these commonly-cited objectives, there is no evidence-based regulation or guideline that defines the type or concentration of secondary disinfectant required to achieve them. Instead, secondary disinfection practices have remained largely unchanged for 100 years, with little attempt to determine whether, and to what extent, they are doing their job. This is becoming increasingly unacceptable, as evidence suggests that the majority of outbreaks of disease from drinking water in developed countries may be attributable to failures in the distribution system, and awareness grows about new classes of disinfection by-products, and the presence of opportunistic pathogens in premise plumbing. The proposed research will re-evaluate secondary disinfection needs through a hazard analysis and critical control point (HACCP) approach, coupled with quantitative microbial risk assessment (QMRA). The work will identify research gaps that inhibit the completion of the HACCP/QMRA models, and identify priority areas for further research to be undertaken by the applicant through third party funding, or by others. The risk assessment work will be supplemented by a field-, pilot-, and laboratory-scale case study of the ability of a proposed new secondary disinfectant, stabilized hydrogen peroxide, to meet the needs identified by the HACCP analysis. The funding will support the training of 14 highly qualified personnel, who will learn skills in risk analysis as well as applied skills in water treatment operation and the performance of a variety of microbiological and chemical analyses. This are high value skills that are directly transferrable to the environmental engineering industry.The proposed work will not transform secondary disinfection practices on its own: the resources and scope are too limited. The intent is to use HACCP and QMRA tools to create a rational framework to allow secondary disinfection to be critically assessed using quantitative performance metrics for the first time, and to discover and identify priority areas for further investigation. This will stimulate a new research direction in the drinking water community, which will ultimately lead to more rational, health-based secondary disinfection practices and regulations.