Home\Educate\Water Reuse 101\Research Projects\Year\2014\Risk Reduction for Direct Potable Reuse

Risk Reduction for Direct Potable Reuse

Project: 11-10
Type: Decision Making Tool
Year Released: 2014

Program: Principal
Funding Partners: City of San Diego, City of Escondido, City of Ventura
Total Investment: $171,381.10 (Cash: $104,407, In-Kind: $66,974.10)

Principal Investigators: Andrew Salveson, Carollo Engineers, Inc., and Erin Mackey, Carollo Engineers, Inc.


Across the country, successful indirect potable reuse projects are now creating more than 100 million gallons per day of potable water. Nationally to ensure water supply reliability at a reasonable cost, there is now a movement towards direct potable reuse. In May 2013, the first direct potable reuse (DPR) facility began operation in the United States, with more soon to follow. The underlying principles documented within this project are intended to provide a framework for the safe implementation of DPR.

Goals and Objectives

The project identifies how risk reduction and response concepts developed in other industries (structural/bridge, aviation/NASA) can be adapted and applied to DPR. The results provide new perspectives on how to consider risk management and an understanding of what engineering practices could be incorporated into our approach to the design, control, operation, and maintenance of advanced treatment systems.

Research Approach

The research approach was to evaluate the treatment performance of current IPR practices and considers what additional treatment and monitoring and operational issues may be necessary to safely implement DPR. Further, this study investigated other industries’ approaches to mitigating risk and combined this information into a risk reduction framework for evaluating the pros, cons, and costs of the identified DPR approach alternatives.

Findings and Conclusions

Successful implementation of DPR depends upon many factors, including an understanding of acute versus chronic risk, and use of accurate online and rapid response monitoring.

  • Acute versus Chronic Risk: In evaluating risk and developing a risk management approach, the top priority should be controlling acute risks (exposure to pathogens). Exposure to chronic risks is also important and must be an integral part of the DPR design and operational process; however, chronic risks represent a lower relative priority.
  • Online Monitoring and Rapid Response Monitoring: In the absence of an environmental buffer, treatment processes need accurate, robust real-time online monitoring of effluent quality. This monitoring ideally ensures process performance and alarms when process effluent quality changes. These improved monitoring techniques should be sensitive enough to pick up small changes and trends in treatment performance that could have a significant impact on the safety of the finished water. The monitoring techniques would focus on both microbes and trace pollutants.

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