Identifying critical operational control points and strategies to minimize microbial risk during drinking water treatment

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Protozoan pathogens remain a significant public health threat associated with the provision of safe drinking water. Climate change is expected to exacerbate these risks due to increased frequency and intensity of extreme weather events. Most drinking water utilities reliant on surface water in North America utilize chemically-assisted filtration (CAF) as a key treatment process that is a required barrier to protozoan passage into treated drinking water supplies. Traditional monitoring strategies for treated water are ineffective at ensuring protozoan removal because 1) methods for the enumeration of protozoa are inadequate and 2) reliable surrogates for protozoan removal by CAF are not available. To protect public health from waterborne disease, traditional regulatory approaches have required specific equipment that is "well operated." Recently, the World Health Organization Guidelines for Drinking Water Quality (GDWQ) have recommended Water Safety Plans (WSPs) as a notably different, better, system-specific approach for managing pathogen risk in drinking water. Here, critical control points (CCPs) represent a point, step, or procedure at which control can be applied and, as a result, a water safety hazard can be prevented, eliminated, or reduced to an acceptable level. The development of a CCP-based approach for ensuring protozoan removal by CAF is proposed herein. The research includes the 1) integration of quantitative microbial risk assessment (QMRA) with the CCP-approach for minimizing protozoan passage through CAF and 2) development of an image analysis tool for rapid protozoan identification and enumeration. This work will help to advance protozoan pathogen risk management by CAF during drinking water treatment. It will contribute new knowledge, generate technological innovation, and train highly qualified personnel who can effectively apply emerging scientific tools for risk assessment to develop improved drinking water treatment strategies, technologies, and policies. The long-term benefits of this research include helping to reduce the societal costs of water-related illnesses and enabling innovative, water utility-specific WSPs and adaptation strategies in response to land disturbances and changing climate.******