BOX 11-1
Summary of Research Priorities

These research areas hold significant potential to advance the safe, reliable, and cost-effective reuse of municipal wastewater where traditional sources are inadequate. They are not prioritized here.

Health, Social, and Environmental Issues

1. Quantify the extent of de facto (or unplanned) potable reuse in the United States.

2. Address critical gaps in the understanding of health impacts of human exposure to constituents in reclaimed water.

3. Enhance methods for assessing the human health effects of chemical mixtures and unknowns.

4. Strengthen waterborne disease surveillance, investigation methods, governmental response infrastructure, and epidemiological research tools and capacity.

5. Assess the potential impacts of environmental applications of reclaimed water in sensitive ecological communities.

6. Quantify the nonmonetized costs and benefits of potable and nonpotable water reuse compared with other water supply sources to enhance water management decision making.

7. Examine the public acceptability of engineered multiple barriers compared with environmental buffers for potable reuse.

Treatment Efficiency and Quality Assurance

8. Develop a better understanding of contaminant attenuation in environmental buffers.

9. Develop a better understanding of the formation of hazardous transformation products during water treatment for reuse and ways to minimize or remove them.

10. Develop a better understanding of pathogen removal efficiencies and the variability of performance in various unit processes and multibarrier treatment and develop ways to optimize these processes.

11. Quantify the relationships between polymerase chain reaction (PCR) detections and viable organisms in samples at intermediate and final stages.

12. Develop improved techniques and data to consider hazardous events or system failures in risk assessment of water reuse.

13. Identify better indicators and surrogates that can be used to monitor process performance in reuse scenarios and develop online real-time or near real-time analytical monitoring techniques for their measurement.

14. Analyze the need for new reuse approaches and technology in future water management.

tem permit holders, and hydrological models developed to study watersheds with historical concerns about the impact of effluent discharges on water quality. These efforts could be updated periodically (e.g., every 5 to 10 years) to provide decision makers with an understanding of the role of de facto reuse in the nation’s potable water supply. Furthermore, an improved understanding of de facto potable reuse could spur the development and/or application of contaminant prediction tools or lead to enhanced monitoring programs that could increase public health protection.

2. Address critical gaps in the understanding of health impacts of human exposure to constituents in reclaimed water.

Potential health impacts resulting from long-term, low-level exposure to chemicals and mixtures of chemicals present in wastewater effluent have yet to be fully elucidated. It would be expensive and time-consuming to conduct batteries of in vitro and in vivo toxicity studies on all of the different chemicals in reclaimed water. However, a carefully planned research effort would be useful to inform future decisions about potable water reuse. In particular, there is a need to fill in data gaps in existing toxicological databases with respect to contaminants that are known to occur in wastewater and persist in the environment and are refractory in water reclamation and water treatment processes. The risk exemplar (Chapter 7) highlights several of these chemicals, including nitrosamines, disinfection byproducts, hormones, certain pharmaceuticals, antimicrobials, flame retardants, and perfluorochemicals. As noted in Chapter 6, there is also a need to assess the importance of indirect pathways of exposure to constituents in reclaimed water, such as bioaccumulation of trace organic chemicals in food crops.

3. Enhance methods for assessing the human health effects of chemical mixtures and unknowns.

Concerns about the health effects of unknown chemicals and contaminant mixtures remain a major challenge in public and political acceptance of water reuse. Additional research is needed to further develop in vivo and in vitro bioassay methods that can be used to rapidly and selectively screen the product water from

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