Tools to Assess and Understand the Relative Risks of Indirect Potable Reuse and Aquifer Storage and Recovery Projects
Year Released: 2013
Type: Decision Making Tool
Program: Tailored Collaboration
Funding Partners: Bureau of Reclamation, Inland Empire Utilities Agencies, Water Replenishment District of Southern California, West Basin Municipal Water District, City of Phoenix Water Services, Los Angeles County Sanitation District, Los Angeles Department of Water and Power, Orange County Water District
Total Investment: $522,787.70 (Cash: $477,911.76, In-Kind: $74,875.94)
Principal Investigators: Margaret H. Nellor, P.E., Nellor Environmental Associates, Inc., and Jeffrey Soller, Soller Environmental, LLC
An increasing number of municipalities are considering implementing projects to augment potable water supplies with reclaimed water. Indirect potable reuse (IPR) projects face many uncertainties with assessing the potential human health risks of exposure to reclaimed water such as limited data, insufficient or costly evaluation tools, and the advent of new pollutants of concern. Thus it is difficult to directly answer questions about the potential health significance of IPR projects or the level of treatment required for specific projects.
Goals and Objectives
The project develops information and tools to evaluate the use of reclaimed water for indirect potable in terms of: 1) quantitative relative risk assessments; 2) screening level exposure concentrations and risk metrics for a 43 constituents of emerging concern; 3) new pharmaceuticals that might be produced in large quantities over the next 5 to 20 years, their ability to persist after treatment, and an expert elicitation tool to captures professional judgment.
In this project a quantitative relative risk assessment (QRRA) for two operating groundwater recharge projects was conducted based on the presence or absence of regulated chemicals. Screening drinking water equivalent levels were developed for 43 chemicals, including pharmaceuticals and endocrine disrupting compounds. Risk metrics were developed to put the health risk information into perspective. Following this, future pharmaceuticals were predicted as likely to be used in high volume over the next 5 to 20 years, and their ability to persist after tertiary wastewater treatment, soil aquifer treatment, or reverse osmosis treatment. A unique expert elicitation tool was developed that captures professional judgment about uncertain risks, but does not entail the costs of more traditional in-person approaches for seeking expert opinions.
Findings and Conclusions
This was one part of a three part study.Task 3 has developed information to predict future chemicals of concern by identifying new pharmaceuticals that might be produced in large quantities over the next 5 to 20 years; evaluating their ability to persist after tertiary wastewater treatment, soil aquifer treatment (SAT), or reverse osmosis treatment; and developing an expert elicitation tool that captures professional judgment about uncertain risks. The expert elicitation tool is unique in that it does not entail incurring the costs of more-traditional in-person approaches for seeking expert opinions.
The work presented here has numerous practical applications that can be applied to other indirect potable reuse projects to gauge their relative safety with respect to human health. These tools can be used to (a) assess project safety for regulated compounds and current and future chemicals of concern; (b) provide a basis for focusing source control efforts; © develop a better understanding of the utility of conventional treatment, SAT, and advanced treatment in reducing risk; (d) assist with prioritizing and updating monitoring programs; and (e) provide information for public outreach.
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