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The Opportunities and Economics of Direct Potable Reuse

Project: 14-08
Year Released: 2014
Type: White Paper

Program: Principal
Total Investment: $25,000

Principal Investigators: Bob Raucher, Ph.D., Stratus Consulting and George Tchobanoglous, University of California, Davis


Water shortages, the limitations of current water supplies, the impacts of climate change, and new legal definitions of water and water rights are motivating water agencies to expand and secure their water portfolios. Included in the mix of water supply sources being considered are indirect potable reuse (IPR) and direct potable reuse (DPR). To assist water agencies, the WateReuse Association, the WateReuse Research Foundation, and WateReuse California have provided leadership by sponsoring a combination of research, advocacy, and education and outreach in IPR and DPR. However, a number of questions have arisen that demand answers. For example, how much will DPR cost versus other sources of water? What is the carbon footprint of DPR, and how much new water could be made available through DPR in California? To answer these questions, the WateReuse Research Foundation commissioned the preparation of this White Paper.

Goals and Objectives

The project evaluates the cost of direct potable reuse as well as the amount of wastewater available for direct and indirect reuse.

Research Approach

  • DPR costs were evaluated for the for complete advanced treatment process (CAT) of MF, RO, UV/AOP, Cl2 Disinfection)
  • The sources of information used to assess the cost of the CAT process were (1) the costs and operational expenses of the original Groundwater Replenishment System (GWRS) in Orange County, CA put into operation in 2008 and (2) the bid prices and estimated operational expenses for the expansion of the GWRS to be put into operation in 2015.
  • The estimated costs of the CAT facilities of other proposed DPR and/or IPR alternatives were reviewed for consistency.
  • The amount of water that could be made available through DPR was addressed by estimating the amount of treated wastewater that will be discharged to surface waters or the ocean and then estimating the amount that could potentially be available for recycling, including DPR and IPR.

Findings and Conclusions

In California, there is a considerable quantity of highly treated wastewater that is discharged to the ocean or inland waterways. It is estimated that more than 2,300 Mgal/d (2.6 MAF/y) may be available in California for new water recycling projects in 2020, potentially yieling more than 1,000 Mgal/d (1.1 MAF/y) of potable supplies. To place this into context, this is sufficient potable water to supply all municipal needs (including commercial and industrial uses) for more than 8 million Californians. This study also shows that potable reuse compares favorably with other new water supply alternatives in terms of cost, energy requirements, and other environmental considerations. Specific costs of IPR and DPR are highly site specific but adding DPR to the water supply mix for California will enable many communities to tap into potable reuse where IPR is not feasible and save many communities on cost and energy usage.

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