Water Online

JAN 2016

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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New research reveals the value and economics of direct potable reuse (DPR), as well as how to get started. By Justin Mattingly T he prolonged and ongoing drought in California and other regions in the Southwest has made water supplies increasingly scarce, highlighting the need to secure new and sustainable sources of potable water. One such option is to more effectively utilize existing wastewater resources through water reuse, and direct potable reuse (DPR) in particular, to supplement existing water supplies. Through a joint effort between WateReuse, the American Water Works Association (AWWA), and the Water Environment Federation (WEF), the report "Framework for Direct Potable Reuse" was developed by an independent advisory panel administered by the National Water Research Institute (NWRI) to provide information about the value of DPR as a water supply option and what is needed to implement a DPR program. Communities can find numerous advantages — including enhanced water supply reliability, decreased energy usage, greater value from limited natural water supplies, and controlled increases to the cost of water — by considering DPR as part of their water supply portfolios. In California alone, there is great potential for the expansion of potable water reuse. A 2014 study from WateReuse estimated that by 2020, over 2,300 MGD in treated wastewater will be discharged to surface waters or the ocean. Of this amount, over 1,000 MGD could be used for either indirect potable reuse or DPR. This amount would meet the residential, commercial, and industrial water needs for eight million people, or more than 20 percent of the projected population of California in 2020. There is also significant potential in other regions of the country, including Big Spring, TX, which has a DPR facility currently in operation. The framework document is aimed at making this potential a reality throughout the country by paving the way for a sustainable source of drinking water that is protective of public health and resilient in the face of drought and climate change. What Is Direct Potable Reuse? Although not often acknowledged, communities throughout the U.S. currently engage in potable water reuse, where downstream surface waters used as a source of drinking water are subject to upstream wastewater discharges. This is commonly referred to as unplanned or de facto potable reuse. Conversely, planned potable reuse can take the form either of indirect potable reuse, where an environmental buffer such as an aquifer or reservoir is present, or direct potable reuse, where no such environmental buffer is present. Direct potable reuse can be implemented in two ways: 1. Advanced treated water is introduced with or without the use of an engineered storage buffer (ESB) into the raw water supply immediately upstream of a drinking water treatment facility (DWTF). To date, permitted operational DPR facilities in the U.S. involve this form of DPR. 2. Finished water is directly introduced — with or without the use of an ESB — into a drinking water supply distribution system, either downstream of a DWTF or within the distribution system. Although a finished water DPR facility has been in operation at Windhoek, Namibia since 1967, the production of finished water is not the focus of the framework document. A number of communities throughout the country are currently considering implementing a DPR program to supplement their current potable water supply. To ensure that these projects protect public health, decision- makers need to understand the regulatory and operational components that must be part of a DPR program. While such a program will resemble existing drinking water and wastewater programs, there are some distinct differences and unique characteristics to DPR where further guidance is needed. The framework document sponsored by WateReuse, AWWA, and WEF details these important issues with information on the following topics: • Public health and regulatory aspects • Source control programs • Wastewater treatment 28 wateronline.com n Water Innovations Moving To A Future Of Potable Water Reuse

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