PLANNED POTABLE REUSE: URBAN WATER INSTITUTE’S SPRING WATER CONFERENCE THE LAST FRONTIER URBAN WATER INSTITUTE’S SPRING WATER CONFERENCE Palm Springs, California February 8, 2017 George Tchobanoglous Professor Emeritus Department of Civil and Environmental Engineering University of California, Davis

Paradigm shift in view of water What is potable reuse? Discussion Topics Paradigm shift in view of water What is potable reuse? Technologies for potable reuse Cost and energy implications? Where does potable reuse fit in the water portfolio Driving forces for potable reuse Sources of information Closing thoughts

A PARADIGM SHIFT IN VIEW OF WATER Wastewater is a renewable recoverable source of potable water, resources, and energy.

What Is Potable Reuse? Current definitions for the different types of potable reuse de facto indirect potable reuse (df-IPR) Indirect potable reuse (IPR) Direct potable reuse (DPR) Proposed definitions for potable reuse

OVERVIEW: DE FACTO INDIRECT POTABLE REUSE The downstream use of surface water as a source of drinking water that is subject to upstream wastewater discharges. Courtesy City of San Diego

“Clean Water and How to Get It” Allen Hazen (1914) “Clean Water and How to Get It” “Looking at the whole matter as one great engineering problem, it is clear and unmistakably better to purify the water supplies taken from rivers than to purify the sewage before it is discharged into them. It is very much cheaper to do it this way. The volume to be handled is less and the per million gallons the cost of purifying water is much less than the cost of purifying sewage.”

OVERVIEW: INDIRECT POTABLE REUSE Typical injection well - OCWD San Vicente reservoir, San Diego, CA

OVERVIEW: DIRECT POTABLE REUSE DPR with Advanced Treated Water (ATW) DPR with Finished Water

Proposed definitions for Potable reuse (After West Basin) 1. Groundwater Augmentation  (With six-month or greater retention time in an environmental buffer) 2. Surface Water Augmentation  (With six-month or greater retention time in an environmental buffer with an initial dilution of 100 to 1) 3. Raw Water Augmentation (Commingling with other raw sources followed by treatment in a water treatment facility) 4. Treated Water Augmentation (Finished water delivered directly into a treated water supply distribution system)

PICTORIAL VIEW OF POTABLE REUSE

Technologies for the Potable Reuse TECHNOLOGY IS NOT A LIMITING CONSTRAINT!!

EXAMPLE OF TREATMENT PROCESSES for Potable Reuse: Orange County Water District AWTF Adapted from OCWD

Microfiltration, Cartridge Filters, Reverse Osmosis, and Advanced Oxidation (UV) Technologies at OCWD Microfiltration Cartridge Filters Reverse Osmosis Advanced Oxidation

Decarbonator (CO2 Stripping) DECARONATION AND LIME SATURATION AT OCWD Decarbonator (CO2 Stripping) Lime Saturator (pH adjustment)

What Does DPR Cost? Note: $/103 gal x 325.89 = $/AF Data from original OCWD AWTF

DPR ENERGY USAGE Note: kWh/103 gal x 325.89 = kWh/AF Data from original OCWD AWTF

where does potable reuse fit IN The water Portfolio? WATER SOURCES Local surface water Local groundwater (shallow and deep) Imported water Potable reuse (DPR and IPR, potential 20 to 40%) Desalination (brackish and sea water) Stormwater (?) OTHER MEASURES Centralized non-potable reuse (e.g., purple pipe) Decentralized non-potable reuse (e.g.,greywater) Conservation and curtailments

DRIVING FORCES FOR IPR AND DPR The value of water will increase significantly in the future (and dramatically in some locations). Population growth and global warming will lead to severe water shortages in many locations. De facto indirect potable reuse is largely unregulated (e.g., secondary effluent, ag runoff, urban stormwater, highway runoff). Infrastructure requirements limit most urban reuse opportunities (e.g., dual distribution systems). Existing and new technologies can meet the water quality challenge to protect public health. Stringent environmental regulations.

useful INFORMATION SOURCES FOR DPR 2015 2011 2014 2015 October 2016 POTABLE REUSE RESEARCH COMPILATION: SYNTHESIS OF FINDINGS WE&RF PROJECT NO. 15-01 December 2016

TAKE AWAY THOUGHTS Ultimately, potable reuse is inevitable and will represent an essential element of a sustainable water future Must think of wastewater differently Must recognize technology is not an issue Must recognize public is supportive Must recognize that bold new planning is needed-now!!

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