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    by Sheryl Hamlin

    The California State Water Resources Control Board Division of Drinking Water (DDW) hosted a two day webinar to report on the findings of the expert panel on the proposed criteria for Direct Potable Reuse (DPR) of wastewater. The expert panel members are:

    · Co-Chair: James Crook, PhD, PE, Engineering Consultant
    · Co-Chair: Adam Olivieri, DrPH, PE, EOA, Inc.
    · Richard Bull, PhD, Professor Emeritus, Washington State University
    · Jörg E. Drewes, PhD, Technical University of Munich
    · Charles Gerba, PhD, University of Arizona
    · Charles Haas, PhD, Drexel University
    · Amy Pruden, PhD, Virginia Tech
    · Joan Rose, PhD, Michigan State University
    · Shane Snyder, PhD, Nanyang Technological University and Univeristy of Arizona
    · Jacqueline E. Taylor, REHS, MPA, Director, Environmental Protection Branch, Los Angeles County Department of Public Health (Retired)
    · George Tchobanoglous, PhD, PE, University of California, Davis (Emeritus)
    · Michael P. Wehner, MPA, Orange County Water District (Retired)

    This panel represents substantial depth across research, public health and hands-on experience. It is also geographically diverse.

    California Framework for DPR (Direct Potable Reuse)

    The California DPR Framework has had two revisions: 2018 and 2019.

    California, Arizona, Texas, Florida, New Mexico and Colorado lead the way with regulations for DPR. The 2019 Water Reuse Symposium held in Flagstaff, Arizona summarized the various DPR initiatives. Read the summary here. It is important to understand that water is a multi-agency resource involving Public Health, energy companies, water companies, community Public Works, and legal teams at all levels.

    There are two type of water reuse: Indirect Potable Reuse (IPR) and Direct Potable Reuse (DPR). California allows IPR at this time, but not DPR. The following chart prepared by Corollo Engineering for the Flagstaff, Arizona meeting shows six state progress as of 2019.

    Legislative History in California

    The California work is based on AB 574 (2017), but actually started in 1991 with the California Water Recycling Act. Read about that history here.

    One of the requirements of AB 574 is a review by an expert panel of all criteria necessary to achieve DPR. This review must be completed by 2023. The meeting on August 24/25 reconstituted the expert panel, presented the review of the key criteria and solicited public comment. In 2016 the expert panel produced a lengthy report saying it was possible to codify criteria for potable reuse. Subsequently, definitions and criteria for DPR were released for comment.

    What Types of Water Reuse is Allowed Today in California?

    It is important to understand the following chart which was presented at the 8/24/2021 meeting. There are four scenarios for potable reuse. The top two show Indirect Potable Reuse (IPR) and the bottom two are Direct Potable Reuse (DPR). The top two are law in California, while the bottom two rows are not yet law and are the subject of the current Expert Panel review.

    Source: DPR Webinar August 24, 2021

    Groundwater recharge (first row) takes effluent from an Advanced Water Treatment Facility (AWTF) and injects this cleaned water below ground where nature will disperse it as needed. The second row Surface Water Augmentation sends effluent from an AWTF to a holding facility, reservoir, lake or established water reserve which can subsequently be processed by a Drinking Water Treatment Facility (DWTF). The holding facility creates an environmental buffer for the treated water.

    ”In 2018 the State Water Board adopted surface water augmentation regulations that establish minimum uniform water recycling criteria for he planned placement of recycled water into a surface water reservoir that is used as a source of domestic drinking water supply. “ Source: Science Direct

    Raw Water augmentation is a form of DPR (Direct Potable Reuse). “Raw water augmentation” means the planned placement of recycled water into a system of pipelines or aqueducts that deliver raw water to a drinking water treatment facility (DWTF) that provides water to a public water system, as defined in Section 116275 of the Health and Safety Code. Mar 4, 2019

    Treated Water Augmentation is another form of DPR (Direct Potable Reuse), wherein the treated effluent is sent directly to the water delivery system with no processing by a DWTF (Drinking Water Treatment Facility). It is often called “pipe-to-pipe”.

    Note that it is the environmental buffer that differentiates Indirect Potable Reuse (IPR) with Direct Potable Reuse (DPR). The Proposed Framework for DPR will develop criteria for DPR. Executive Summary

    Orange County

    “The GWRS is the world’s largest water purification system for indirect potable reuse. The system takes highly treated wastewater that would have previously been discharged into the Pacific Ocean and purifies it using a three-step advanced treatment process consisting of microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. The process produces high-quality water that meets or exceeds all state and federal drinking water standards.” Read MORE.

    San Diego

    A Surface Water Augmentation Project called “Pure Water” is a multi-phased project. See water flow here.

    Microbial Risk (DPR-1) and Pathogen Monitoring (DPR-2)

    A DPR facility will be permitted as a PWS (Public Water System) with the same standards as required by the federal Safe Drinking Water Act, but according to one speaker, California’s laws became more stringent in the 1980’s. This document defines the Risk Management approach to both Pathogen control and Chemical control starting at pdf page 18.

    Real-time monitoring will be required at multiple points. Production and delivery from the DPR facility must halt. SCADA systems must be reprogrammed for DPR. A halt implies that the facility into which the DPR water is delivered must have a backup source of water, a fact pointed out by several panel members.

    The researchers sampled five wastewater treatment facilities in California which contribute one third of California wastewater. The researchers modeled pathogen distribution and found similarities across 94% of the treatment plants and their models were able to describe pathogen distribution.

    One of the panelists asked a rhetorical question: if a wastewater treatment plant is already producing the highest quality effluent, then this DPR seems reactive rather than pro-act

    The research focused on entero, giardia and crypto virus, but their new on-line tool allows researchers to enter other measurable pathogens. The recommendation for CEC (Contaminants of emerging concern) includes this processing: 03/BAC (biologically activated carbon filter), RO (reverse osmosis) and AOP (advanced oxidation process). Dr. Pruden commented that the California DPR Framework is simply RO, according to some. The speaker agreed that this needed clarification.

    A reference to DPR-4 indicated other options in addition to RO:

    Reverse Osmosis

     

    Case Studies

    During the two days, reference was made to projects in Singapore, San Diego, Los Angeles, Monterey and Orange County, all in different stages. Orange County reported a 16 hour failure where acetone was delivered to the clean water reservoir. Los Angeles Hyperion had to dump millions of unprocessed water into the bay due to a failure.

    Audience Questions

    Prior to this period, all questions came from members of the expert panel. The last 30 minutes was open to the public for questions. The public asked about storage and handling prior to processing as a cost saving, illegal dumping of septic tanks, PFA removal and GAC (granular activated carbon), legal staff upgrades to all agencies, plant energy usage, redundant TOC analyzers. Sheryl Hamlin submitted these questions in advance and in the three minutes asked about pathogens from human composting, antibiotic resistance, prions and death rates versus infection rates.

    More DPR Information and Updates

    Please visit the CA DPR web site for updated information. The videos of the two day webinar should be posted here.

    For information on author click sherylhamlin dot com


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