by Sheryl Hamlin
On December 1, 2021, the second virtual meeting on potable reuse of wastewater hosted by the State of California was convened. Previously the State of California had chosen a panel of experts and a moderator to review the potable reuse criteria, per this statement of work:
The State Water Resources Control Board (State Water Board) and the National Water Research Institute (NWRI) have convened an expert review panel as required by Section 13561.2 of the Water Code to review the proposed direct potable reuse (DPR) criteria. The charge of the expert panel is to review the proposed criteria (regulations) for DPR and make a finding as to whether, in its expert opinion, the proposed criteria would adequately protect public health. Information about the expert panel is available on the State Water Board DPR website. NWRI administers the panel and facilitates the panel meetings and panel work.
Review of Definitions
Again from the introduction of the December 1, 2021 meeting, the following definitions are given about potable reuse:
Direct potable reuse is the planned introduction of recycled water either directly into a public water system or into a raw water supply immediately upstream of a water treatment plant. Please visit our website for additional information: Regulating Direct Potable Reuse in California | California State Water Resources Control Board
The image below shows the types of indirect (legal) and direct (not yet legal) potable reuse processes in California. Click here for a larger version.
Source: CA DPR Framework 2021
The following image is a simplified view of both Indirect Potable Reuse (Groundwater Recharge and Surface Water Augmentation) and Direct Potable Reuse (Raw Water Augmentation and Treated Water Augmentation).
DPR Concepts and Legislative History
A previous article reviewed concepts and legislative history in California and other states. Read that article here.
Status and Opening Remarks by Co-Chairs
James Crook and Adam Olivieri are the co-chairs of the Expert Panel. See entire panel here as well as the CA DPR staff participating in the development of the criteria.
The co-chairs reported that the Pathogen Working Group met in September 2021 starting preliminary work. The status of today will address the adequate protection of public health and the energy production required for conversion of processed wastewater into potable water. Note they reiterated that the pathogen removal section needed further clarification. Energy was not addressed in this session.
Agenda, List of Experts and Draft DPR Framework
Please click here for the agenda for the December 1, 2021 Expert Review of the DPR Criteria. To download the first draft of the criteria on which this review was based, click here. To review the framework, read this report from the first meeting announcing Public Comments on the DPR Framework: Toilet-to-tap Changes 100 Years of Public Health Policy
Statues for Raw Water Augmentation (RWA) and Treated Water Augmentation (TWA) Presented by Staff
As shown in the image displayed previously, RWA means the highly treated water leaves the wastewater plant via a pipeline and is delivered to a public drinking water treatment facility (DWTF) for more processing. TWA assumes the wastewater treatment is enough to achieve potability and the water is sent directly to the public drinking water distribution system. The experts debated if two sets of regulations were needed for RWA and TWA. Although the State Water Board (SWB) chose to develop one criteria for both RWA and TWA, the committee stated that RWA and TWA must be treated with consistent Public Health Risk Management.
Blending to Benefit the RWA Process
According to the staff presentation, blending reduces the need for Ozone/BAC treatment, a treatment that has been considered essential for removing CEC’s (contaminants of emerging concern). Read about Ozone/BAC here. The theory is that given enough clean water blended with the treated water, the amount of Ozone/BAC treatment (and thus cost) will be minimized; however, there was no discussion about the requirements and amount of clean water needed for blending. Blending also reduces the threat of low molecular weight chemicals escaping the RO (reverse osmosis) process.
Questions/Comments from Panelists to Staff
1) Two different calculations are needed for the case of microorganism versus chemicals in the wastewater, evidence for which has already been seen with virus in oxidation.
2) When blending two streams which include pathogens, which rule is to be used?
3) The proposed DPR regulation treatment technologies include membranes, RO and AOP. Why limit to three technologies? Staff said these are the types with the most experience.
Effect of DPR on Distribution Systems
This section was presented by Jing Chao, Senior Sanitary Engineer Distribution Systems. Please refer to the above chart to see the Distribution System in Treated Water Augmentation (TWA).
Regulations Governing Distribution System Water Quality: Lead and Copper Rule. PWS (Public Water System) must demonstrate optimum Corrosion Control and conduct Corrosion Control Study. Engineer Chao outlined the required steps in the Corrosion Control Study including number of samples and parameters required for study. The Lead and Copper Rule requires notification of water users when parameters exceed values considered safe. The statues also require lead line monitoring and replacement.
Regulations Governing Distribution System Water Quality: Total Coliform Rule. These are requirements to control bacterial growth. Different sample standards are required depending on the side of the water facility and number of clients served. Public notification is required for E.Coli exceedance detected.
Regulations Governing Distribution System Water Quality: Surface Water Treatment Rules. There is a requirement to maintain a disinfectant residual which is measured at various points along the line. HPC bacteria and Legionella are areas of concern. Hot Spots along the line must be identified.
Regulations Governing Distribution System: California Waterworks Standards. This covers materials, installations and upgrades to the physical distribution system.
Proposed Changes for DPR
The DIPPRA (Direct Potable Reuse Responsible Agency) and a public water system receiving advanced treatment water or finished water shall submit a Corrosion Control and Stabilization Plan to the State. At a minimum the plan shall include a plan for maintaining chemical and microbial stability in the drinking water distribution system.
Some Questions/Comments from Expert Panel for Staff
What is the rationale for different requirements for medium and small systems? These are just as exposed to risk as the large systems. Engineer Chao replied that this is a holdover from the 1990’s lead/copper rule and also a function of economics, presumably the monitoring is a financial burden on smaller systems.
How many systems in California might use DPR and also have lead service lines? Engineer Chao said she has never seen lead service lines in California.
How does blending with reuse and a second source change the blending ratios? Engineer Chao said that when two waters come together, the chemistry must be determined.
There is a major hole where DPR is serving a large population but segments will never have done corrosion control. All lengths of the pipeline must be investigated before DPR commences.
The statute 64683 should include temperature explicitly. Temperature should or could be considered a treatment.
Chad Plantenberg felt the draft regulations were adequate, but that the Human Right to water is not addressed nor is climate change. Small remote communities who will benefit most are not explicitly included in the regulations.
Jennifer West, Managing Director, WateReuse California, said the RWA and TWA presentation was good, but suggested extending the credits. For the Pathogen LRV requirement, they appreciate the addendum and further review of raw wastewater concentration of microbes not considered. Watereuse is a nationwide organization following water reuse issue in all states. Read detailed letter to staff about RWA and TWA.
Sheryl Hamlin asked if NWRI had an update on the pilot DPR project in Scottsdale Arizona and should the Arizona DPR Framework which was approved in 2018 be reworked to incorporate COVID? NWRI said they worked with Arizona in the 2015-2016 period and were aware of the project, but had no critical assessment. There was no response about Covid.
There will be two more meetings, one in January 2022 and one in February. Check the California DPR site for dates: https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/direct_potable_reuse.html
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