California develops regulations for the direct use of reclaimed water as drinking water

California is currently considering direct reclaimed water for drinking water (DPR) and plans to introduce reclaimed water directly into public water systems or directly upstream of water treatment plants as raw water supply
.
The California Water Board (SWB) is working on new regulations
.
This includes the publication of frameworks and standards for the use of reclaimed water as drinking water and the establishment of expert review panels to review proposed standards to ensure public health
.
The SWB identifies additional areas of investigation related to pathogen and chemical control to address data gaps
in the development of standards and regulations.
The regulatory process for the direct use of final reclaimed water as drinking water will be determined
by the SWB.

California has been a leader
in water recycling due to the water stress it faces.
Jeff Mosher outlined how the state plans to further this process by enacting regulations to cover reclaimed water directly for drinking water
.

California communities rely primarily on groundwater and surface water resources to meet their water needs
.
Over the decades, public water supplies have been mitigated
through the reuse of drinking water in groundwater recharge programs and, more recently, the increase in surface volume.
However, for future reclaimed water direct drinking water projects to be successful, communities are considering direct reclaimed water for drinking water (DPR), and they plan to introduce reclaimed water directly into the public water supply system or directly upstream of the water treatment plant as raw water supply to increase their drinking water supply
.
To meet the state's future demand for reclaimed water to be used directly as drinking water, the California Water Resources Control Board (SWB) is currently working on new regulations
.

The use of urban indirect reclaimed water for drinking water is being widely implemented in California, including new groundwater recharge and surface water expansion projects
.
In addition to traditional factors such as tight supply, population growth and competition for existing water supplies, other factors are driving significant increases in the state's water cycle, including more frequent and severe droughts, increasingly stringent sewage quality regulations, potential future discharge limits, a desire for a more sustainable One Water approach, and the need
to address climate resilience.

Direct use of reclaimed water as drinking water has been implemented in Texas and approved in Arizona
.
In addition, other states, including Colorado and Florida, are also working on regulations
for the direct use of reclaimed water as drinking water.
California began evaluating reclaimed water directly as drinking water as a viable method in 2010 and has steadily moved toward
formal regulation through a process that includes legislation and water utility support.
The Water Board is responsible for developing regulations
by assessing scientific, technical, and public health issues.
To this end, legislation has been passed that requires the direct use of reclaimed water as drinking water regulations to be completed
by 2023.

Current regulations on the use of reclaimed water as drinking water

California's provisions for reclaimed water for groundwater recharge and surface water expansion emphasize the use and benefits of environmental buffers in treatment, as well as providing response times
when treatment fails.

The California Groundwater Recharge Project was first implemented on a case-by-case basis in the late 1960s to strengthen barriers to coastal seawater intrusion and to recharge aquifers
.
The Los Angeles County Health District and Orange County Water District's long-running groundwater recharge projects provided operational experience that supported the adoption of the Groundwater Recharge Project (GRRP) Final Rule in 2014
.
Currently, the state's utilities are implementing a number of groundwater recharge projects
.

The Surface Water Augmentation (SWA) regulation was finalized in 2018 to allow surface water reservoirs
to be expanded with recycled water.
In SWA projects, pathogens
can be controlled through reservoirs, advanced treatment and drinking water treatment.
Currently, SWA's projects in California include the San Diego Water Purification Project, the East County Advanced Water Purification Project, and the Las Vegas-Triyunford Pure Water Project
.

GRRP and SWA regulations include standards to ensure public health protection for these programs, including:

Enhanced source control beyond standard preprocessors

Sewage treatment

Deep processing

Includes pathogen and chemical control water quality requirements

Monitor needs

SWA and GRRP projects require comprehensive advanced treatment (FAT), which includes reverse osmosis and advanced oxidation treatment processes
.

California reclaimed water is used directly as drinking water

Direct use of reclaimed water for drinking water, which involves the use of sewage as a drinking water source in the absence of a significant environmental buffer zone (e.
g.
, groundwater basins or large reservoirs), is a plan to introduce recycled water directly into the public water supply system or directly into the raw water supply upstream of the water treatment plant
.

In California, there are two forms of direct use of reclaimed water as drinking water: 1) Raw Water Expansion (RWA) – Figure 1, which plans to put circulating water into a pipe or aqueduct system to deliver raw water to a drinking water treatment plant to provide water to the public water supply system; 2) Treated Drinking Water Augmentation (TWA) - Figure 2, where it is planned to put circulating water into the distribution system of the public water supply system
.

Figure 1 Expansion of raw water

Figure 2 Expansion of drinking water after treatment

Reclaimed water is proposed as a drinking water framework

In accordance with the legislative mandate, SWB is developing standards, including the following:

• Release of reclaimed water for direct use as a drinking water framework

• Using the recommended reclaimed water for direct use as drinking water, research information is used to develop standards for the direct use of reclaimed water as drinking water

• Establish an expert review panel to review the proposed standards and ensure that they protect public health

Reclaimed water is used directly as drinking water research

In reviewing the feasibility of standards for direct use of reclaimed water as drinking water, the SWB identified additional areas of investigation related to pathogen and chemical control to address the data gaps
needed to develop standards and regulations for the direct use of reclaimed water in California.
SWB conducted the study in collaboration with the Water Research Foundation (WRF), which was used to develop standards
for the direct use of reclaimed water as drinking water.
Research projects include:

• Assess quantitative microbial risk and plant performance/reliability tools

• Measurement of pathogens in sewage

• Collection of pathogens from sewage during outbreaks

• Define potentially hazardous chemical peaks and management options

• Evaluation of analytical methods for detecting unknown chemical substances in circulating water

frame

SWB is responsible for developing the Direct Use of Drinking Water Regulations for Reclaimed Water in California and publishing, improving and revising the proposed regulatory framework for the Direct Use of Drinking Water in California (SWRCB 2018, SWRCB 2019, SWRCB 2021).

Based on the GRRP and SWA standards, the direct use of reclaimed water as a drinking water framework expands specific elements, but also includes some new requirements, including the following:

• A joint program that describes all partner agency roles

• Technical, administrative, financial capabilities

• Operator certification

• Wastewater source control

• Pathogen and chemical control

• Water Safety Program

• Additional monitoring and monitoring plans

• Engineering reports and operational plans

• Pathogen and chemical control point monitoring and response plans

• Cross-connect control

• Corrosion control and stabilization

• Public health surveillance

The direct use of reclaimed water as a drinking water framework and appendices, as well as other information, is available on the website of the Social Welfare Department at /drinking_water/certlic/drinkingwater/direct_potable_reuse.
html

Highlights of the proposed reclaimed water standard

The proposed standards in the framework for the direct use of reclaimed water as drinking water are very extensive
.
However, areas of high concern include pathogen and chemical control, as well as broad implementation requirements such as planning and reporting
.

The framework includes significantly higher requirements for water treatment processes and effluent quality
.
Advanced processing must include four unit processes (as opposed to three processes for GRRP and SWA).

The unit process must include three process mechanisms, including UV disinfection, physical separation, and chemical disinfection
.
In addition to the FAT (reverse osmosis and advanced oxidation) required for certain GRRP and SWA projects, ozone/bioactivated carbon
is required for reclaimed water directly used as drinking water.

Reclaimed water is used directly as drinking water, and pathogens require viral 20-log reduction (LRVs), Giardia 14 LRVs, and Cryptosporidium 15 LRVs
.
These logarithmic removals include reclaimed water being used directly as drinking water, and additional logarithmic reductions are addressed to address reliability issues
.

The direct use of reclaimed water as a drinking water framework includes extensive enforcement requirements
related to project development, initiation, compliance and reporting.

Potential problems with utilities

The proposed standard is presented in the framework for the direct use of reclaimed water as drinking water and the addendum and will be finalized by the SWB by the end of 2023
.
These criteria
are currently being reviewed by a panel of experts.
During this review, the Social Worker Bureau received comments
on the proposed standards.
Some of the areas in which comments were received include:

Distinguish between RWA and TWA
.
The proposed standard places the same requirements
on both RWA and TWA.
However, RWA content strengthens public health protections
.
Will these differences result in additional public health protections being counted in RWA?

Pathogen LRV requirements
.
Due to the use of additional logarithmic removal to address reliability issues, LRV is higher
than GRRP and SWA.
Can other measures be used to meet this need, such as innovation or backup monitoring and operational control?

Chemical control
.
Prior to FAT there were regulatory requirements for ozone/bioactivated carbon, which could inhibit innovation
.
Can I specify performance targets for additional processing?

Potential overlap in programs, programs, and reporting, and can these requirements be streamlined processes to support efficient reporting and regulatory oversight?

Finalize the regulatory process

SWB is currently working with a panel of experts to review the Direct Use of Reclaimed Water Framework and the criteria for Direct Use of Drinking Water proposed in the Addendum
.
The SWB asked the panel of experts to determine that these standards protect public health
.
Therefore, as part of the review process, the SWB may revise the proposed criteria
.
The panel will complete the review in 2022, while the SWB will finalize the DPR criteria
by December 2023 as planned.