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California Direct Potable Reuse Regulations
What Are California Direct Potable Reuse Regulations
Direct potable reuse requirements are found in the California Code of Regulations at Title 22, Division 4, Environmental Health, Chapter 17, Surface Water Treatment, Article 10, Direct Potable Reuse.
In the California Code of Regulations (C.C.R), a “Direct potable reuse project” or “DPR project” means a project involving the planned introduction of recycled water that meets the requirements of this Article either directly into a public water system or into a raw water supply immediately upstream of a water treatment plant.
Regulatory Authority and Where DPR Requirements Are Codified
California’s DPR regulations can be found at Browse – California Code of Regulations. Utilities and agencies interested in developing or operating DPR projects should review all Direct Potable Reuse regulations. This article focuses on sections addressing wastewater source control, pathogen control, chemical control, monitoring, and reporting.
Wastewater Source Control (22 CCR § 64669.40)
Public Health Protection and Wastewater Collection System Requirements
Because the source water for DPR is municipal wastewater, the ultimate and most important goal of wastewater source control is protection of public health. Protection must begin in the wastewater collection system. Wastewater originates from domestic, commercial, and industrial sources, and additional measures are required to prevent or minimize the discharge of pollutants into wastewater that will be used for a DPR project.
This section addresses the controls necessary to protect the wastewater source.
Direct Potable Reuse Responsible Agency Responsibilities
The Direct Potable Reuse Responsible Agency (DiPRRA):
- Is responsible for compliance with waste discharge requirements of the California Code of Regulations
- Has an industrial pretreatment program and a pollution source control program, along with the authority to enforce them
- Has documentation demonstrating that local limits are established and submitted to the State Water Board
Early Warning Systems for Wastewater Source Protection
There must be a system to provide early warning of discharges to the wastewater collection system that could cause pass through or interference with DPR treatment processes. This system should include:
- Online monitoring that measures indicator compounds or surrogate parameters
- Notification processes from industrial pretreatment and source control programs to the DiPRRA regarding contaminants that may interfere with treatment processes
- Tracking of county public health disease surveillance programs and community raw wastewater disease surveillance programs to identify potential disease outbreaks
- Other early warning systems necessary to ensure public health protection.
The Wastewater Source Control regulations can be found at View Document – California Code of Regulations.
Pathogen Control Requirements (22 CCR § 64669.45)
Required Pathogen Log Reduction Performance Standards
Under California DPR regulations, the DPR treatment train must be designed to meet the following validated pathogen log reduction requirements:
- 20 log reduction for enteric viruses
- 14 log reduction for Giardia lamblia cysts
- 15 log reduction for Cryptosporidium oocysts
Treatment Train Design and Diversity Requirements
The treatment train must consist of four separate treatment processes for each pathogen, with each process capable of achieving at least 1.0 log reduction and no single process credited with more than 6.0 log reduction.
Additionally, the treatment train must include at least three diverse treatment processes. These processes must include:
- One membrane physical separation process
- One chemical inactivation process
- One ultraviolet (UV) inactivation process
Each treatment mechanism must be credited with no less than 1.0 log reduction.
Validation Studies and State Board Approval
Inactivation performance must be demonstrated through a validation study conducted at pilot scale or full scale. The validation study protocol must be approved by the State Water Board.
Continuous Monitoring and SCADA Based Compliance Demonstration
Because pathogen analytical results have significant lag times, continuous monitoring is required to ensure timely protection of public health. The DiPRRA must demonstrate compliance with pathogen log reduction values through continuous monitoring of surrogates and/or operational parameters using a SCADA system.
The treatment train must continuously achieve at least:
- 16 log reduction of enteric viruses
- 10 log reduction of Giardia lamblia cysts
- 11 log reduction of Cryptosporidium oocysts
If these minimum values are not met, the DiPRRA must notify the State Board and shut down the treatment train or divert finished water until the issue is resolved.
If the DiPRRA cannot continuously meet the full required log reductions of 20 (enteric viruses), 14 (Giardia lamblia cysts, and 15 (Cryptosporidium oocysts at least 90 percent of the time, corrective action is required.
Operational Response and Corrective Action Thresholds
The DiPRRA must propose pathogen control points, operational parameters, and critical limits to demonstrate that treatment processes and the overall treatment train are functioning properly.
See the Pathogen Control regulations at View Document – California Code of Regulations.
Chemical Control Requirements (22 CCR § 64669.50)
Required Treatment Processes and Treatment Diversity
Chemical control follows an approach similar to pathogen control. The DiPRRA must identify at least three separate treatment processes using at least three diverse treatment methods. These processes must include ozone with biologically active carbon (BAC), reverse osmosis, and advanced oxidation.
Minimum Chemical Removal Performance Criteria
Chemical treatment processes must achieve the following minimum performance standards:
- Ozone treatment must demonstrate at least 1.0 log reduction of carbamazepine and sulfamethoxazole
- Biologically active carbon must demonstrate at least 1.0 log reduction of acetone and formaldehyde
- Reverse osmosis (RO) must achieve an average sodium chloride rejection of 99.2 percent and total organic carbon, in the RO effluent, no greater than 0.5 mg/L in at least 99.5 percent of samples
- Advanced oxidation must achieve at least 1.0 log reduction of 1,4 dioxane
Validation Studies and Performance Approval
The performance of all chemical treatment processes must be validated through a validation study approved by the State Water Board.
Chemical Control Points, Surrogates, and SCADA Monitoring
The DiPRRA must establish chemical control points monitored using surrogates or operational parameters with critical limits. At least one control parameter must be capable of continuous online monitoring through a SCADA system with alarms to allow timely corrective action.
The DiPRRA must continuously monitor surrogates and operational parameters through the SCADA system, with alarms triggered when critical limits are exceeded.
Process Failure Response and Finished Water Protection
There must be sufficient mixing or storage within the treatment train or prior to finished water distribution to allow for diversion or shutdown in the event of a treatment process failure.
See Chemical Control regulations at View Document – California Code of Regulations.
Regulated Chemicals and Physical Characteristics Monitoring (22 CCR § 64669.60)
Required Monitoring Locations
Monthly sampling is required at the following locations:
- At the end of secondary wastewater treatment before entering the DPR project
- After the advanced oxidation process
- Finished water prior to the entry point to the distribution system
Monthly and Weekly Sampling Requirements
Samples must be analyzed for primary MCLs, secondary MCLs, action levels, and physical characteristics. See Title 22, Division 4, Chapter 15 at Browse – California Code of Regulations).
Weekly finished water samples must be collected for nitrate, nitrite, nitrate plus nitrite, perchlorate, and lead.
Exceedance Response, Notification, and Corrective Action
If an MCL is exceeded, a confirmation sample must be collected within 24 hours. If the average of the initial and confirmation samples exceeds the MCL, the DiPRRA must notify the State Board, partner agencies, and the public within 24 hours and initiate corrective action, including diversion or shutdown if necessary.
Regulated Chemicals and Physical Characteristics Control and Monitoring regulations may be found at View Document – California Code of Regulations (22 CCR § 64669.60).
Additional Chemical Monitoring Requirements (22 CCR § 64669.65)
Chemicals Subject to Additional Monitoring
This section requires monthly monitoring at the same locations under 22 CCR § 64669.60 for the following chemicals:
- Priority toxic pollutants identified at 40 CFR 131.38 at eCFR :: 40 CFR 131.38 — Establishment of numeric criteria for priority toxic pollutants for the State of California.;
- Chemicals with California notification levels;
- The following solvents: acetone; N,N-dimethylacetamide; methanol; and methyl ethyl ketone;
- Treatment precursor byproducts and treatment byproducts;
- Chemicals associated with business or household sources of hazardous substances, pharmaceuticals, and personal care products; and
- Any other chemicals specified by the State Board that may pose a human health risk.
- If the results of monitoring shows levels of these chemicals greater than levels that are not known to have human health implications or exceed notification levels, additional actions shall be taken including taking confirmation samples, notification of the State Board and partner agencies, and shut down of the process or diversion of finished waters.
- Additional Chemical Monitoring regulations can be found at View Document – California Code of Regulations.
Pathogen and Chemical Control Point Monitoring and Response (22 CCR § 64669.85)
Overview of Pathogen and Chemical Control Point Monitoring
This section addresses continuous monitoring of surrogate and/or operational parameters at pathogen and chemical critical control points to ensure critical control limits are being met and, if not, the implementation of measures and response times to address exceedances.
Pathogen and Chemical Control Point Monitoring and Response regulations can be found at View Document – California Code of Regulations.
Continuous SCADA Monitoring Requirements
Surrogate and operational parameters must be capable of continuous monitoring through a SCADA system. Parameters that cannot be continuously monitored are considered inadequate for evaluating compliance.
Acute and Chronic Exposure Definitions and Thresholds
The surrogates or operational parameters for acute exposures shall be able to demonstrate that treatment processes are meeting, at a minimum, 16 log reduction of enteric viruses, 10 log reduction of Giardia lamblia cysts, and 11 log reduction of Cryptosporidium oocysts. They must also demonstrate compliance with MCLs for nitrate, nitrite, and nitrate plus nitrite, and the TOC critical limit of 0.5 mg/L.
A chronic exposure is determined to have occurred if for more than 10 percent of the time a treatment process is not producing water that meets critical limits for more than two consecutive months. An explanation of the activities that must occur in the case of a chronic exposure exceedance are found at 22 CCR § 64669.85(c).
Treatment Train Diversion and Response Time Considerations
The treatment flow path shall be designed to include locations where treated water that does not meet critical limits can be diverted so that it is not distributed to the public.
Response times must take into consideration the time it takes for a monitoring device to send a signal to a SCADA system, the time required for the SCADA system to recognize a measurement as an exceedance of a critical limit and issue an alarm, and the time it takes operational personnel to react to the alarm and or for an automatic shutoff or diversion to take place.
SCADA System Functional and Cybersecurity Requirements
SCADA systems of all water treatment plants that are part of the DPR project must include the following:
- Provide alarms to the operator if pathogen or chemical limits are not being met;
• Identify trending degradation and significant excursions from water quality to allow operators to respond;
• Communicate and interoperate with SCADA systems of all treatment plants in the DPR project;
• Be secured and protected from cyberattack; and
• Be tested following the operations plan protocol.
Pathogen and Chemical Control Point Monitoring and Response regulations can be found at View Document – California Code of Regulations.
Compliance Reporting Requirements (22 CCR § 64669.95)
Overview of Monthly Compliance Reporting
This section describes the monthly data and information that must be submitted to the State Board by the 10th day of the following month summarizing treatment train performance and compliance monitoring.
Monthly Reporting Content and Submission Deadlines
The Direct Potable Reuse Responsible Agency shall submit monthly compliance reports by the 10th day of the following month.
Reports must summarize pathogen and chemical performance, treatment process data, excursions, corrective actions, equipment failures, calibration records, investigations, wastewater source control activities, detected chemicals, cross connections, and water quality complaints.
The DiPRRA shall submit the analytical results to the State Board or have the laboratory submit the results.
Required Monthly Reporting Elements
Monthly compliance reports shall include the following:
- A summary of overall treatment train pathogen LRV performance;
• A summary of overall treatment train chemical control performance;
• A summary of individual treatment process performance monitoring data;
• The date, duration, and cause of each occurrence of LRV performance below 20 log for enteric virus, 14 log for Giardia lamblia cyst, and 15 log for Cryptosporidium oocyst;
• A summary of control points that did not meet a critical limit established to assure proper ongoing performance of a treatment process pursuant to sections 64669.45 (Pathogen Control) and 64669.50 (Chemical Control), including dates and descriptions of failures of a critical limit, duration of failure, and description of corrective actions taken;
• A summary of excursions of operational parameters outside approved operating envelopes;
• Information pursuant to section 64664 (Monthly Report);
• Descriptions of violations of sections 64669.85(b) and (c) (Pathogen and Chemical Control Point Monitoring and Response);
• Calibration records for instruments that monitor pathogen or chemical control points;
• Dates and descriptions of major equipment and process failures and corrective actions taken;
• Dates and summary of testing of the treatment control and alarm system consistent with the protocol in the operations plan;
• Investigation or incident reports required to be prepared pursuant to sections 64669.45, 64669.50, 64669.60 (Regulated Chemicals and Physical Characteristics Control and Monitoring), and 64669.65 (Additional Chemical Monitoring);
• A summary of activities of the wastewater source control program conducted pursuant to section 64669.40;
• A summary of chemicals detected as a result of monitoring conducted pursuant to sections 64669.60 and 64669.65;
• Investigation or incident reports regarding a cross connection; and
• A summary of water quality complaints and reports of gastrointestinal illness received from customers.
More details can be found at View Document – California Code of Regulations.
Annual Reporting Requirements (22 CCR § 64669.100)
This section summarizes the activities of the DiPRRA over a single year. It is due to the State Board and partners receiving DPR water no later than six months after the end of the year. The details are described here View Document – California Code of Regulations.
Application of the SAMS Platform Within California Direct Potable Reuse Programs
California’s Direct Potable Reuse regulations require documentation, monitoring, response, and reporting across multiple program areas, including wastewater source control, pathogen control, chemical control, and compliance reporting. The regulations also require that records related to monitoring results, exceedances, corrective actions, and program activities be retained and made available to the State Board.
The SAMS platform is a data management system used by utilities and programs to store, organize, and retrieve regulatory and operational records. Within the context of Direct Potable Reuse programs, SAMS can be used to record industrial pretreatment and source control activities, maintain documentation associated with pathogen and chemical control points, and retain monitoring and response records referenced in 22 CCR § 64669.40 through 64669.85.
SAMS also provides structured data fields for capturing monitoring results, operational observations, and compliance documentation that may be required for monthly and annual reports submitted under 22CCR § 64669.95 and 64669.100. The platform functions as a system of record and does not replace treatment processes, monitoring equipment, or regulatory oversight.
For additional information, EPA has prepared a good Summary of California’s Direct Potable Reuse Specifications at Summary of California’s Water Reuse Guideline or Regulation for Direct Potable Water Reuse | US EPA. The table is a good outline of the requirements.
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About The Author
At NJBSoft, we’re proud to collaborate with experts like Robert Hollander, P.E., whose extensive experience in water quality and regulatory compliance allows us to design SAMS in order to meet industry needs. Bob’s leadership and deep industry knowledge supports utilities in staying organized, compliant, and focused on protecting public health every day.
Robert Hollander
- 45 years of experience in water quality, regulatory compliance, and utility management
- President of Hollander Consulting Services
- Held senior roles at the City of Peoria, City of Phoenix, and the Arizona Department of Environmental Quality
- Served as President of the AZ Water Association and the Western Coalition of Arid States
- Licensed Professional Engineer in Arizona with multiple Grade 3 operator certifications
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