Summary of Arizona's Water Reuse Guideline or Regulation for Direct Potable Water Reuse

This page is part of the EPA’s REUSExplorer tool, which summarizes the different state level regulations or guidelines for water reuse for a variety of sources and end-uses.
The source water for this summary is Treated Municipal Wastewater.

• Technical basis
• Types of planned water purification approved for use in Arizona
• Additional context and definitions
• Advanced water purification specifications (table)
• Upcoming state law or policy
• References
• Disclaimer

This page is a summary of the state's water reuse law or policy and is provided for informational purposes only. Please always refer to the state for the most accurate and updated information.

In Arizona, direct potable water reusepotable water reuseThe use of highly treated recycled water for drinking water purposes. This reuse application includes both indirect potable reuse through introduction of recycled water into an environmental buffer such as a surface reservoir or groundwater aquifer, and direct potable reuse through introduction of recycled water into a drinking water system. (DPR), referred to in Arizona's regulation as advanced water purification (AWP), applications include drinking water augmentation to either a drinking water treatment facility or a drinking water distribution system (Ariz. Admin. Code tit. 18, § R18-9-A801). The source of water (treated municipal wastewatertreated municipal wastewaterTreated wastewater effluent discharged from a centralized wastewater treatment plant of any size. Other terms referring to this source of water include domestic wastewater, treated wastewater effluent, reclaimed water, and treated sewage.) is specified by the state as municipal wastewater. The write-up uses state terms when discussing sources or uses of water that may differ from the Regulations and End-Use Specifications Explorer's (REUSExplorer's) terms.

Technical basis

Potable water in the United States must meet all applicable Safe Drinking Water Act (SDWA) requirements, including its implementing regulations (40 C.F.R. § 141) for chemical and microbial contaminants. Arizona requirements for direct potable reuse are provided in Ariz. Admin. Code tit. 18, § 9.

Arizona requires permits prior to the distribution of advanced treated water (Ariz. Admin. Code tit. 18, § R18-9-B806). Information regarding the application requirements can be found in Ariz. Admin. Code tit. 18, § R18-9-C816. Permits will be issued to Advanced Water Purification Responsible Agency (AWPRA) applicants if the applicant meets requirements of Title 18 Chapter 9, Article 8, Title 18 Chapter 4 Articles 1 and 2, and Title 18 Chapter 5, Article 5 (Ariz. Admin. Code tit. 18, § R18-9-C816).

For chemicals, there are three different tiers each with their own specific requirements. Tier 1 chemicals and specifications can be found in the Primary Drinking Water Maximum Contaminants Levels (MCLs) under 40 CFR § 141 Subpart G (Ariz. Admin. Code tit. 18, § R18-9-E825). Tier 2 chemicals include those that are used, stored, or discharged by non-domestic dischargers in the collection system as well as chemicals used at the water reclamation facility (WRF) and the advanced water treatment facility (AWTF). Further information on chemical analysis for each chemical can be found in Ariz. Admin. Code tit. 18, § R18-9-E826. Tier 3 chemicals consist of performance-based indicators which will be selected by an AWPRA applicant based on the requirements outline in Ariz. Admin. Code tit. 18, § R18-9-E827. Additionally, Arizona allows AWPRA applicants to select either a standard approach or site-specific approach for the management of total organic carbon. For the standard approach, water from a AWTF may not exceed 2 mg/L of TOC. Alternatively, for the site-specific approach, the AWPRA must conduct two procedures to establish the TOC limit. Refer to Ariz. Admin. Code tit. 18, § R18-9-F834 subsection C for more information.

For pathogens, the standard log reduction targets (LRTs) for enteric viruses (specifically norovirus), Giardia lamblia cysts, and Cryptosporidium oocysts are set at a 13-log reduction, 10-log reduction, and 10-log reduction, respectively. (Ariz. Admin. Code tit. 18, § R18-9-E828). The LRTs between raw wastewater and finished drinking water were calculated using a quantitative microbial risk assessment (QMRA) based approach with an annual benchmark risk 1 infection per 10,000 people (AWP: Technical Advisory Group, 2023; Pecson et al., 2022). Raw wastewater density information was based on Pecson et al. (2022) (AWP, 2023). A web-based tool, DPRisk (version 1.01; 11.05.2020), was used to evaluate QMRA scenarios (AWP, 2023). Dose response models included: the hypergeometric model for norovirus (Teunis et al., 2008); the exponential model for Giardia (Rose and Gerba, 1991; Eisenberg et al., 1996); and the beta-Poisson model for Cryptosporidium (Messner and Berger, 2016) (AWP, 2023). The water exposure ingestion volume assumed was 2.5 L/day (AWP, 2023).

Alternatively, an AWPRA applicant may select a site-specific LRT approach, which requires reference pathogen monitoring as part of the initial source water characterization (ISWA) plan based on the requirements of Ariz. Admin. Code tit. 18, § R18-9-C814 subsection (C)(3)(c). Site-specific LRTs will be calculated using the highest sample concentration of the pathogen over the monitoring period conducted for a minimum of 24 months. Additional information on the sampling protocol can be found in subsection C of Ariz. Admin. Code tit. 18, § R18-9-E828(Ariz. Admin. Code tit. 18, § R18-9-E828). The treated wastewater used in an AWP should receive continuous treatment and pathogen log reduction credits will be assigned for treatment barriers. At least one validated filtration treatment and one validated disinfection method determined through reference pathogen monitoring pursuant to subsection (C)(3)(c) of R18-9-C814 should target each of the reference pathogens. Each treatment process will be credited with a minimum of 0.5 pathogen log reduction credits; shall not be credited with more than 6 validated pathogen log reduction credits; and may receive pathogen log reduction credits for one or more pathogens. Blending is not eligible to receive pathogen log reduction credits or validated treatment log reduction values. Treatment processes that are credited with pathogen log reductions must be continuously tracked with a SCADA online monitoring system for surrogates and/or operational parameters.

Types of planned water purification approved for use in Arizona

Ariz. Admin. Code tit. 18, § R-18-9-A801 defines the following approved direct potable reuse applications:

• Advanced water purification: the introduction of advanced treated water directly into a drinking water treatment facility or distribution system of a public water system to consumers.

Additional context and definitions

All AWPRA applicants must develop an Initial Source Water Characterization plan, a Pilot Study Plan and pilot the pilot treatment train (Ariz. Admin. Code tit. 18, § R18-9-C815; Ariz. Admin. Code tit. 18, § R18-9-C815). Once awarded a permit, permittees are required to submit monthly monitoring results using the AWP online portal. Specific requirements for both pathogen and chemical control can be found in Ariz. Admin. Code tit. 18, § R18-9-E830. Additionally, AWPRA permittees must submit an annual report to the Department by March 30^th of each year (Ariz. Admin. Code tit. 18, § R18-9-E831).

Additional details on the following topics can be found within the following regulation sections:

• Definitions (§ R18-9-A801)
• General Requirements (§ R18-9-B806)
• Applicant Pathways (§ R18-9-C813)
• Initial Source Water Characterization (§ R18-9-C814)
• Pilot Study (§ R18-9-C815)
• Tier 1 Chemical Control; Maximum Contaminant Levels (§ R18-9-E825)
• Tier 2 Chemical Control; Advanced Water Purification-Specific Chemicals (§ R18-9-E826)
• Tier 3 Chemical Control; Performance-Based Indicators (§ R18-9-E827)
• Pathogen Control (§ R18-9-E828)
• Ongoing Monitoring Requirements (§ R18-9-E829)
• Reporting Requirements (§ R-18-9-E830)
• Annual Report (§ R18-9-E831)

As of October 2025, application of the rule is still in the developmental phases in Arizona. More information, including permitting flow charts and introductory guidance, can be found on the "See More" section on the right side of the Arizona Advanced Water Purification webpage (ADEQ, 2025b).

Advanced water purification specifications

Source = Ariz. Admin. Code tit. 18, § R18-9-A801 (pdf); Ariz. Admin. Code tit. 18, § R18-9-E828 (pdf); Ariz. Admin. Code tit. 18, § R18-9-E829 (pdf); Ariz. Admin. Code tit. 18, § R18-9-F834 (pdf); 40 C.F.R § 141.
SCADA = Supervisory Control and Data Acquisition System. 
aTier 1 chemicals include the chemicals listed in 40 CFR § 141 Subpart G.
bMonitoring for Tier 1 chemicals is performed quarterly except for TOC, nitrate, and nitrite (Ariz. Admin. Code tit. 18, § R18-9-E829).

Upcoming state law or policy

As of October 2025, ADEQ is still working on the implementation phase of the rule and is identifying ways to have the applicants demonstrate compliance with the rule. Future revisions to the rule may be required (ADEQ, 2025a).

References

ADEQ (Arizona Department of Environmental Quality). 2025a. Completed Rulemakings: Advanced Water Purification (previously DPR). https://azdeq.gov/awp-rulemaking

ADEQ. 2025b. Water Quality Division: Advanced Water Purification. https://azdeq.gov/awp

AWP: Technical Advisory Group. 2023. Advanced Water Purification (AWP): Technical Advisory Group (TAG) Recommendations. https://static.azdeq.gov/wqd/awp/tag_recommendations.pdf (pdf)

Eisenberg, J. N. S., Seto, E. Y. W., Olivieri, A. W., & Spear, R. C. (1996). Quantifying water pathogen risk in an epidemiological framework. Risk Analysis, 16(4), 549–563.

Messner, M. J., Berger, P. (2016). Cryptosporidium infection risk: results of new dose-response modeling. Risk Analysis, 36, 1969-1982.

Pecson, B. M., Darby, E., Danielson, R., Dearborn, Y., Di Giovanni., G., Jakubowski, W., Leddy, M., Lukasik, G., Mull, B., & Nelson, K. L. (2022). Distributions of Waterborne Pathogens in Raw Wastewater Based on a 14-Month, Multi-Site Monitoring Campaign. Water Research, 213: 118170. https://doi.org/10.1016/j.watres.2022.118170

Rose, J. B., & Gerba, C. P. (1991). Assessing potential health risks from viruses and parasites in reclaimed water in Arizona and Florida, USA. Water Science and Technology, 23(10/2), 20912098.

Teunis, P. F. M., Moe, C. L., Liu, P., Miller, S. E., Lindesmith, L., Baric, R. S., Le Pendu, J., Calderon, R. L. (2008). Norwalk virus: How infectious is it? Journal of Medical Virology, 80, 1468-1476.

National Primary Drinking Water Regulations, 40 C.F.R. § 141.

Water Pollution Control (pdf), Arizona Admin. Code tit. 18 § 9.

Safe Drinking Water (pdf), Arizona Admin Code tit 18 § 4.

Environmental Reviews and Certification (pdf), Arizona Admin. Code tit 18 § 5.

Disclaimers

Please contact us at waterreuse@epa.gov if the information on this page needs updating or if this state is updating or planning to update its laws and policies and we have not included that information on the news page.