Summary of Colorado's Water Reuse Guideline or Regulation for Agriculture

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.

On this page:

• Technical basis
• Water reuse for agriculture approved for use in Colorado
• Water reuse treatment category for agriculture
• Additional context and definitions
• Water reuse for agriculture specifications (table)
• Upcoming state law or policy
• References
• Disclaimer

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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 Colorado, water reuse for agriculture includes irrigation of non-food crops and silviculture, non-edible and edible hemp and resident-controlled food crops; commercial food crop growing operations; and non-commercial food crop growing operations. The source of water (treated municipal wastewater) treated municipal wastewater Treated 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 domestic 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

Colorado approves the use of reclaimed water for agricultural irrigation including crops not grown for human consumption, non-commercial food crop growing operations, commercial food crop growing operations and edible and non-edible hemp (5 Code Colo. Regs. § 1002-84). All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations must be met. Additionally, commercial food crop growing operations may be subject to any relevant rule requirements under the Food Safety Modernization Act (FSMA) (124 Stat. 3885). Treatment requirements and performance standards are applied for the removal of microbial contaminants, chemicals and other relevant indicators related to agriculture and are summarized in the table. Each category of reclaimed water has E. coli, turbidity and TSS specifications. Category 3 Plus meets the standards of Category 3 and additional treatment includes virus removal (5-log reduction of enteric viruses) and specific filtration treatment. The technical basis for this virus reduction is the California Title 22 minimum requirement of 5 log virus treatment for indoor uses of reclaimed water. The Commission found that the virus inactivation tables published by EPA are appropriate when chemical disinfection is used (log inactivation of viruses to be determined as referenced in 5-CCR-1002-11 and defined by EPA for disinfection of surface water - Hepatitis A). If UV disinfection is employed, virus disinfection should be measured against Hepatitis A for chemical disinfection or 40 mJ/cm² for ultraviolet light disinfection (EPA, 2006).

Reclaimed water (Categories 1, 2 and 3) have E. coli specifications based on EPA’s 1986 Ambient Water Quality Criteria (AWQC). The decision to use the 1986 AWQC was made in 2000, prior to EPA’s 2012 updates. While the approved Category 1, 2 and 3 uses do not directly correlate to swimming, the Water Quality Control Commission assumed criteria established to protect swimmers will be more protective than individuals “casually exposed” to reclaimed domestic wastewater (5 Code Colo. Regs. § 1002-84). For Category 3 uses, the E. coli standard is 75% non-detect and not to exceed 126/100 mL in monthly samples, due to the higher risk of unintended cross connections and public contact (5 Code Colo. Regs. § 1002-84). Turbidity is also used as a surrogate measure of “microbial purity” (in regard to viruses and parasites) in reclaimed domestic wastewater. A “middle ground” of 5 NTU (in more than 5% of results per month) was selected for the application of reclaimed domestic wastewater (5 Code Colo. Regs. § 1002-84). 

Water reuse for agriculture approved for use in Colorado

5 Code Colo. Regs. § 1002-84 defines the following approved water reuse for agriculture of reclaimed water treated by centralized reclaimed water systems: 

• Irrigation of non-food crops and silviculture (Category 1)
• Irrigation of non-edible hemp (i.e., hemp used for cover crop, fiber and other products not for human consumption) (Category 1)
• Commercial food crop growing operations (Category 2)
• Irrigation of resident-controlled food crops (Category 3 Plus)
• Non-commercial food crop growing operations (Category 3 Plus)
• Irrigation of edible hemp (i.e., industrial hemp seeds, oils, flowers and other hemp materials used to make edible products, dermal products and internal use products for human and animal consumption) (Category 3 Plus)

Treatment standards for water reuse for agriculture are the same for both centralized municipal and onsite water sources in Colorado. The same applications are housed in the onsite non-potable reuse webpage for reclaimed water treated by localized systems whereas this webpage focuses on use of recycled water from centralized systems.

Water reuse treatment category for agriculture

The various classes of treatment are defined by their respective treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized regarding water reuse for agriculture:

• For Category 1 reclaimed water, the treatment requirements are secondary treatment with disinfection. Category 1 water has an E. coli requirement of ≤126 E. coli/100 mL (monthly geometric mean) and ≤235 E. coli/100 mL (single sample maximum).
• For Category 2 reclaimed water, the treatment requirements are secondary treatment with filtration and disinfection. Category 2 water has an E. coli requirement of ≤126 E. coli/100 mL (monthly geometric mean) and ≤235 E. coli/100 mL (single sample maximum).
• For Category 3 Plus reclaimed water, the treatment requirements are secondary treatment with filtration and disinfection.

The filtration must be performed with conventional filtration; direct filtration; membrane, bag or cartridge filtration (in accordance with 5 Code Colo. Regs. § 1002-11); or alternative filtration technologies that are third-party tested to reliably remove 99.9% of challenge particles that are 3 microns at most. The disinfection must provide a minimum 5-log inactivation of viruses using either free chlorine or monochloramines, or a minimum UV of 40 mJ/cm². Category 3 water has an E. coli requirement of zero detections in the last 75% of samples (each calendar month) and ≤126 E. coli/100 mL (single sample maximum).

Additional context and definitions

In Colorado, reclaimed water is defined as “domestic wastewater that has received secondary treatment by a domestic treatment works (centralized or localized system) and such additional treatment as to enable the wastewater to meet the standards for approved uses” (Colorado WQCC, 2007). This summary focuses on domestic wastewater treated by centralized systems; the domestic wastewater treated by localized (on-site) systems is discussed in a separate EPA summary for onsite non-potable reuse applications.

Colorado defines “non-commercial food crop growing operation” as any operations growing food crops that are not considered a “covered farm” under the Food Safety Modernization Act, Produce Safety Rule, 21 CFR 112.4 (Colorado WQCC, 2020). Colorado defines “resident-controlled food crop irrigation” as irrigation of vegetables, fruits and other food crops located on the property dedicated to a single residential property (e.g., the garden for a single residence such as a house, row home or duplex) (Colorado WQCC, 2020).

Domestic reclaimed water users must notify the public via sufficiently sized signs in all use areas, tanks and other equipment used for storage or distribution of reclaimed domestic wastewater that warn that reclaimed water is being used and is not safe for drinking (5 Code Colo. Regs. § 1002-84). All new or replaced piping, valves, outlets and other appurtenances must be marked to differentiate reclaimed water from potable water or other piping systems. An approved cross connection control device or method must be provided at all potable water service connections to reclaimed water use areas. Irrigation equipment that is used with reclaimed water cannot be hooked up to potable spigots. Colorado mandates multiple practices, measures and conditions to be implemented while using reclaimed water for agricultural applications that are contingent upon level of public and environmental exposure and risk.

Water reuse for agriculture specifications

Summary of Colorado's Water Reuse for Agriculture Specifications

Source= 5 Code Colo. Regs. § 1002-84; Colorado WQCC (2007)

* Information about sampling and monitoring requirements such as frequency, site and quantification methods not specifically listed in the table was not explicitly specified in the State-specific regulations.

^a Grab or composite samples may be used for TSS.

Upcoming state law or policy

No upcoming regulations pertaining to water reuse for agriculture were found for Colorado.

References

Clean Water Act, 33 U.S.C. §§ 1251 et seq.

Colorado Department of Public Health and Environment Water Quality Control Commission (WQCC). 2007. WQCC Water Quality Policy (WQP) - 25 Monitoring and Reporting Requirements for Reclaimed Water Treatment Facilities.

Colorado Primary Drinking Water Regulations, 5 Code Colo. Regs. § 1002-11.

Colorado Water Quality Control Division (WQCD). 2007. Water Quality Permits – Guidelines for the Determination of Agronomic Rate for Application of Reclaimed Water Under Colorado Regulation No. 84.

Environmental Protection Agency (EPA), 1986. Ambient Water Quality Criteria for Bacteria (AWQC).

Environmental Protection Agency (EPA). 2006. Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule (pdf) (8.26 MB, November 2002, EPA 815-R-06-007) .

Food Safety Modernization Act (FSMA), 124 Stat. 3885.

Reclaimed Water Control Regulation, 5 Code Colo. Regs. § 1002-84.

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Disclaimers

Please contact us at [email protected] 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.