Summary of Oklahoma'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 Oklahoma
- Water reuse treatment category for agriculture
- Additional context and definitions
- Water reuse for agriculture 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 Oklahoma, water reuse for water reuse for agricultureThe use of recycled water to land to assist in the production of both commercially and non-commercially processed food crops consumed by humans or livestock and non-food crops. Includes pasture for milking and non-milking animals, fodder, fiber, and seed crops, vineyards, orchards, ornamental nursery stock, Christmas trees, and silviculture. Excludes consumption by livestock, onsite non-potable reuse, and landscaping. includes drip irrigation on orchards or vineyards; spray or drip irrigation on sod farms; subsurface irrigation of orchards or vineyards; irrigation of livestock pasture; restricted access irrigation of sod farms; restricted access irrigation of fiber, seed, forage and similar crops; pasture irrigation for range cattle; irrigation of silviculture. The source of water 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 municipal wastewater. This 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
Oklahoma approves the reuse of reclaimed water for agricultural irrigation including subsurface and drip irrigation, irrigation for silviculture, irrigation of livestock pasture and restricted access irrigation of sod farms, pasture and fiber, seed, forage and similar crops (Okla. Admin. Code § 252:656). All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations, must be met in addition to any relevant rule requirements under the Food Safety Modernization Act (FSMA) (124 Stat. 3885). Oklahoma requires specific treatment for the reuse of reclaimed water for agriculture in areas where public access is expected. 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. The technical basis for developing the specifications and/or removals of microbial contaminants, chemicals and other relevant indicators was the product of a workgroup including regulatory agencies, local consultants and national water reuse experts (Oklahoma DEQ, personal communication, May 31, 2022).
Water reuse for agriculture approved for use in Oklahoma
Okla. Admin. Code § 252:656-27 defines the following approved water reuse for agriculture:
- Drip irrigation on orchards or vineyards (Category 2)
- Spray or drip irrigation on sod farms (Category 2)
- Subsurface irrigation of orchards or vineyards (Category 3)
- Irrigation of livestock pasture (Category 3)
- Restricted access irrigation of sod farms (Category 3)
- Restricted access irrigation of fiber, seed, forage and similar crops (Category 5)
- Pasture irrigation for range cattle (Category 5)
- Irrigation of silviculture (Category 5)
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 2 reclaimed water, the treatment requirements are secondary treatment, nutrient removal, coagulation, filtration, continuous turbidity measurements using online turbidimeters and disinfection by chlorination or a combination of chlorination and UV. The method of disinfection shall achieve 5-log removal of Adenovirus type 15, 5-log removal of Salmonella typhimurium and 3-log removal of Giardia lamblia.
- For Category 3 reclaimed water, the treatment requirements are secondary treatment, nutrient removal and disinfection by chlorination.
- For Category 5 reclaimed water, the treatment requirements are primary treatment through a wastewater lagoon system. Specific details about the design and construction of the primary wastewater treatment (lagoon system) are included in the Oklahoma administrative code (Okla. Admin. Code § 252:656-11 and Okla. Admin. Code §252:656-25-2(g) and (h)), which are intended to ensure a certain level of primary wastewater treatment.
For agricultural irrigation with Category 5 reclaimed water, Oklahoma provides suppliers with a list of restrictions. Suppliers should not irrigate with Category 5 reclaimed water:
- From a lagoon cell that receives raw sewage
- From any cell other than the one specified in the permit
- On any food crop that may be consumed raw
- On grain crops such as corn, wheat and oats, less than 30 days before harvest
- At rates that allow a discharge from the permitted water reuse site
- Within 100 feet of the permitted boundary of the site
- At a rate that exceeds the nitrogen and phosphorus rates for the crop grown at the site
- At a rate that results in phytotoxicity
- During periods of precipitation or while the soil is saturated or frozen
- On land having a slope greater than 5 percent
- Where there are berms or other barriers on a water reuse site that would cause the pooling or ponding of reclaimed water at the water reuse site (there should be no berms or barriers impede the natural flow of stormwater from the site)
Additional context and definitions
Oklahoma defines reclaimed water as “wastewater that has gone through the various treatment processes to meet specific water quality criteria with the intent of being used in a beneficial manner” (Okla. Admin. Code § 252:656). Silviculture is defined as the practice of controlling the growth, composition/structure and quality of forests to meet values and needs, specifically timber production (USFS, 2014).
Oklahoma requires that municipal reclaimed water permittees prevent any physical connections between reclaimed water lines and public water supply lines (Okla. Admin. Code § 252:656). Separation distances are required from public wells (300 feet), private wells (50 feet), waters of the state (25 feet for Category 2 reclaimed water and 50 feet for Categories 3 and 4 reclaimed water) and property lines (20 feet for Category 2 reclaimed water and 100 feet for Categories 3 and 4 reclaimed water). As of July 2012, all reclaimed water piping, valves and outlets are required to be colored purple and must be embossed or stamped on opposite sides every three feet with warning language that includes “CAUTION: RECLAIMED WATER – DO NOT DRINK.” For reclaimed water systems installed prior to July 2012, there must be, at minimum, above-ground signs containing the warning language in the previous sentence along with the international “Do Not Drink” symbol every 300 feet, at every change in direction, in the road easement on both sides of every road crossing and at every outlet. All Category 5 reclaimed water land application sites shall be fenced to prevent unauthorized entry (Okla. Admin. Code § 252:656).
Water reuse for agriculture specifications
Summary of Oklahoma's Water Reuse for Agriculture Specifications
| Recycled Water Class/Category (Approved Uses) | Source Water Type | Water Quality Parameter | Specification | Sampling/Monitoring Requirements (Frequency of monitoring; site/ location of sample; quantification methods)* |
|---|---|---|---|---|
|
Category 2 (Drip irrigation on orchards or vineyards; Spray or drip irrigation on sod farms) |
Municipal wastewater |
Turbidity |
≤2 NTU (daily average) ≤2 NTU (> 5% of daily maximum per month) ≤10 NTU (single sample maximum) |
Continuous monitoring. The daily mean operating filter effluent turbidity (continuously monitored) is calculated as the average of turbidity measures at ≤ 1.2-hour intervals over 24 hours and must be reported monthly. The maximum 24-hour turbidity must be based on highest measure from continuous monitoring taken at ≤ 1.2-hour intervals over 24 hours. |
|
Chlorine residual (at POEa to distribution system) |
≥1.0 ppm (free available chlorine residual) or “the chlorine residual at the POE shall be at a level to prevent growth of slime and regrowth of pathogens in the distribution and storage systems as determined by an approved chlorine decay rate model pursuant to OAC 252:656-3-4 (b)(7)(C)” |
Continuous monitoring |
||
|
Chlorine residual (at end-of-pipe) |
≥0.20 mg/L (free available chlorine residual) or ≥0.50 mg/L (combined chlorine residual) |
Daily |
||
|
Fecal coliform |
0 CFU/100 mL (in four of the last seven daily samples) ≤23 CFU/100mL (single sample maximum) |
Daily |
||
|
Total Nitrogen |
"≤ most stringent agronomic rate" |
Monthly |
||
|
Total Phosphorus |
"≤ most stringent agronomic rate" |
Monthly |
||
|
5-day carbonaceous biochemical oxygen demand (CBOD5) |
<5 mg/L |
Weekly |
||
|
Adenovirus type 15 |
5-log removal or inactivation |
The method of disinfection must achieve these removals |
||
|
Salmonella typhimurium |
5-log removal or inactivation |
|||
|
Giardia lamblia |
3-log removal or inactivation |
|||
|
Category 3 (Drip or subsurface irrigation of orchards and vineyards; Irrigation of livestock pasture; Restricted access irrigation of sod farms) |
Municipal wastewater |
Chlorine residual |
≥0.20 mg/L (free available chlorine residual) or ≥0.50 mg/L (combined chlorine residual) |
Every 12 hours, measured at the POE |
|
Fecal coliform |
<200 coli/100 mL (monthly geometric mean) <400 coli/100 mL (single sample maximum) |
3 times/week |
||
|
Total Nitrogen |
"≤ most stringent agronomic rate" |
Monthly |
||
|
Total Phosphorus |
"≤ most stringent agronomic rate" |
Monthly |
||
|
5-day biochemical oxygen demand (BOD5) or 5-day carbonaceous biochemical oxygen demand (CBOD5) |
<20 mg/L |
Weekly |
||
|
Category 5 (Restricted access irrigation of fiber, seed, forage and similar crops; Restricted access pasture irrigation for range cattle; Silviculture) |
Municipal wastewater |
Dissolved oxygen (DO) |
>2.0 mg/L |
Weekly |
|
Nitrogen |
Not specified |
Not specified |
||
|
Phosphorus |
Not specified |
Not specified |
Source= Okla. Admin. Code § 252:656 and § 252:627
* 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 POE = point of entry
Upcoming state law or policy
No upcoming regulations pertaining to water reuse for agriculture were found for Oklahoma.
References
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
Food Safety Modernization Act (FSMA), 124 Stat. 3885.
Lagoon Standards, Okla. Admin. Code § 252:656-11.
Operation and Maintenance of Water Reuse Systems, Okla. Admin. Code § 252:627.
Slow Rate Land Application Design, Okla. Admin. Code §252:656-25-2.
United States Forest Service (USFS). 2014. Forest Management: Silvacultural Practices.
Wastewater Reuse, Okla. Admin. Code § 252:656-27.
Water Pollution Control Facility Construction Standards, Okla. Admin. Code § 252:656.
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.