Summary of Hawai'i'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.
- Technical basis
- Water reuse for agriculture approved for use in Hawai'i
- 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 Hawai'i, water reuse for includes all agricultural irrigation via spray, surface drip or subsurface drip irrigation; agricultural cleaning to wash down animals; surface drip or subsurface drip irrigation for sod farms and ornamental plants for commercial use; subsurface drip irrigation for above-ground food crops where the edible portion of the crop has minimal contact with recycled water; drip or subsurface drip irrigation for non-edible vegetation in areas with limited public access; fodder, fiber and seed crops not consumed by humans; and timber and trees not bearing food crops. 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. 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
Hawai'i approves the use of recycled water for agriculture, including spray, surface drip or subsurface drip irrigation and agricultural cleaning (Hawai'i State DOH, 2016b). 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. Hawai'i used California’s Title 22 Water Recycling Criteria (Cal. Code Regs. tit. 22) to determine acceptable filtration and disinfection units. The technical basis for other specifications and/or removals of microbial contaminants, chemicals and other relevant indicators is not explicitly specified.
Water reuse for agriculture approved for use in Hawai'i
Hawai'i State DOH (2016b) defines the following approved water reuse for agriculture:
- All agricultural irrigation via spray, surface drip or subsurface drip irrigation (R-1)
- Agricultural cleaning to wash down animals such as cattle, livestock, animal pens and housing (R-1)
- Surface drip or subsurface drip irrigation for sod farms and ornamental plants for commercial use (R-2)
- Subsurface drip irrigation for above-ground food crops (such as fruit trees) where the edible portion of the crop has minimal contact with the recycled water (R-2)
- Drip or subsurface drip irrigation for non-edible vegetation in areas with limited public access; fodder, fiber and seed crops not consumed by humans; and timber and trees not bearing food crops (R-3)
Water reuse treatment category for agriculture
The various classes of treatment for recycled water are defined by their level of treatment (Hawai'i State DOH, 2016b).
- For R-1 recycled water, wastewater must be oxidized, filtered and disinfected. The limits specified in the table are set based on system size. Filtration standards are based on the specific technology used.
- Disinfection may be achieved by chlorination, UV or another method that, when combined with filtration, has demonstrated inactivation and/or removal of 99.999% of plaque-forming units of F-specific bacteriophage MS2, polio virus or another virus that is at least as resistant to disinfection as the polio virus.
- For R-2 recycled water, wastewater must be oxidized and disinfected. The limits specified in the table are set based on system size.
- Disinfection may be achieved by chlorination or another method that has demonstrated comparable results to chlorination.
- For R-3 recycled water, wastewater must be oxidized (Hawai'i State DOH, 2016b). The limits specified in the table are set based on system size. Since R-3 is neither filtered nor disinfected, there are no requirements for filtration, turbidity or disinfection.
Additional context and definitions
Hawai'i defines recycled water as “treated wastewater that by design is intended or used for a beneficial purpose” (Haw. Code R. § 11-62). Food crop” is defined as “any crop intended for human consumption” (Hawai'i State DOH, 2016a).
Hawai'i recommends that human contact with recycled water should be avoided as much as possible by, for example, irrigating from 11 pm to 3 am or other times when public contact with recycled water is minimal (Hawai'i State DOH, 2016a). Components of recycled water systems such as piping, valves, valve covers, etc., must be identified to distinguish them from potable water systems, preferably by being purple in color (Pantone 512 or equal). Where color identification is not feasible, components should be labeled with the words “Recycled Water,” “Recycled Water – Do Not Drink,” or similar (Haw. Code R. § 11-62). Signage must also be posted with both written and pictorial warnings that indicate the quality of the recycled water, its end use and an appropriate warning against human consumption and/or what to do if contact occurs. Signs must be posted in clear view of the public along the border of and within the use area with a recommended maximum spacing of 250 feet between signs.
Water reuse for agriculture specifications
Summary of Hawai'i’s Water Reuse for Agriculture Specifications
| Recycled Water Class/Category | Source Water Type | Water Quality Parameter | Specification | Sampling/Monitoring Requirements (Frequency of monitoring; site/ location of sample; quantification methods)* |
|---|---|---|---|---|
|
R-1 recycled water (All agricultural irrigation via spray, surface drip or subsurface drip irrigation; Agricultural cleaning) |
Municipal wastewater |
5-day biochemical oxygen demand (BOD5) |
≤5 mg/L (recommended target) ≤30 mg/L (monthly composite average for large non-pond systems) ≤60 mg/L (single sample maximum, all systems) |
Weekly sampling for systems with average daily flow of ≥100,000 gallons/day; monthly sampling for <100,000 gallons/day |
|
Total suspended solids (TSS) |
||||
|
Turbidity (for media filtration) |
≤2 NTU (24-hour average) ≤5 NTU (exception maximum of 72 minutes within a 24-hour period) ≤10 NTU (single sample maximum) |
Continuous monitoring both prior to filtration and after filtration but before disinfection |
||
|
Turbidity (for membrane filtration) |
≤0.2 NTU (exception maximum of 72 minutes within a 24-hour period) ≤0.5 NTU (single sample maximum) |
|||
|
Turbidity (for reverse osmosis) |
||||
|
Total chlorine residuala (CT) |
≤450 mg-min/L at all times ≥90 minutes (modal contact time) Equivalent to 5 mg/L residual chlorine at all times |
Continuous monitoring |
||
|
UV disinfectionb (for media filtration) |
≥100 mJ/cm2 (design dose under maximum daily flow) ≥55% (transmittance at 254 nm) |
Not specified |
||
|
UV disinfectionb (for membrane filtration) |
≥80 mJ/cm2 (design dose under maximum daily flow) ≥65% (transmittance at 254 nm) |
|||
|
UV disinfectionb (for reverse osmosis) |
≥50 mJ/cm2 (design dose under maximum daily flow) ≥90% (transmittance at 254 nm) |
|||
|
F-specific bacteriophage MS2 |
99.999% removal (PFU) |
Not specified |
||
|
Polio virus |
99.999% removal |
Not specified |
||
|
Another virus at least as resistant to disinfection as the polio virus |
99.999% removal |
Not specified |
||
|
Fecal coliforms |
≤2.2 per 100 mL (7-day median) ≤23 per 100 mL (30-day single sample maximum) ≤200 per 100 mL (single sample maximum) |
Daily; may be reduced to weekly under certain conditions |
||
|
R-2 recycled water (Surface drip or subsurface drip irrigation for sod farms and ornamental plants for commercial use) |
Municipal wastewater |
BOD5 |
≤10 mg/L (recommended target) ≤30 mg/L (monthly composite average for large non-pond systems) ≤60 mg/L (single sample maximum, all systems) |
Weekly sampling for systems with average daily flow of ≥100,000 gallons/day; monthly sampling for <100,000 gallons/day |
|
TSS |
||||
|
Chlorinea,c |
≥15 min (theoretical contact time) ≥10 min (actual modal contact time) 0.5 mg/L (residual) 2 mg/L (residual capacity) |
Continuous monitoring |
||
|
Fecal coliform density |
≤23 per 100 mL (7-day median) ≤200 per 100 mL (30-day single sample maximum) |
Daily; may be reduced to weekly under certain conditions |
||
|
R-3 recycled water (Drip or subsurface drip irrigation in areas with limited public access for non-edible vegetation; fodder, fiber and seed crops not consumed by humans; and timber and trees not bearing food crops) |
Municipal wastewater |
BOD5 |
≤30 mg/L (monthly composite average for large non-pond systems) ≤60 mg/L (single sample maximum, all systems) |
Weekly sampling for systems with average daily flow of ≥100,000 gallons/day; monthly sampling for <100,000 gallons/day |
|
TSS |
||||
|
Nitrogen |
Not specified |
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|
Phosphorus |
Not specified |
Source= Haw. Code R. § 11-62; Hawai'i State DOH (2016a)
* 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 Where chlorination is used for disinfection.
b Where UV is used for disinfection. The minimal acceptable design requirements and commissioning of new UV disinfection systems shall comply with the latest Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse prepared by the National Water Research Institute and Water Research Foundation that has been accepted for use by the Hawai'i Department of Health; a UV system that is Title 22 certified by California is also acceptable.
c When an alternate disinfection process is used, the applicant must show to the satisfaction of the Department of Health that the process results are comparable to those achieved by chlorination.
Upcoming state law or policy
No upcoming regulations pertaining to water reuse for agriculture were found for Hawai'i.
References
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
Food Safety Modernization Act (FSMA), 124 Stat. 3885.
Hawai'i State Department of Health (DOH) Wastewater Branch. 2016a. Reuse Guidelines Volume 1: Recycled Water Facilities.
Hawai'i State DOH Wastewater Branch. 2016b. Reuse Guidelines Volume 2: Recycled Water Projects.
Wastewater Systems, Haw. Code R. § 11-62.
Water Recycling Criteria, Cal. Code Regs. tit. 22.
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