Summary of Montana's Water Reuse Guideline or Regulation for Centralized Non-potable 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.
On this page:
- Technical basis
- Applications of centralized non-potable reuse approved for use in Montana
- Water reuse category/type
- Additional context and definitions
- Centralized non-potable reuse 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 Montana, centralized non-potable reuse The use of recycled water for centralized non-potable reuse where the water does not derive from the same site where it is to be reused. Can include, but is not limited to, toilet flushing, dust control, soil compaction, fire protection, commercial laundries, vehicle washing, street cleaning, snowmaking, and other similar uses. Excludes on-site non-potable water reuse and the use of recycled water for agriculture or landscaping. applications include toilet and urinal flushing, firefighting and zoo operations, among others. 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
Montana approves the use of reclaimed water for centralized non-potable reuse applications including, but not limited to, toilet and urinal flushing, decorative fountains, firefighting, snowmaking, street cleaning and dust control (Circular DEQ 2). 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 state water quality standards. Treatment requirements and performance standards are applied for the removal of pathogen and chemical contaminants for centralized non-potable reuse applications to ensure “an adequate demonstration of public health and environmental protection” (Circular DEQ 2). The technical basis for the removal of pathogen and chemical contaminant is not explicitly specified.
Applications of centralized non-potable reuse approved for use in Montana
Circular DEQ 2 defines the following approved centralized non-potable uses:
- Toilet and urinal flushing (Class A)
- Decorative fountains discharged to the sewer (Class A) and to groundwater (Class A-1)
- Firefighting
- Fire protection systems like hydrants or sprinkler systems in buildings (Class A-1 and A)
- Dumping from aircraft (Class C)
- Snowmaking
- Unrestricted access, ex. ski slopes (Class A-1)
- Restricted access, ex. designed for discharge to groundwater (Class B-1)
- Zoo operations and animal shelter washdown water discharged to sewer (Class B)
- Washing aggregate and concrete batching (Class C)
- Jetting and flushing of sanitary sewers (Class C)
- Street cleaning and washing operations
- Sidewalks and parking lot washing, spray (Class B-1)
- Street sweeping, brush dampening (Class C)
- Dust control and soil compaction/consolidation (Class C)
Water reuse category/type
The various classes of treatment are defined by their respective treatment requirements and applicable performance standards, differentiated by the degree of additional treatment provided following secondary treatment. The respective treatment requirements are briefly summarized for centralized non-potable reuse applications:
- For Class A-1 and Class A reclaimed wastewater, the treatment requirements are secondary treatment, oxidation, coagulation, filtration and disinfection to achieve a BOD and TSS of ≤10 mg/L and a turbidity of ≤2 NTU (average) and ≤5 NTU (single sample maximum). Class A-1 reclaimed wastewater has an additional total nitrogen requirement of ≤5 mg/L.
- For Class B-1 and Class B reclaimed wastewater, the treatment requirements are secondary treatment, oxidation, settling and disinfection to achieve total coliform organisms ≤2.2 CFU/100 mL (7-day median) and ≤23 CFU/100 mL (single sample maximum). Class B-1 reclaimed wastewater has an additional total nitrogen requirement of ≤5 mg/L.
- For Class C reclaimed wastewater, the treatment requirements are secondary treatment, oxidation, settling and disinfection to achieve total coliform organisms ≤23 CFU/100 mL (7-day median) and ≤240 CFU/100 mL (single sample maximum).
Additional context and definitions
In Montana, reclaimed wastewater is defined as “wastewater treated by a public sewage system for reuse for private, public, or commercial purposes” (Circular DEQ 2).
Montana requires that conveyance systems for the delivery of municipal reclaimed wastewater be easily identifiable; the use of purple piping or purple striped piping is encouraged (MT DEQ 2018). Reclaimed water plumbing must not be cross connected to any potable water supply within the structure. Areas of reclaimed wastewater use must have signs posted at conspicuous public access points that read “Reclaimed wastewater – Do Not Drink” or an approved equivalent warning.
Centralized non-potable reuse specifications
Summary of Montana's Centralized Non-potable Reuse Specifications
| Recycled Water Class/Category | Source Water Type | Water Quality Parameter | Specification | Sampling/Monitoring Requirements (Frequency of monitoring; site/ location of sample; quantification methods)* |
|---|---|---|---|---|
|
Class A-1 (decorative fountains discharged to groundwater, fire protection systems in buildings, unrestricted access snowmaking) |
Municipal wastewater |
Must meet the treatment requirements for Class A water and the additional total nitrogen specification. |
||
|
Total nitrogen |
≤5 mg/L |
Biweekly analysis |
||
|
Class A (toilet and urinal flushing, decorative fountains discharged to the sewer, fire protection systems in buildings) |
Municipal wastewater |
Must meet the total coliform requirements for Class B water and the additional treatment requirements. |
||
|
5-day biochemical oxygen demand (BOD5) |
≤10 mg/L |
Measured following treatment |
||
|
Total suspended solids (TSS) |
≤10 mg/L |
|||
|
Turbidity |
≤2 NTU (average) ≤5 NTU (single sample maximum) |
Continuous monitoring |
||
|
Total nitrogen |
None, monitor only |
Monthly analysis |
||
|
Class B-1 (restricted access snowmaking, sidewalk and parking lot cleaning) |
Municipal wastewater |
Must meet the total coliform requirements for Class B water and the additional total nitrogen specification. |
||
|
Total nitrogen |
≤5 mg/L |
Biweekly analysis |
||
|
Class B (zoo operations, animal shelter washdown water) |
Municipal wastewater |
Total coliform |
≤2.2 CFU/100 mL (7-day median) ≤23 CFU/100 mL (single sample maximum) |
Weekly analysis |
|
Total nitrogen |
None, monitor only |
Monthly analysis |
||
|
Class C (aircraft firefighting, washing aggregate, concrete batching, flushing sanitary sewers, street sweeping, brush dampening, dust control, soil compaction) |
Municipal wastewater |
Total coliform |
≤23 CFU/100 mL (7-day median) ≤240 CFU/100 mL (single sample maximum) |
Monthly analysis |
|
Total nitrogen |
None, monitor only |
|||
Source = Circular DEQ 2
* 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.
Upcoming state law or policy
No upcoming regulations pertaining to centralized non-potable reuse were found for Montana.
References:
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
Design Standards for Public Sewage Systems, Circular DEQ 2.
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.