How many wastewater treatment plants are there in Montana?

Klarifi tracks 109 publicly owned wastewater treatment plants in Montana with a combined average flow of 101 million gallons per day, serving about 415,805 residents. 12 of them treat more than 1 MGD and 3 more than 10 MGD.

What is the largest wastewater treatment plant in Montana?

City Of Billings Wastewater Treatment Plant in Billings is the largest plant in Montana by average flow, treating about 20.32 MGD.

What treatment technologies are common in Montana?

72 of Montana's plants use lagoon systems and 12 have biogas or anaerobic digestion infrastructure, based on Klarifi's aerial imagery review.

How many NPDES permits in Montana are up for renewal?

11 permits held by Montana plants expire in 2026 and 30 in 2027. Renewals typically bring new limits and trigger upgrade projects.

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Wastewater treatment plants in Montana

Name: Wastewater treatment plants in Montana
Creator: Klarifi
License: https://klarifi.io/terms-of-service

109 facilities · 101 MGD combined flow

Klarifi tracks 109 publicly owned wastewater treatment plants in Montana with a combined average flow of 101 MGD, serving about 415,805 residents. 12 plants treat more than 1 MGD and 3 more than 10 MGD; 72 use lagoon systems and 12 have digesters or biogas infrastructure. The largest is City Of Billings Wastewater Treatment Plant in Billings at 20.32 MGD. 11 NPDES permits expire this year and 30 next year.

Every plant below links to a profile with average and design flow, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city. Treatment technology and verified contacts are shown with a free Klarifi account.

109 plant locations in Montana; dot size follows average flow. Boundaries: U.S. Census Bureau.

NPDES permits and renewals in Montana

Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.

All NPDES permits in Montana →11 permits expiring in 2026 →30 permits expiring in 2027 →5 permits expiring in 2028 →Find plants near you on the map →

Largest wastewater treatment plants in Montana

The 10 largest publicly owned wastewater treatment plants in Montana by average flow, with NPDES permit, expiry and three-year violation count. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Expires	Violations (3y)
City Of Billings Wastewater Treatment Plant	Billings	20.32	—	MTR000459	Jan 2028	7
Town Of Lavina WWTF	Lavina	18.51	—	MTG580013	Dec 2027	1
Two Medicine Water Co.	Browning	17.08	—	MTDW0003I	Jun 2024	0
City Of Missoula WWTF No Exposure	Missoula	9.3	12	MT0022594	Apr 2020	8
City Of Bozeman WWTP	Bozeman	6.55	—	MT0022608	May 2017	0
City Of Kalispell WWTP	Kalispell	3.96	—	MT0021938	Jul 2020	11
City Of Helena WWTP	Helena	3.01	—	MT0022641	Sep 2017	33
Lewistown WWTP	Lewistown	1.82	2.5	MT0020044	Aug 2017	32
Havre WWTF	Havre	1.68	—	MT0022535	Aug 2026	0
Deer Lodge WWTP	Deer Lodge	1.13	—	MT0022616	Feb 2018	3

Treatment technology for each plant is shown with a free Klarifi account. Create one →

The 50 largest plants in Montana →EPA enforcement actions in Montana →Montana capital improvement plans →

Montana plants by treatment technology

Lagoon systems (73)Activated sludge and clarifiers (13)Anaerobic digesters and biogas (12)Oxidation ditches (8)

All 109 plants in Montana

Facility	City	Flow (MGD)
City Of Billings Wastewater Treatment Plant	Billings	20.32
Town Of Lavina WWTF	Lavina	18.51
Two Medicine Water Co.	Browning	17.08
City Of Missoula WWTF No Exposure	Missoula	9.3
City Of Bozeman WWTP	Bozeman	6.55
City Of Kalispell WWTP	Kalispell	3.96
City Of Helena WWTP	Helena	3.01
Lewistown WWTP	Lewistown	1.82
Havre WWTF	Havre	1.68
Deer Lodge WWTP	Deer Lodge	1.13
Miles City WWTP	Miles City	1.11
Wolf Point, City Of	Wolf Point	1.08
City Of Polson WWTP	Polson	0.86
City Of Glendive Water Resource & Recovery Facility	Glendive	0.85
Town Of Belt - WWTP	Belt	0.82
Water Reclamation Facility	Livingston	0.69
City Of Hamilton Wastewater Treatment Plant	Hamilton	0.67
City Of Glasgow Parks Maintenance Bldg	Glasgow	0.61
City Of Shelby Wastewater Lagoons	Shelby	0.57
Town Of Poplar WTP	Poplar	0.54
Northern Cheyenne Utility Commission Wastewater Treatment Plant	Lame Deer	0.48
Stevensville Waste Water Treatment Plant	Stevensville	0.47
Choteau Sewage Treatment Ponds	Choteau	0.47
Anaconda-Deer Lodge County Wastewater Holding Ponds And Ip Beds Facility	Anaconda	0.44
Ennis WWTP	Ennis	0.44
Three Forks WWTF	Three Forks	0.44
Hot Springs, Town Of	Hot Springs	0.43
Columbia Falls WWTP	Columbia Falls	0.41
Bigfork County Water And Sewer	Bigfork	0.37
City Of Belgrade- Belgrade Wastewater Treatment Plant	Belgrade	0.36
Libby WWTP	Libby	0.33
Great Falls WTP	Great Falls	0.33
City Of Bozeman - Lyman Creek Reservoir	Bozeman	0.3
City Of Laurel, Water Treatment Plant	Laurel	0.29
Manhattan WWTF	Manhattan	0.29
Town Of Terry WWTF	Terry	0.26
City Of Townsend Wastewater Treatment Plant	Townsend	0.23
Forsyth WWTP	Forsyth	0.23
City Of Plentywood	Plentywood	0.22
East Helena WWTF	East Helena	0.18
City Of Conrad WWTF	Conrad	0.17
Big Timber	Big Timber	0.16
Town Of Fairfield WWTP	Fairfield	0.16
River Rock Subdivision	Belgrade	0.16
Town Of Columbus - Waste Water Treatment Facility	Columbus	0.15
City Of Troy Wastewater Treatment Facility	Troy	0.15
Town Of Drummond WWTP	Drummond	0.13
Montana State Hospital Sewage Treatment Lagoons	Warm Springs	0.13
Town Of Broadus WWTF	Broadus	0.11
Town Of Eureka WWTP	Eureka	0.11
Gardiner Wastewater Treatment Facility	Gardiner	0.1
Town Of Philipsburg WWTP	Philipsburg	0.1
City Of Chinook WTP	Chinook	0.09
Bozeman Water Treatment Plant	Bozeman	0.09
City Of Boulder WWTF	Boulder	0.08
City Of Harlowton WWTF	Harlowton	0.08
Town Of Plains WWTP	Plains	0.08
Park City County Wastewater Treatment Facility	Park City	0.08
Winnett WWTF	Winnett	0.07
Fort Benton WWTP	Fort Benton	0.06
Sun Prairie Village WWTP	Great Falls	0.05
Superior Wastewater Treatment Facility	Superior	0.05
Ekalaka WWTF	Ekalaka	0.05
Joliet WWTP	Joliet	0.05
City Of Thompson Falls WWTF	Thompson Falls	0.05
White Sulphur Springs WWTF	White Sulphur Springs	0.05
Chinook WWTP	Chinook	0.05
Town Of Darby WWTF	Darby	0.05
Highwood WWTP	Highwood	0.04
Fromberg Wastewater Treatment Facility	Fromberg	0.04
Alberton WWTP	Alberton	0.04
Sunburst WWTF	Sunburst	0.04
Bridger WWTP	Bridger	0.04
Town Of Culbertson Domestic WWTF	Culbertson	0.04
Vaughn WWTF	Vaughn	0.03
St. Ignatius-Southside	St. Ignatius	0.02
Consolidated Charlo-Lake County Water&sewer Dist	Charlo	0.02
Stockett Water And Sewer District Domestic Wastewater Treatment Facility	Stockett	0.02
Town Of Jordan Wastewater Treatmetn Facility	Jordan	0.02
Town Of Valier WWTF	Valier	0.02
Lodge Grass, Town Of WWTF	Lodge Grass	0.0089
Yellow Bay WWTP	Polson	0.0086
Town Of Kevin WWTF	Kevin	0.0083
Kootenai Lodge Lake County Water And Sewer Dist	Bigfork	0.007
Wolf Creek WWTF	Wolf Creek	0.003
Agency Lagoon	Box Elder	—
Azure Lagoon	Box Elder	—
Brady County Water Sewer District	Brady	—
City Of Baker WWTF	Baker	—
City Of Cut Bank WWTF	Cut Bank	—
City Of Great Falls WWTP	Great Falls	—
Crow Agency Lagoon	Crow Agency	—
Hobson Sewage Treatment Plant	Hobson	—
Lower Dry Fork Lagoon	Box Elder	—
Malta Sewage Treatment Lagoons	Malta	—
Multi-Community Lagoon	Box Elder	—
Red Lodge WWTF	Red Lodge	—
Ronan City WWTF	Ronan	—
Sweet Grass WWTF	Sweet Grass	—
Town Of Chester WWTF	Chester	—
Town Of Denton WWTP	Denton	—
Town Of Fort Peck WWTF	Fort Peck	—
Town Of Geraldine WWTF	Geraldine	—
Town Of Nashua WWTF	Nashua	—
Town Of Saco	Saco	—
Twin Bridges WWTF	Twin Bridges	—
Willow Creek Wastewater Treatment Plant	Willow Creek	—
Winifred Domestic WWTF	Winifred	—
Woodcock Home Addition (e)	Pablo	—

Wastewater treatment in Montana: questions

Sources and methodology

Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.

Data refreshed October 26, 2026.

Wastewater terms: WWTP · POTW · MGD · NPDES permit · Oxidation ditch · Anaerobic digester · all terms

Cite this page

Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.

Klarifi. “Wastewater treatment plants in Montana.” Updated October 26, 2026. https://klarifi.io/facilities/montana

Need a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.

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