How many wastewater treatment plants are there in Montana?

Klarifi tracks 102 publicly owned wastewater treatment plants in Montana with a combined average flow of 60 million gallons per day, serving about 412,669 residents. 8 of them treat more than 1 MGD and 1 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 20.31 MGD.

What treatment technologies are common in Montana?

74 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 27 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

102 facilities · 60 MGD combined flow

Klarifi tracks 102 publicly owned wastewater treatment plants in Montana with a combined average flow of 60 MGD, serving about 412,669 residents. 8 plants treat more than 1 MGD and 1 more than 10 MGD; 74 use lagoon systems and 12 have digesters or biogas infrastructure. The largest is City Of Billings Wastewater Treatment Plant in Billings at 20.31 MGD. 11 NPDES permits expire this year and 27 next year.

Every plant below links to a profile with average and design flow, treatment technology, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city.

102 plant locations in Montana; dot size follows average flow.

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 →27 permits expiring in 2027 →5 permits expiring in 2028 →Find plants near you on the map →

Largest wastewater treatment plants in Montana

The 25 largest publicly owned wastewater treatment plants in Montana by average flow, with NPDES permit, expiry, treatment technology and three-year violation count. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Expires	Technology	Violations (3y)
City Of Billings Wastewater Treatment Plant	Billings	20.31	—	MTR000459	Jan 2028	Clarifiers, Uncovered lagoons, Biogas silos	7
City Of Missoula WWTF No Exposure	Missoula	7.52	12	MT0022594	Apr 2020	Clarifiers, Biogas silos	7
City Of Bozeman WWTP	Bozeman	7.35	—	MT0022608	May 2017	Clarifiers, Biogas silos	0
City Of Kalispell WWTP	Kalispell	3.21	—	MT0021938	Jul 2020	Clarifiers, Biogas silos	11
City Of Helena WWTP	Helena	3.14	—	MT0022641	Sep 2017	Clarifiers, Biogas silos	37
Lewistown WWTP	Lewistown	2.38	2.5	MT0020044	Aug 2017	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos	32
Havre WWTF	Havre	1.64	—	MT0022535	Aug 2026	Clarifiers	0
Miles City WWTP	Miles City	1.11	1.98	MT0020001	Sep 2023	Clarifiers, Carrousels / oxidation ditches	3
City Of Glendive Water Resource & Recovery Facility	Glendive	0.84	1.6	MT0021628	May 2027	—	3
City Of Hamilton Wastewater Treatment Plant	Hamilton	0.79	—	MT0020028	Dec 2026	Carrousels / oxidation ditches	0
Deer Lodge WWTP	Deer Lodge	0.72	—	MT0022616	Feb 2018	Clarifiers, Uncovered lagoons	3
Water Reclamation Facility	Livingston	0.69	2.18	MT0020435	Oct 2021	Aerated lagoons, Biogas balloons	0
City Of Glasgow Parks Maintenance Bldg	Glasgow	0.66	—	MT0021211	Nov 2026	—	21
Anaconda-Deer Lodge County Wastewater Holding Ponds And Ip Beds Facility	Anaconda	0.66	—	MTX000231	May 2024	Uncovered lagoons	0
Town Of Poplar WTP	Poplar	0.59	0.6	MT0030597	Jun 2025	Clarifiers, Carrousels / oxidation ditches	176
Red Lodge WWTF	Red Lodge	0.57	1.2	MT0020478	Apr 2027	Aerated lagoons	3
City Of Shelby Wastewater Lagoons	Shelby	0.53	—	MT0031488	Feb 2025	—	20
City Of Polson WWTP	Polson	0.5	0.65	MT0020559	Aug 2024	—	0
City Of Belgrade- Belgrade Wastewater Treatment Plant	Belgrade	0.5	—	MTX000116	Sep 2023	Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos	30
Northern Cheyenne Utility Commission Wastewater Treatment Plant	Lame Deer	0.47	0.4	MT0029360	Jun 2029	—	737
Columbia Falls WWTP	Columbia Falls	0.43	—	MT0020036	May 2030	—	0
Manhattan WWTF	Manhattan	0.32	0.37	MT0021857	Aug 2015	—	20
Bigfork County Water And Sewer	Bigfork	0.32	0.69	MT0020397	Apr 2023	—	1
Three Forks WWTF	Three Forks	0.31	0.61	MT0020401	Apr 2027	Covered lagoons, Uncovered lagoons	5
City Of Laurel, Water Treatment Plant	Laurel	0.29	—	MT0030261	Oct 2027	—	0

The 50 largest plants in Montana →Montana capital improvement plans →

Montana plants by treatment technology

Lagoon systems (74)Activated sludge and clarifiers (13)Anaerobic digesters and biogas (12)Oxidation ditches (8)

All 102 plants in Montana

Facility	City	Flow (MGD)
City Of Billings Wastewater Treatment Plant	Billings	20.31
City Of Missoula WWTF No Exposure	Missoula	7.52
City Of Bozeman WWTP	Bozeman	7.35
City Of Kalispell WWTP	Kalispell	3.21
City Of Helena WWTP	Helena	3.14
Lewistown WWTP	Lewistown	2.38
Havre WWTF	Havre	1.64
Miles City WWTP	Miles City	1.11
City Of Glendive Water Resource & Recovery Facility	Glendive	0.84
City Of Hamilton Wastewater Treatment Plant	Hamilton	0.79
Deer Lodge WWTP	Deer Lodge	0.72
Water Reclamation Facility	Livingston	0.69
City Of Glasgow Parks Maintenance Bldg	Glasgow	0.66
Anaconda-Deer Lodge County Wastewater Holding Ponds And Ip Beds Facility	Anaconda	0.66
Town Of Poplar WTP	Poplar	0.59
Red Lodge WWTF	Red Lodge	0.57
City Of Shelby Wastewater Lagoons	Shelby	0.53
City Of Polson WWTP	Polson	0.5
City Of Belgrade- Belgrade Wastewater Treatment Plant	Belgrade	0.5
Northern Cheyenne Utility Commission Wastewater Treatment Plant	Lame Deer	0.47
Columbia Falls WWTP	Columbia Falls	0.43
Manhattan WWTF	Manhattan	0.32
Bigfork County Water And Sewer	Bigfork	0.32
Three Forks WWTF	Three Forks	0.31
City Of Laurel, Water Treatment Plant	Laurel	0.29
Great Falls WTP	Great Falls	0.27
Choteau Sewage Treatment Ponds	Choteau	0.25
Libby WWTP	Libby	0.23
Stevensville Waste Water Treatment Plant	Stevensville	0.21
Ronan City WWTF	Ronan	0.2
Forsyth WWTP	Forsyth	0.19
City Of Townsend Wastewater Treatment Plant	Townsend	0.19
City Of Bozeman - Lyman Creek Reservoir	Bozeman	0.19
East Helena WWTF	East Helena	0.18
City Of Cut Bank WWTF	Cut Bank	0.17
City Of Conrad WWTF	Conrad	0.16
River Rock Subdivision	Belgrade	0.15
Town Of Columbus - Waste Water Treatment Facility	Columbus	0.14
Ennis WWTP	Ennis	0.13
Gardiner Wastewater Treatment Facility	Gardiner	0.13
Bozeman Water Treatment Plant	Bozeman	0.13
Montana State Hospital Sewage Treatment Lagoons	Warm Springs	0.12
City Of Chinook WTP	Chinook	0.11
Hot Springs, Town Of	Hot Springs	0.1
City Of Troy Wastewater Treatment Facility	Troy	0.1
Park City County Wastewater Treatment Facility	Park City	0.1
Town Of Plains WWTP	Plains	0.1
Town Of Eureka WWTP	Eureka	0.09
City Of Boulder WWTF	Boulder	0.09
Town Of Philipsburg WWTP	Philipsburg	0.07
City Of Harlowton WWTF	Harlowton	0.07
Town Of Culbertson Domestic WWTF	Culbertson	0.06
Joliet WWTP	Joliet	0.06
Chinook WWTP	Chinook	0.06
Sun Prairie Village WWTP	Great Falls	0.05
City Of Thompson Falls WWTF	Thompson Falls	0.05
White Sulphur Springs WWTF	White Sulphur Springs	0.05
St. Ignatius-Southside	St. Ignatius	0.04
Vaughn WWTF	Vaughn	0.03
Superior Wastewater Treatment Facility	Superior	0.03
Alberton WWTP	Alberton	0.02
Yellow Bay WWTP	Polson	0.01
Kootenai Lodge Lake County Water And Sewer Dist	Bigfork	0.0043
Ekalaka WWTF	Ekalaka	0.0019
Wolf Creek WWTF	Wolf Creek	0.0018
Agency Lagoon	Box Elder	—
Azure Lagoon	Box Elder	—
Big Timber	Big Timber	—
Brady County Water Sewer District	Brady	—
Bridger WWTP	Bridger	—
City Of Baker WWTF	Baker	—
City Of Great Falls WWTP	Great Falls	—
Crow Agency Lagoon	Crow Agency	—
Fort Benton WWTP	Fort Benton	—
Highwood WWTP	Highwood	—
Hobson Sewage Treatment Plant	Hobson	—
Lodge Grass, Town Of WWTF	Lodge Grass	—
Lower Dry Fork Lagoon	Box Elder	—
Malta Sewage Treatment Lagoons	Malta	—
Multi-Community Lagoon	Box Elder	—
Stockett Water And Sewer District Domestic Wastewater Treatment Facility	Stockett	—
Sunburst WWTF	Sunburst	—
Sweet Grass WWTF	Sweet Grass	—
Town Of Belt - WWTP	Belt	—
Town Of Broadus WWTF	Broadus	—
Town Of Chester WWTF	Chester	—
Town Of Darby WWTF	Darby	—
Town Of Denton WWTP	Denton	—
Town Of Fairfield WWTP	Fairfield	—
Town Of Fort Peck WWTF	Fort Peck	—
Town Of Geraldine WWTF	Geraldine	—
Town Of Jordan Wastewater Treatmetn Facility	Jordan	—
Town Of Kevin WWTF	Kevin	—
Town Of Lavina WWTF	Lavina	—
Town Of Nashua WWTF	Nashua	—
Town Of Saco	Saco	—
Town Of Terry WWTF	Terry	—
Town Of Valier WWTF	Valier	—
Twin Bridges WWTF	Twin Bridges	—
Willow Creek Wastewater Treatment Plant	Willow Creek	—
Wolf Point, City Of	Wolf Point	—
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 September 11, 2026.

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