Activated sludge and clarifiers: wastewater treatment plants in Montana
13 plants · 12% of the state · 49 MGD reported by 11 plants
Klarifi identifies 13 publicly owned wastewater treatment plants with activated sludge and clarifiers in Montana, 12% of the 109 plants in the state (49 MGD reported by 11 plants). The largest is City Of Billings Wastewater Treatment Plant in Billings at 20.32 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Montana
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | City Of Billings Wastewater Treatment Plant | Billings | 20.32 | MTR000459 | Jan 2028 | 7 |
| 2 | City Of Missoula WWTF No Exposure | Missoula | 9.3 | MT0022594 | Apr 2020 | 8 |
| 3 | City Of Bozeman WWTP | Bozeman | 6.55 | MT0022608 | May 2017 | 0 |
| 4 | City Of Kalispell WWTP | Kalispell | 3.96 | MT0021938 | Jul 2020 | 11 |
| 5 | City Of Helena WWTP | Helena | 3.01 | MT0022641 | Sep 2017 | 33 |
| 6 | Lewistown WWTP | Lewistown | 1.82 | MT0020044 | Aug 2017 | 32 |
| 7 | Havre WWTF | Havre | 1.68 | MT0022535 | Aug 2026 | 0 |
| 8 | Deer Lodge WWTP | Deer Lodge | 1.13 | MT0022616 | Feb 2018 | 3 |
| 9 | Miles City WWTP | Miles City | 1.11 | MT0020001 | Sep 2023 | 3 |
| 10 | Town Of Poplar WTP | Poplar | 0.54 | MT0030597 | Jun 2025 | 174 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Montana
Activated sludge and clarifiers in other states
Activated sludge and clarifiers 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: Activated sludge · Biological nutrient removal · Equalization tank · Tertiary treatment · Significant industrial user · all terms