Oxidation ditches: wastewater treatment plants in Montana
8 plants · 8% of the state · 6 MGD combined
Klarifi identifies 8 publicly owned wastewater treatment plants with oxidation ditches in Montana, 8% of the 102 plants in the state (6 MGD combined). The largest is Lewistown WWTP in Lewistown at 2.38 MGD.
Oxidation ditches are ring-shaped activated sludge reactors with long retention times, common at plants between 0.5 and 10 MGD. They are recognisable from the air by their looped channels and rely on surface aerators or brush rotors, which are frequent replacement and energy-efficiency projects.
The largest oxidation ditch plants in Montana
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Lewistown WWTP | Lewistown | 2.38 | MT0020044 | Aug 2017 | 32 |
| 2 | Miles City WWTP | Miles City | 1.11 | MT0020001 | Sep 2023 | 3 |
| 3 | City Of Hamilton Wastewater Treatment Plant | Hamilton | 0.79 | MT0020028 | Dec 2026 | 0 |
| 4 | Town Of Poplar WTP | Poplar | 0.59 | MT0030597 | Jun 2025 | 176 |
| 5 | City Of Belgrade- Belgrade Wastewater Treatment Plant | Belgrade | 0.5 | MTX000116 | Sep 2023 | 30 |
| 6 | Choteau Sewage Treatment Ponds | Choteau | 0.25 | MT0020052 | Aug 2026 | 3 |
| 7 | Libby WWTP | Libby | 0.23 | MTR000752 | Jan 2028 | 34 |
| 8 | Chinook WWTP | Chinook | 0.06 | MT0020125 | Dec 2025 | 0 |
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
Oxidation ditches in other states
Oxidation ditches 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.