Oxidation ditches: wastewater treatment plants in Idaho
12 plants · 13% of the state · 5 MGD reported by 8 plants
Klarifi identifies 12 publicly owned wastewater treatment plants with oxidation ditches in Idaho, 13% of the 94 plants in the state (5 MGD reported by 8 plants). The largest is Rigby WWTP in Rigby at 1.2 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 Idaho
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Rigby WWTP | Rigby | 1.2 | ID0020010 | Dec 2021 | 9 |
| 2 | Payette WWTP | Payette | 1 | ID0020672 | Oct 2019 | 1 |
| 3 | Moscow STP | Moscow | 0.85 | ID0021491 | Jan 2031 | 0 |
| 4 | Heyburn WWTP | Heyburn | 0.71 | ID0020940 | Jan 2007 | 17 |
| 5 | Grangeville WWTP | Grangeville | 0.39 | ID0020036 | Apr 2025 | 3 |
| 6 | Buhl WWTP | Buhl | 0.29 | ID0020664 | Oct 2012 | 2 |
| 7 | Grace WWTP | Grace | 0.08 | ID0023825 | Jun 2027 | 1 |
| 8 | Hansen STP | Hansen | 0.07 | ID0022446 | Oct 2012 | 7 |
| 9 | Fruitland Payette River WWTP | Payette | — | ID0021199 | Oct 2016 | 3 |
| 10 | Greenleaf STP | Greenleaf | — | ID0028304 | Dec 2017 | 1 |
| 11 | Hayden Area Regional Sewer Board WWTP | Hayden | — | ID0026590 | May 2029 | 5 |
| 12 | Rexburg WWTP | Rexburg | — | ID0023817 | Mar 2028 | 41 |
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 Idaho
Oxidation ditches in other states
Oxidation ditches in Idaho: 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.