Oxidation ditches: wastewater treatment plants in Iowa
17 plants · 3% of the state · no reported flow
Klarifi identifies 17 publicly owned wastewater treatment plants with oxidation ditches in Iowa, 3% of the 678 plants in the state (no reported flow). The largest is Mitchell County WW Pretreatment Plant in Osage at 0.03 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 Iowa
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Mitchell County WW Pretreatment Plant | Osage | 0.03 | MO0030821 | Jun 2026 | 111 |
| 2 | Asbury City Of STP | Asbury | — | IA0069922 | Oct 2029 | 1 |
| 3 | Chariton City Of STP | Chariton | — | IA0028924 | Jul 2029 | 15 |
| 4 | Coralville WWTP | Coralville | — | IA0020788 | Mar 2026 | 1 |
| 5 | Dewitt WWTP | Dewitt | — | IA0035271 | Sep 2029 | 5 |
| 6 | Dike WWTP | Dike | — | IA0023311 | Oct 2030 | 3 |
| 7 | Dyersville WWTP | Dyersville | — | IA0023345 | Jan 2031 | 12 |
| 8 | Eagle Grove, City Of STP | Eagle Grove | — | IA0034380 | Feb 2030 | 11 |
| 9 | Grinnell, City Of STP | Grinnell | — | IA0031186 | Nov 2029 | 0 |
| 10 | Hartley WWTP | Hartley | — | IA0036480 | Nov 2029 | 7 |
| 11 | Huxley City Of STP | Huxley | — | IA0083518 | Feb 2027 | 2 |
| 12 | Indianola Water Resource Recovery Facility | Indianola | — | IA0053405 | Aug 2027 | 5 |
| 13 | Nevada City Of WWTP | Nevada | — | IA0053648 | Apr 2030 | 2 |
| 14 | Osage City Of STP | Osage | — | IA0032956 | Jan 2030 | 50 |
| 15 | Storm Lake WWTP | Storm Lake | — | IA0032484 | Oct 2029 | 3 |
| 16 | Sumner City Of STP | Sumner | — | IA0033766 | Dec 2027 | 1 |
| 17 | Waverly WWTP | Waverly | — | IA0033197 | Aug 2031 | 1 |
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 Iowa
Oxidation ditches in other states
Oxidation ditches in Iowa: 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.