Oxidation ditches: wastewater treatment plants in Iowa
17 plants · 2% of the state · 18 MGD combined
Klarifi identifies 17 publicly owned wastewater treatment plants with oxidation ditches in Iowa, 2% of the 747 plants in the state (18 MGD combined). The largest is Coralville WWTP in Coralville at 2.98 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 | Coralville WWTP | Coralville | 2.98 | IA0020788 | Sep 2031 | 1 |
| 2 | Storm Lake WWTP | Storm Lake | 2.45 | IA0032484 | Oct 2029 | 3 |
| 3 | Indianola Water Resource Recovery Facility | Indianola | 1.96 | IA0053405 | Aug 2027 | 5 |
| 4 | Eagle Grove, City Of STP | Eagle Grove | 1.93 | IA0034380 | Feb 2030 | 11 |
| 5 | Waverly WWTP | Waverly | 1.42 | IA0033197 | Aug 2031 | 1 |
| 6 | Nevada City Of WWTP | Nevada | 1.37 | IA0053648 | Apr 2030 | 2 |
| 7 | Grinnell, City Of STP | Grinnell | 1.35 | IA0031186 | Nov 2029 | 0 |
| 8 | Dewitt WWTP | Dewitt | 0.82 | IA0035271 | Sep 2029 | 6 |
| 9 | Chariton City Of STP | Chariton | 0.67 | IA0028924 | Jul 2029 | 16 |
| 10 | Huxley City Of STP | Huxley | 0.61 | IA0083518 | Feb 2027 | 2 |
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 October 26, 2026.
Wastewater terms: Oxidation ditch · Activated sludge · Biological nutrient removal · MGD · Lift station · all terms