Lagoon systems: wastewater treatment plants in Iowa
625 plants · 84% of the state · 146 MGD reported by 288 plants
Klarifi identifies 625 publicly owned wastewater treatment plants with lagoon systems in Iowa, 84% of the 747 plants in the state (146 MGD reported by 288 plants). The largest is Water Pollution Control Facility in Cedar Rapids at 39.59 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in Iowa
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Water Pollution Control Facility | Cedar Rapids | 39.59 | IA0042641 | Aug 2030 | 15 |
| 2 | Fort Dodge City Of STP | Fort Dodge | 11.42 | IA0044849 | Dec 2030 | 0 |
| 3 | Iowa City, City Of (south) STP | Iowa City | 8.98 | IA0070866 | Jul 2030 | 11 |
| 4 | Mason WWTP | Mason City | 5.13 | IA0077305 | May 2029 | 6 |
| 5 | Ottumwa City Of STP | Ottumwa | 3.24 | IA0058611 | Feb 2031 | 1 |
| 6 | Storm Lake WWTP | Storm Lake | 2.45 | IA0032484 | Oct 2029 | 3 |
| 7 | West Liberty City Of STP | West Liberty | 2.41 | IA0031691 | Jun 2030 | 18 |
| 8 | City Of Emmetsburg Treatment Plant | Emmetsburg | 2.38 | IA0021580 | Apr 2031 | 80 |
| 9 | North Liberty WWTP | North Liberty | 2.03 | IA0032905 | Apr 2031 | 0 |
| 10 | Eagle Grove, City Of STP | Eagle Grove | 1.93 | IA0034380 | Feb 2030 | 11 |
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
Lagoon systems in other states
Lagoon systems 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: WWTP · POTW · Biosolids · Biological nutrient removal · Tertiary treatment · all terms