The 50 largest wastewater treatment plants in Iowa
Ranked by average flow · 198 MGD combined · 74% of the state's reported flow
Water Pollution Control Facility in Cedar Rapids is the largest publicly owned wastewater treatment plant in Iowa by reported average flow, treating about 39.59 million gallons per day. The 50 plants below treat 198 MGD between them, 74% of the flow reported by all 747 plants in the state, and serve about 990,478 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| 1 | Water Pollution Control Facility | Cedar Rapids | 39.59 | 165,738 | IA0042641 | Aug 2030 | 15 |
| 2 | Davenport Wastewater Treatment Plant | Davenport | 25.36 | 132,801 | IA0043052 | Jun 2026 | 0 |
| 3 | City Of Sioux City STP | Sioux City | 14.01 | 94,220 | IA0043095 | Jan 2031 | 10 |
| 4 | Fort Dodge City Of STP | Fort Dodge | 11.42 | 27,064 | IA0044849 | Dec 2030 | 0 |
| 5 | Iowa City, City Of (south) STP | Iowa City | 8.98 | 22,457 | IA0070866 | Jul 2030 | 11 |
| 6 | Council Bluffs City Of STP | Council Bluffs | 8.21 | 56,770 | IA0036641 | Aug 2031 | 0 |
| 7 | Clinton WWTP | Clinton | 6.52 | 30,521 | IA0035947 | Jun 2031 | 12 |
| 8 | Burlington, City Of (wwtp) | Burlington | 5.79 | 28,438 | IA0043079 | Jan 2027 | 4 |
| 9 | Mason WWTP | Mason City | 5.13 | 30,353 | IA0077305 | May 2029 | 6 |
| 10 | Cedar Falls City Of STP | Cedar Falls | 4.83 | 35,848 | IA0036633 | Dec 2029 | 0 |
| 11 | City Of Muscatine Water & Resource Recovery Facility | Muscatine | 3.89 | 22,886 | IA0023434 | Mar 2030 | 16 |
| 12 | Ottumwa City Of STP | Ottumwa | 3.24 | 25,595 | IA0058611 | Feb 2031 | 1 |
| 13 | City Of Boone Water Pollution Control | Boone | 3.05 | 13,382 | IA0058076 | Nov 2029 | 3 |
| 14 | Coralville WWTP | Coralville | 2.98 | 20,178 | IA0020788 | Sep 2031 | 1 |
| 15 | Iowa Great Lakes Sanitary District WWTP | Milford | 2.5 | 27,201 | IA0059765 | Aug 2026 | 15 |
| 16 | Storm Lake WWTP | Storm Lake | 2.45 | 11,156 | IA0032484 | Oct 2029 | 3 |
| 17 | Newton City Of STP | Newton | 2.43 | 16,283 | IA0027723 | Apr 2031 | 3 |
| 18 | West Liberty City Of STP | West Liberty | 2.41 | 3,858 | IA0031691 | Jun 2030 | 18 |
| 19 | City Of Emmetsburg Treatment Plant | Emmetsburg | 2.38 | 4,118 | IA0021580 | Apr 2031 | 80 |
| 20 | City Of Pella | Pella | 2.36 | 10,828 | IA0043869 | Mar 2027 | 0 |
| 21 | North Liberty WWTP | North Liberty | 2.03 | 14,223 | IA0032905 | Apr 2031 | 0 |
| 22 | Indianola Water Resource Recovery Facility | Indianola | 1.96 | — | IA0053405 | Aug 2027 | 5 |
| 23 | Eagle Grove, City Of STP | Eagle Grove | 1.93 | 3,880 | IA0034380 | Feb 2030 | 11 |
| 24 | Spencer, City Of | Spencer | 1.75 | 11,829 | IA0021059 | Feb 2024 | 74 |
| 25 | Fredricksburg WWTP | Fredericksburg | 1.7 | 973 | IA0028991 | Jan 2008 | 0 |
| 26 | Keokuk City Of STP | Keokuk | 1.7 | 13,014 | IA0042609 | Mar 2030 | 42 |
| 27 | Osceola WWTP South | Osceola | 1.68 | 5,152 | IA0041815 | Oct 2029 | 159 |
| 28 | Fort Madison City Of STP | Fort Madison | 1.65 | 11,673 | IA0027219 | Dec 2029 | 6 |
| 29 | Washington City Of STP | Washington | 1.65 | 7,352 | IA0032433 | Sep 2031 | 6 |
| 30 | Waverly WWTP | Waverly | 1.42 | 9,369 | IA0033197 | Aug 2031 | 1 |
| 31 | Oelwein WWTP | Oelwein | 1.4 | 7,037 | IA0032344 | May 2026 | 16 |
| 32 | Knoxville City Of STP | Knoxville | 1.39 | 8,080 | IA0035866 | Jul 2025 | 17 |
| 33 | Nevada City Of WWTP | Nevada | 1.37 | — | IA0053648 | Apr 2030 | 2 |
| 34 | Webster City WWTP | Webster City | 1.36 | 8,531 | IA0036625 | Sep 2026 | 13 |
| 35 | Grinnell, City Of STP | Grinnell | 1.35 | 9,624 | IA0031186 | Nov 2029 | 0 |
| 36 | Independence WWTP | Independence | 1.31 | 6,236 | IA0036510 | Sep 2025 | 8 |
| 37 | Creston City Of STP | Creston | 1.25 | 8,188 | IA0035238 | Dec 2025 | 3 |
| 38 | Winterset City Of STP | Winterset | 1.16 | 5,353 | IA0034291 | Apr 2030 | 61 |
| 39 | Mount Pleasant WWTP | Mount Pleasant | 1.13 | 9,081 | IA0047970 | Jun 2029 | 0 |
| 40 | Vinton WWTP | Vinton | 1.11 | 5,495 | IA0035891 | Sep 2030 | 63 |
| 41 | City Of Shenandoah STP | Shenandoah | 1.1 | 5,824 | IA0032328 | Jan 2027 | 74 |
| 42 | Perry WWTP | Perry | 1.07 | 8,050 | IA0032379 | May 2030 | 2 |
| 43 | Estherville WWTP | Estherville | 1.05 | 7,156 | IA0023744 | Dec 2025 | 73 |
| 44 | Carroll WWTP | Carroll | 1.04 | 10,554 | IA0021377 | Aug 2027 | 1 |
| 45 | Iowa Falls WWTP | Iowa Falls | 1.02 | 5,106 | IA0023442 | Aug 2031 | 0 |
| 46 | City Of Sioux Center STP | Sioux Center | 0.97 | 6,846 | IA0033731 | Apr 2031 | 6 |
| 47 | Red Oak City Of STP | Red Oak | 0.96 | 5,945 | IA0040266 | Jan 2030 | 7 |
| 48 | Eldridge City Of STP (south Slope) | Eldridge | 0.96 | 2,650 | IA0063231 | Dec 2030 | 7 |
| 49 | Fairfield City Of STP | Fairfield | 0.93 | 10,210 | IA0035076 | May 2026 | 31 |
| 50 | Story City City Of STP | Story City | 0.93 | 3,352 | IA0035882 | Jul 2024 | 2 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
Largest plants 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 · MGD · NPDES permit · Anaerobic digester · Lift station · all terms
Cite this page
Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.
Klarifi. “The 50 largest wastewater treatment plants in Iowa (2026).” Updated October 26, 2026. https://klarifi.io/facilities/iowa/largestNeed a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.