Lagoon systems: wastewater treatment plants in Minnesota
341 plants · 74% of the state · 45 MGD reported by 69 plants
Klarifi identifies 341 publicly owned wastewater treatment plants with lagoon systems in Minnesota, 74% of the 460 plants in the state (45 MGD reported by 69 plants). The largest is Met Council - Empire WWTP in Farmington at 12.05 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 Minnesota
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Met Council - Empire WWTP | Farmington | 12.05 | MNL045845 | Dec 2030 | 0 |
| 2 | Grand Rapids WWTP | Grand Rapids | 5.8 | MN0022080 | Jan 2025 | 6 |
| 3 | Moorhead Wastewater Treatment Facility | Moorhead | 3.82 | MN0049069 | Jun 2026 | 0 |
| 4 | Marshall WWTP | Marshall | 2.51 | MN0022179 | Feb 2029 | 16 |
| 5 | Saint Peter WWTP | Saint Peter | 1.9 | MN0022535 | Mar 2027 | 15 |
| 6 | Long Prairie WWTP | Long Prairie | 1.51 | MN0066079 | Apr 2023 | 2 |
| 7 | Buffalo WWTP | Buffalo | 1.23 | MNL040649 | Dec 2030 | 1 |
| 8 | Cold Spring WWTP | Cold Spring | 1.16 | MNL023094 | Dec 2030 | 0 |
| 9 | Rogers WWTP | Rogers | 1.09 | MN0029629 | Mar 2026 | 5 |
| 10 | Chisago Lakes Joint Stc | Chisago City | 1.03 | MN0055808 | Mar 2030 | 3 |
| 11 | Smsc Water Reclamation Facili | Prior Lake | 0.74 | MN0067938 | Apr 2023 | 7 |
| 12 | New Prague WWTP | New Prague | 0.7 | MNL020150 | Dec 2030 | 9 |
| 13 | Chisholm WWTP | Chisholm | 0.64 | MN0020117 | Jan 2027 | 10 |
| 14 | Stewartville WWTP | Stewartville | 0.6 | MN0020681 | Nov 2029 | 4 |
| 15 | Whitewater River Regional WWTP | Saint Charles | 0.58 | MN0046868 | Oct 2027 | 13 |
| 16 | Albertville WWTP | Albertville | 0.58 | MN0050954 | May 2024 | 0 |
| 17 | Delano WWTP | Delano | 0.54 | MN0051250 | Mar 2023 | 76 |
| 18 | Pelican Rapids WWTP | Pelican Rapids | 0.53 | MN0022225 | Nov 2029 | 4 |
| 19 | Zumbrota WWTP | Zumbrota | 0.49 | MNL025330 | Dec 2030 | 84 |
| 20 | Cokato WWTP | Cokato | 0.47 | MN0049204 | Mar 2027 | 8 |
| 21 | Belle Plaine WWTP | Belle Plaine | 0.43 | MN0022772 | May 2027 | 30 |
| 22 | Saint Francis WWTP | Saint Francis | 0.39 | MN0021407 | Jun 2026 | 8 |
| 23 | Montrose WWTP | Montrose | 0.39 | MN0024228 | Jan 2023 | 3 |
| 24 | North Branch WWTP | North Branch | 0.37 | MN0024350 | Apr 2025 | 0 |
| 25 | Zimmerman WWTP | Zimmerman | 0.35 | MN0042331 | May 2031 | 61 |
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 Minnesota
Lagoon systems in other states
Lagoon systems in Minnesota: 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.