The 5 largest wastewater treatment plants in North Dakota
Ranked by average flow · 25 MGD combined · 100% of the state's reported flow
Grand Forks City Of in Grand Forks is the largest publicly owned wastewater treatment plant in North Dakota by reported average flow, treating about 8.82 million gallons per day. The 5 plants below treat 25 MGD between them, 100% of the flow reported by all 197 plants in the state, and serve about 230,858 people. Every plant links to its profile with permit, technology and compliance data.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|---|
| 1 | Grand Forks City Of | Grand Forks | 8.82 | 70,278 | ND0022888 | Dec 2028 | Uncovered lagoons | 7 |
| 2 | Bismarck City Of (potw) | Bismarck | 7.66 | 75,230 | ND0023434 | Jun 2028 | Uncovered lagoons, Biogas balloons | 0 |
| 3 | City Of Minot - Minot Landfill | Minot | 4.26 | 47,201 | ND0022896 | Mar 2030 | — | 19 |
| 4 | Williston City Of | Williston | 2.88 | 16,988 | ND0022349 | Mar 2028 | Uncovered lagoons | 4 |
| 5 | Mandan Landfill / Ts | Mandan | 1.77 | 21,161 | ND0022861 | Sep 2026 | — | 0 |
Largest plants in North Dakota: 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.