Lagoon systems: wastewater treatment plants in South Dakota
109 plants · 84% of the state · 8 MGD reported by 19 plants
Klarifi identifies 109 publicly owned wastewater treatment plants with lagoon systems in South Dakota, 84% of the 130 plants in the state (8 MGD reported by 19 plants). The largest is Wilmot, City Of in Wilmot at 2.35 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 South Dakota
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Wilmot, City Of | Wilmot | 2.35 | SD0021024 | May 2027 | 24 |
| 2 | Vermillion, City Of | Vermillion | 1.06 | SD0020061 | Sep 2017 | 2 |
| 3 | Hartford, City Of | Hartford | 0.87 | SD0021750 | Dec 2024 | 117 |
| 4 | Frederick, Town Of | Frederick | 0.53 | SD0022152 | Sep 2024 | 49 |
| 5 | Harrisburg - City Of | Harrisburg, City Of | 0.48 | SD0023728 | Jun 2031 | 0 |
| 6 | Volga, City Of | Volga, City Of | 0.39 | SD0021920 | Dec 2028 | 36 |
| 7 | Oacoma, Town Of | Oacoma | 0.39 | SD0020737 | Dec 2027 | 5 |
| 8 | Beresford, City Of | Beresford | 0.3 | SD0020079 | May 2031 | 5 |
| 9 | Freeman, City Of | Freeman | 0.29 | SD0022110 | Jun 2027 | 3 |
| 10 | Summerset, City Of | Summerset | 0.21 | SD0027758 | Apr 2031 | 0 |
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 South Dakota
Lagoon systems in other states
Lagoon systems in South 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 October 26, 2026.
Wastewater terms: WWTP · POTW · Biosolids · FOG · Equalization tank · all terms