The 50 largest wastewater treatment plants in Colorado
Ranked by average flow · 103 MGD combined · 92% of the state's reported flow
Persigo Wastewater Treatment Plant in Grand Junction is the largest publicly owned wastewater treatment plant in Colorado by reported average flow, treating about 11.4 million gallons per day. The 50 plants below treat 103 MGD between them, 92% of the flow reported by all 137 plants in the state, and serve about 976,999 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 | Persigo Wastewater Treatment Plant | Grand Junction | 11.4 | 75,531 | CO0040053 | Dec 2022 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 1 |
| 2 | Greeley WWTP | Greeley | 9.4 | 109,084 | COL040258 | Dec 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons, Cooling towers | 13 |
| 3 | Big Dry Creek WWTP | Westminster | 6.9 | 122,100 | COR901608 | Jun 2029 | Clarifiers, Biogas silos | 388 |
| 4 | Parker Water + Sanitation District - North Water Reclamation Facility | Parker | 5.1 | 58,804 | COG072642 | Aug 2018 | Clarifiers, Biogas silos | 75 |
| 5 | Rainbow Park WWTP | Florence | 4.7 | 47,504 | CO0039748 | Feb 2020 | Clarifiers | 0 |
| 6 | South Ft. Collins Sanit. Dist. | Fort Collins | 4.23 | 14,153 | CO0020737 | Jan 2018 | Clarifiers, Carrousels / oxidation ditches, Biogas balloons | 1 |
| 7 | Fort Lupton WWTF | Fort Lupton | 3.86 | 7,974 | CO0021440 | Jun 2023 | Carrousels / oxidation ditches | 2 |
| 8 | Northglenn WWTP | Brighton | 3.65 | 38,973 | CO0036757 | Dec 2024 | Clarifiers | 10 |
| 9 | St Vrain Sanitation District | City Of Longmont | 3.55 | 52,634 | CO0041700 | Nov 2017 | — | 0 |
| 10 | Lafayette WWTF | Lafayette | 3.03 | 30,377 | COR900828 | Jun 2029 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 11 | Town Of Windsor Sewarage Treatment Plant | Windsor | 2.85 | 33,311 | CO0020320 | May 2020 | Clarifiers, Aerated lagoons | 0 |
| 12 | City Of Louisville | Louisville | 2.68 | 21,171 | CO0023078 | Sep 2016 | Clarifiers | 3 |
| 13 | Arapahoe County Water And Waste Water Authority | Englewood | 2.53 | 41,512 | COE015000 | Aug 2020 | Clarifiers, Uncovered lagoons | 0 |
| 14 | Steamboat Springs WWTP | Steamboat Springs | 2.22 | 26,851 | CO0020834 | Dec 2021 | Uncovered lagoons, Biogas silos | 27 |
| 15 | Breckenridge Sanitation District | Breckenridge | 1.96 | 5,061 | CO0021539 | Aug 2020 | — | 0 |
| 16 | Hill-N-Park STP | Greeley | 1.79 | 10,733 | CO0047287 | Dec 2023 | Clarifiers, Uncovered lagoons | 5 |
| 17 | Golden City Of | Jefferson County | 1.73 | — | CO0042170 | Sep 2017 | Aerated lagoons, Uncovered lagoons | 0 |
| 18 | Sterling City Of | Sterling | 1.64 | 13,998 | CO0026247 | Feb 2017 | Uncovered lagoons | 9 |
| 19 | San Juan (formerly Vista) WTP | Pagosa Springs | 1.63 | 12,577 | COG081215 | May 2028 | Clarifiers, Carrousels / oxidation ditches | 84 |
| 20 | Berthoud Town Of WWTP | Berthoud | 1.61 | 10,512 | CO0046663 | Jul 2020 | Clarifiers | 16 |
| 21 | Aspen Consolidated Sanitation District | Aspen | 1.4 | 6,995 | CO0026387 | Apr 2031 | Aerated lagoons | 10 |
| 22 | Delta WWTP | Delta | 1.33 | 10,180 | COR900345 | Jun 2029 | — | 1 |
| 23 | Clifton #2 West WWTP | Clifton | 1.3 | 22,678 | CO0033791 | Mar 2020 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches | 0 |
| 24 | Upper Monument Crk Reg WWTF | Colorado Springs | 1.17 | 9,930 | CO0042030 | Apr 2020 | — | 39 |
| 25 | Woodmen Hills Metro Dist WWTF | Peyton | 1.16 | 18,281 | CO0047091 | Jan 2020 | Uncovered lagoons | 0 |
| 26 | Telluride Regional WWTF | Telluride | 1.13 | 9,000 | CO0041840 | Nov 2025 | — | 94 |
| 27 | Craig WWTF | Craig | 1.09 | 9,048 | CO0040037 | Feb 2021 | Clarifiers, Carrousels / oxidation ditches | 0 |
| 28 | Regional WWTF | Alamosa | 1.09 | 9,743 | CO0044458 | Oct 2019 | Aerated lagoons, Uncovered lagoons | 4 |
| 29 | Harold D Thompson Regional WW Reclamation Facility | Fountain | 1.08 | 3,400 | CO0000005 | Jun 2018 | Clarifiers | 5 |
| 30 | Fruita Wastewater Reclamation Facility | Fruita | 1.07 | 13,408 | CO0048854 | Sep 2025 | Clarifiers, Carrousels / oxidation ditches | 2 |
| 31 | Pinery WWTF | Parker | 1.04 | 9,741 | CO0041092 | Oct 2016 | Uncovered lagoons, Carrousels / oxidation ditches | 2 |
| 32 | City Of Trinidad | Trinidad | 1.02 | 8,340 | CO0031232 | Apr 2020 | Clarifiers, Uncovered lagoons | 0 |
| 33 | Rifle Reg. WW Reclamation Fac. | Rifle | 1 | 10,420 | CO0048151 | Mar 2020 | Carrousels / oxidation ditches | 2 |
| 34 | Vail WWTP | Vail | 1 | — | CO0021369 | Feb 2026 | — | 7 |
| 35 | Upper Thompson WWTP | Estes Park | 0.88 | 10,000 | CO0031844 | Sep 2024 | Clarifiers | 1 |
| 36 | Southwest WWTF | Cortez | 0.79 | 8,762 | CO0027545 | Jan 2018 | Clarifiers | 0 |
| 37 | City Of Salida WWTP | Salida | 0.78 | 6,635 | CO0040339 | Nov 2024 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 38 | Stonegate Village Metro Dist | Parker | 0.74 | 9,741 | COE011000 | Aug 2020 | — | 3 |
| 39 | Lake City Area STP | Lake City | 0.72 | 436 | COG081214 | May 2028 | Aerated lagoons, Uncovered lagoons | 33 |
| 40 | Las Animas WWTP | Las Animas | 0.71 | 2,290 | CO0040690 | Jan 2026 | Aerated lagoons, Uncovered lagoons | 73 |
| 41 | Gypsum WWTF | Gypsum | 0.7 | 8,078 | COG080991 | May 2025 | — | 126 |
| 42 | Woodland Park City Of | Woodland Park | 0.64 | — | CO0043214 | Oct 2020 | — | 1 |
| 43 | Buena Vista Sanitation District WWTF | Buena Vista | 0.62 | 4,213 | CO0045748 | Oct 2020 | Uncovered lagoons, Biogas balloons | 1 |
| 44 | Estes Park Sanitation District | Estes Park | 0.6 | 5,886 | CO0020290 | Dec 2020 | — | 21 |
| 45 | Evergreen WWTP | Evergreen | 0.59 | 8,309 | CO0031429 | Mar 2018 | — | 0 |
| 46 | Table Mountain WWTF | Grand Lake | 0.59 | 8,000 | CO0037681 | Apr 2031 | — | 1 |
| 47 | Low Point WWTP | Johnstown | 0.55 | 17,320 | CO0047058 | Apr 2017 | — | 0 |
| 48 | Milliken Sanitation District | Milliken | 0.53 | 8,493 | CO0042528 | Jul 2020 | Aerated lagoons, Uncovered lagoons | 2 |
| 49 | Mt Cb Water + Sanitation District Water Treatment Plant Expansion | Mount Crested Butte | 0.53 | 938 | CO0027171 | Jan 2025 | — | 28 |
| 50 | Rocky Ford Sewage Lagoons | Rocky Ford | 0.52 | 3,874 | CO0023850 | Jul 2020 | Aerated lagoons, Uncovered lagoons | 63 |
Largest plants in Colorado: 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.