Lagoon systems: wastewater treatment plants in Arizona
25 plants · 47% of the state · 120 MGD reported by 11 plants
Klarifi identifies 25 publicly owned wastewater treatment plants with lagoon systems in Arizona, 47% of the 53 plants in the state (120 MGD reported by 11 plants). The largest is 91st Avenue WWTP in Tolleson at 78.71 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 Arizona
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | 91st Avenue WWTP | Tolleson | 78.71 | AZ0020524 | Apr 2028 | 2 |
| 2 | Pima County - Ina Road WWTP | Tucson | 31.89 | AZ0020001 | May 2027 | 3 |
| 3 | Casa Grande WRF | Casa Grande | 3.54 | AZ0025178 | Sep 2029 | 29 |
| 4 | Town Of Prescott Valley - WWTP | Prescott Valley | 2.74 | AZ0025381 | Feb 2027 | 0 |
| 5 | Kayenta WWTF | Kayenta | 1.46 | NN0020281 | Jan 2029 | 144 |
| 6 | Joint Venture WWTF | Parker | 0.54 | AZ0021415 | Nov 2026 | 165 |
| 7 | Tuba City WWTP | Tuba City | 0.42 | NN0020290 | Apr 2027 | 138 |
| 8 | Window Rock Wastewater Treatment Facility | Fort Defiance | 0.39 | NN0021555 | Sep 2026 | 15 |
| 9 | Quartzsite, Town Of - WWTP | Quartzsite | 0.2 | AZ0023752 | Aug 2027 | 6 |
| 10 | Town Of Gila Bend - WWTP | Gila Bend | 0.18 | AZ0020231 | Jun 2030 | 86 |
| 11 | Tusayan Sanitary District | Grand Canyon | 0.03 | AZ0026719 | Aug 2027 | 0 |
| 12 | Apache Junction WWTP | Apache Junction | — | AZ0023931 | Jul 2029 | 0 |
| 13 | Benson, City Of - WWTF | Benson | — | AZ0026026 | Nov 2026 | 0 |
| 14 | Bullhead City, City Of - Section 10 WWTP | Bullhead City | — | AZ0026808 | Oct 2026 | 0 |
| 15 | City Of Williams - WWTP | Williams | — | AZ0025755 | Oct 2029 | 0 |
| 16 | City Of Winslow - WWTP | Winslow | — | AZ0026310 | Feb 2031 | 0 |
| 17 | Ganado WWTP | Ganado | — | NN0022195 | Jul 2026 | 0 |
| 18 | North Florence Wwtp, Town Of Florence | Florence | — | AZ0025194 | Nov 2025 | 11 |
| 19 | Pima County - Wwmd - Avra Valley WWTF | Tucson | — | AZ0024121 | May 2029 | 0 |
| 20 | Pima County - Wwmd - Green Valley Bnro - WWTP | Sahuarita | — | AZ0024937 | Mar 2031 | 0 |
| 21 | Six Mile Lagoon Wastewater Treatment Facility | Peridot | — | AZ0024640 | Jun 2030 | 848 |
| 22 | Tolleson WWTP | Tolleson | — | AZ0020338 | Feb 2031 | 30 |
| 23 | Town Of Cave Creek - WRF | Cave Creek | — | AZ0025828 | Oct 2029 | 0 |
| 24 | Town Of Florence WWTP | Florence | — | AZ0025208 | Apr 2031 | 23 |
| 25 | Town Of Marana Water Reclamation Facility | Marana | — | AZ0024520 | Aug 2027 | 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 Arizona
Lagoon systems in other states
Lagoon systems in Arizona: 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.