What is the largest wastewater treatment plant in Arizona?

91st Avenue WWTP in Tolleson, treating an average of 78.71 MGD under NPDES permit AZ0020524. 23rd Avenue Wastewater Treatment Plant in Phoenix is second at 35.67 MGD.

How much wastewater do Arizona’s largest plants treat?

The 35 largest plants treat 178 MGD combined, 100% of the flow reported by all 53 publicly owned plants in Arizona.

How is plant size measured?

By reported average daily flow in million gallons per day (MGD) from EPA discharge monitoring reports, the standard measure of a plant’s size. Design capacity, the flow a plant is permitted to treat, is usually higher and is shown on each profile.

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The 35 largest wastewater treatment plants in Arizona

Name: Largest wastewater treatment plants in Arizona
Creator: Klarifi
License: https://klarifi.io/terms-of-service

Ranked by average flow · 178 MGD combined · 100% of the state's reported flow

91st Avenue WWTP in Tolleson is the largest publicly owned wastewater treatment plant in Arizona by reported average flow, treating about 78.71 million gallons per day. The 35 plants below treat 178 MGD between them, 100% of the flow reported by all 53 plants in the state, and serve about 2,391,200 people. Every plant links to its profile with permit, technology and compliance data.

All plants in Arizona →The 100 largest US plants →Arizona NPDES permits →

The 35 largest publicly owned wastewater treatment plants in Arizona by average flow (MGD), with population served, NPDES permit, expiry, treatment technology and three-year violation count.
#	Facility	City	Avg flow (MGD)	Population	NPDES permit	Expires	Technology	Violations (3y)
1	91st Avenue WWTP	Tolleson	78.71	—	AZ0020524	Apr 2028	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos	2
2	23rd Avenue Wastewater Treatment Plant	Phoenix	35.67	1,604,039	AZ0020559	Jun 2029	Clarifiers, Biogas silos	2
3	Pima County - Ina Road WWTP	Tucson	31.89	400,657	AZ0020001	May 2027	Clarifiers, Uncovered lagoons, Biogas silos	3
4	Yuma, City Of - Figueroa Ave WPCF	Yuma	7.27	82,721	AZ0020443	Aug 2028	Clarifiers, Biogas silos	14
5	Casa Grande WRF	Casa Grande	3.54	55,358	AZ0025178	Sep 2029	Clarifiers, Covered lagoons, Uncovered lagoons, Carrousels / oxidation ditches	29
6	Town Of Prescott Valley - WWTP	Prescott Valley	2.74	55,332	AZ0025381	Feb 2027	Clarifiers, Aerated lagoons, Carrousels / oxidation ditches, Biogas silos	0
7	Northwest Wrp	Mesa	2.72	—	AZ0024031	Nov 2029	—	6
8	Goodyear, City Of - 157th Ave WWTP	Goodyear	2.5	80,313	AZ0022357	Mar 2027	Carrousels / oxidation ditches	1
9	Town Of Buckeye - Sundance Wwrf	Buckeye	2.02	—	AZ0024881	Apr 2029	—	37
10	Kayenta WWTF	Kayenta	1.46	—	NN0020281	Jan 2029	Uncovered lagoons	144
11	Buckeye WWTP	Buckeye	1.38	45,732	AZ0025313	Oct 2030	Clarifiers, Carrousels / oxidation ditches	1
12	Cottonwood WWTF	Cottonwood	1.04	10,540	AZ0024716	Apr 2027	Clarifiers	16
13	City Of Safford - Gila Resources Wrp	Safford	0.78	11,900	AZ0024911	Jun 2029	Clarifiers, Carrousels / oxidation ditches	0
14	Chinle WWTF	Chinle	0.71	—	NN0020265	Aug 2023	—	160
15	American Gulch Wastewater Treatment Plant	Payson	0.69	16,805	AZ0020117	Apr 2027	Clarifiers	0
16	City Of Somerton - WWTP	Somerton	0.65	—	AZ0026603	Dec 2029	Clarifiers	0
17	Whiteriver Sewage Lagoon	Whiteriver	0.58	—	AZ0024058	Oct 2026	—	486
18	Tucson Airport Remediation Project - Co-Mingled Plume	Tucson	0.56	—	AZ0026417	Oct 2026	—	0
19	Joint Venture WWTF	Parker	0.54	5,602	AZ0021415	Nov 2026	Uncovered lagoons	165
20	Tuba City WWTP	Tuba City	0.42	—	NN0020290	Apr 2027	Aerated lagoons, Uncovered lagoons	138
21	Window Rock Wastewater Treatment Facility	Fort Defiance	0.39	—	NN0021555	Sep 2026	Aerated lagoons, Uncovered lagoons	15
22	Pinal Creek WWTP	Globe	0.35	8,727	AZ0020249	Mar 2031	—	9
23	Festival Ranch WRF	Buckeye	0.28	—	AZ0025216	Oct 2028	—	3
24	City Of Peoria	Peoria	0.23	—	AZ0024945	Jul 2027	Biogas silos	17
25	City Of Kingman - Downtown Pond	Kingman	0.23	2,500	AZ0026018	Dec 2026	—	7
26	Quartzsite, Town Of - WWTP	Quartzsite	0.2	—	AZ0023752	Aug 2027	Aerated lagoons, Uncovered lagoons	6
27	Town Of Gila Bend - WWTP	Gila Bend	0.18	1,938	AZ0020231	Jun 2030	Aerated lagoons, Uncovered lagoons	86
28	Town Of Superior Wastewater Treatment Plant (wwtp)	Superior	0.13	3,193	AZ0021199	Apr 2028	—	19
29	Yuma Main Street Treatment Plant	Yuma	0.12	—	AZ0025411	May 2027	—	1
30	Town Of Kearny Wastewater Reclamation Facility	Kearny	0.1	2,185	AZ0024449	Jul 2026	Biogas silos	49
31	Town Of Patagonia - WWTP	Patagonia	0.05	706	AZ0025011	Jul 2030	—	0
32	City Of Tombstone - WWTP	Tombstone	0.05	1,641	AZ0025577	Mar 2031	Clarifiers, Carrousels / oxidation ditches	12
33	Tusayan Sanitary District	Grand Canyon	0.03	—	AZ0026719	Aug 2027	Clarifiers, Covered lagoons, Uncovered lagoons, Biogas silos, Biogas balloons	0
34	City Of Mesa - Greenfield Water Reclamation Plant	Gilbert	0.03	—	AZ0025241	Sep 2029	Biogas balloons	0
35	Winkelman WWTP	Winkelman	0.02	1,311	AZ0020176	May 2029	—	24

Largest plants 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.

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