National Pollutant Discharge Elimination System (NPDES)

Status of Nutrient Requirements for NPDES-Permitted Facilities

Discharges from municipal wastewater treatment facilities with little to no treatment for nitrogen and phosphorus are a significant source of these nutrients to surface waters throughout the country. Setting permit limits and treating the wastewater to meet specific effluent limits can substantially reduce nitrogen and phosphorus loading from these facilities, protecting local and downstream water quality as a result. The data in this indicator represent major (≥1 million gallons/day (MGD)) and non-major ("minor," <1 MGD) municipal wastewater treatment facilities with individual National Pollutant Discharge Elimination System (NPDES) permits.

Presented by state or territory of the U.S. are the counts and percentages of such facilities that have permit limits¹ or monitoring requirements only, for any nutrient pollution parameter. Please refer to the data protocol document, "Nutrient Data Compilation and Analysis Outline," for details on how the data were generated and produced.

The data tables are based on February 2016 data from EPA's Integrated Compliance Information System (ICIS) database.

View and download a pdf version of the nutrient data tables.
View and download a pdf version of the protocol to learn how EPA constructed the nutrient data tables.

Majors
with Limits
Non-Majors
with Limits
Majors with
Monitoring Requirements
Non-Majors with
Monitoring Requirements

Table 1. Number and Percent of Major Municipal Sewage Treatment Facilities with Numeric Effluent Limits for Nitrogen (N) and/or Phosphorus (P)

This table presents the total number of individual permitted WWTFs that have nitrogen limits only, phosphorus limits only, or have limits for both pollutants. These data include all individual, non-stormwater NPDES permitted facilities with data in ICIS as of February 2016. (The data include EPA-issued permits and tribal permits. The data only include limits with measuring units that are either mass-based or concentration-based. WWTFs are publicly-owned treatment works (POTWs) with the primary permit standard industrial classification ("SIC") code 4952, and where there is no SIC code, the Facility Type Indicator field is labled "POTW.")

EPA Region	State	Universe of Majors	Nitrogen Only (Number)	Nitrogen Only (Percent)	Phosphorus Only (Number)	Phosphorus Only (Percent)	Both N and P (Number)	Both N and P (Percent)	Any (N or P or Both) (Number)	Any (N or P or Both) (Percent)
10	AK	20	0	0	0	0	0	0	0	0
4	AL	119	19	16	3	3	14	12	36	30
6	AR	78	2	3	9	12	7	9	18	23
9	AS⁽⁴⁾	2	0	0	0	0	0	0	0	0
9	AZ	48	2	4	1	2	3	6	6	13
9	CA	175	68	39	0	0	7	4	75	43
8	CO	91	12	13	6	7	5	5	23	25
1	CT⁽²⁾	64	1	2	13	20	0	0	14	22
3	DC	2	0	0	1	50	0	0	1	50
3	DE	8	0	0	0	0	5	63	5	63
4	FL⁽⁵⁾	94	13	14	1	1	51	54	65	69
4	GA	151	0	0	74	49	0	0	74	49
6	GM	0	0	0	0	0	0	0	0	0
9	GU	3	0	0	0	0	0	0	0	0
9	HI	2	1	50	0	0	0	0	1	50
7	IA^(3),(6)	96	13	14	1	1	0	0	14	15
10	ID	28	0	0	14	50	1	4	15	54
5	IL	214	0	0	58	27	0	0	58	27
5	IN	133	0	0	58	44	0	0	58	44
7	KS	45	0	0	0	0	0	0	0	0
4	KY	87	0	0	22	25	0	0	22	25
6	LA	105	0	0	0	0	0	0	0	0
1	MA	91	1	1	45	49	8	9	54	59
3	MD	47	1	2	1	2	41	87	43	91
1	ME	61	0	0	5	8	0	0	5	8
5	MI	105	0	0	105	100	0	0	105	100
5	MN	75	0	0	50	67	0	0	50	67
7	MO	123	1	1	8	7	0	0	9	7
9	MP⁽⁴⁾	2	0	0	0	0	2	100	2	100
4	MS	65	0	0	0	0	16	25	16	25
8	MT	21	2	10	0	0	11	52	13	62
4	NC⁽²⁾	147	1	1	23	16	4	3	28	19
8	ND⁽³⁾	16	0	0	1	6	0	0	1	6
7	NE	30	1	3	0	0	0	0	1	3
1	NH	36	2	6	14	39	0	0	16	44
2	NJ^(3),(7)	92	0	0	28	30	7	8	35	38
6	NM	22	2	9	1	5	1	5	4	18
9	NV	7	1	14	1	14	1	14	3	43
2	NY	211	30	14	64	30	5	2	99	47
5	OH	205	0	0	101	49	5	2	106	52
6	OK	69	3	4	2	3	0	0	5	7
10	OR	50	0	0	4	8	0	0	4	8
3	PA	291	0	0	35	12	109	37	144	49
2	PR⁽⁴⁾	33	13	39	1	3	16	48	30	91
1	RI	19	6	32	1	5	5	26	12	63
4	SC	98	0	0	16	16	0	0	16	16
8	SD	20	0	0	0	0	0	0	0	0
4	TN	107	2	2	1	1	15	14	18	17
6	TX⁽⁸⁾	489	3	1	29	6	1	0	33	7
8	UT	29	0	0	2	7	0	0	2	7
3	VA⁽²⁾	92	10	11	4	4	40	43	54	59
2	VI⁽⁴⁾	2	0	0	0	0	0	0	0	0
1	VT⁽³⁾	0	0	0	0	0	0	0	0	0
10	WA⁽³⁾	48	1	2	2	4	0	0	3	6
5	WI	86	0	0	86	100	0	0	86	100
3	WV	50	3	6	2	4	6	12	11	22
8	WY⁽³⁾	16	0	0	0	0	0	0	0	0
Total		4,420	214	5	893	20	386	9	1,493	34

Notes:
(1) Note that all permits with limits should also have corresponding monitoring requirements for each parameter that is limited to track compliance.
(2) These states have watershed-based permitting for multiple dischargers for nutrients. These permits/facilities may not be reflected in this table. (VA - approximately 112 WWTFs covered for N & P; NC - approximately 54 WWTF covered for N; and CT - approximately 79 facilities covered for N)
(3) IA, ND, VT, WA, and WY did not have primary SIC codes entered into the Permit Basic Info section of ICIS for most or all of their facilities. NJ has only entered SIC codes for 46 percent of its individual permittees in ICIS.
(4) The following territories and regions are included in these tables: American Samoa (AS), Gulf of Mexico (GM), Guam (GU), Northern Mariana Islands (MP), Puerto Rico (PR), and U.S. Virgin Islands (VI).
(5) Upon review, this state indicated that it uses other monitoring location codes in addition to the ones used for this analysis. [FL]
(6) Iowa is in the process of transitioning to a new NPDES database and is working to ensuring accurate transfer and migration of required data into the EPA ICIS-NPDES data system. This process is expected to be complete by summer 2017.
(7) This state noted that its data are batch-loaded into ICIS, and therefore there are some errors based on the state's records. [NJ]
(8) This state indicated that the data managed to capture 12 permits that are either for stormwater (MS4) or industrial facilities. [TX]

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Table 2. Number and Percent of Non-major Municipal Sewage Treatment Facilities with Numeric Effluent Limits for Nitrogen (N) and/or Phosphorus (P)

Note that at the time of this data collection from ICIS-NPDES, data for non-major facilities were not required to be entered into the system. Therefore, the data below represent what was in the system at the time of the collection, and may not reflect the entire universe of facilities as well as limit and monitoring requirements.

EPA Region	State	Universe of Non-majors	Nitrogen Only (Number)	Nitrogen Only (Percent)	Phosphorus Only (Number)	Phosphorus Only (Percent)	Both N and P (Number)	Both N and P (Percent)	Any (N or P or Both) (Number)	Any (N or P or Both) (Percent)
10	AK	7	0	0	0	0	0	0	0	0
4	AL	259	26	10	11	4	8	3	45	17
6	AR	311	4	1	13	4	3	1	20	6
9	AS⁽⁴⁾	0	0	0	0	0	0	0	0	0
9	AZ	57	4	7	0	0	4	7	8	14
9	CA	85	14	16	0	0	1	1	15	18
8	CO	156	9	6	11	7	2	1	22	14
1	CT⁽²⁾	23	4	17	10	43	0	0	14	61
3	DC	0	0	0	0	0	0	0	0	0
3	DE	7	0	0	1	14	3	43	4	57
4	FL⁽⁵⁾	80	12	15	2	3	33	41	47	59
4	GA	192	0	0	31	16	1	1	32	17
6	GM⁽⁴⁾	0	0	0	0	0	0	0	0	0
9	GU⁽⁴⁾	3	0	0	0	0	2	67	2	67
9	HI	0	0	0	0	0	0	0	0	0
7	IA^(3),(6)	703	114	16	1	0	0	0	115	16
10	ID	90	2	2	20	22	2	2	24	27
5	IL	398	1	0	25	6	1	0	27	7
5	IN	369	0	0	65	18	0	0	65	18
7	KS	418	1	0	0	0	1	0	2	0
4	KY	182	0	0	26	14	0	0	26	14
6	LA	364	1	0	0	0	1	0	2	1
1	MA	29	1	3	12	41	0	0	13	45
3	MD	127	6	5	7	6	37	29	50	39
1	ME	71	1	1	0	0	0	0	1	1
5	MI	162	0	0	130	80	0	0	130	80
5	MN	287	0	0	5	2	0	0	5	2
7	MO	1,316	2	0	52	4	1	0	55	4
9	MP⁽⁴⁾	1	0	0	0	0	0	0	0	0
4	MS	292	0	0	1	0	16	5	17	6
8	MT	86	7	8	0	0	18	21	25	29
4	NC⁽²⁾	264	0	0	21	8	1	0	22	8
8	ND⁽³⁾	29	0	0	0	0	0	0	0	0
7	NE	266	7	3	0	0	0	0	7	3
1	NH	13	0	0	8	62	0	0	8	62
2	NJ^(3),(7)	141	0	0	33	23	5	4	38	27
6	NM	37	1	3	1	3	4	11	6	16
9	NV	7	2	29	0	0	3	43	5	71
2	NY	388	16	4	73	19	1	0	90	23
5	OH	1,083	2	0	113	10	5	0	120	11
6	OK	201	0	0	6	3	0	0	6	3
10	OR	132	0	0	0	0	0	0	0	0
3	PA	672	0	0	2	0	75	11	77	11
2	PR⁽⁴⁾	17	1	6	2	12	14	82	17	100
1	RI	0	0	0	0	0	0	0	0	0
4	SC	66	0	0	1	2	0	0	1	2
8	SD	171	1	1	0	0	1	1	2	1
4	TN	299	3	1	3	1	16	5	22	7
6	TX⁽⁸⁾	1,323	2	0	32	2	3	0	37	3
8	UT	32	0	0	2	6	0	0	2	6
3	VA⁽²⁾	255	0	0	0	0	1	0	1	0
2	VI⁽⁴⁾	12	0	0	5	42	0	0	5	42
1	VT⁽³⁾	1	0	0	0	0	0	0	0	0
10	WA⁽³⁾	193	1	1	0	0	2	1	3	2
5	WI	467	0	0	8	2	0	0	8	2
3	WV	239	38	16	1	0	16	7	55	23
8	WY⁽³⁾	57	0	0	0	0	0	0	0	0
Total		12,440	283	2	734	6	281	2	1,298	10

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Table 3. Number and Percent of Major Municipal Sewage Treatment Facilities with Nitrogen (N) and/or Phosphorus (P) Monitoring Requirements for Monitoring Only Purposes or for Compliance with an Effluent Limit

This table represents the total number of individual permitted WWTFs that have monitoring requirements for nitrogen only, phosphorus only, or have monitoring requirements for both pollutants. These data include all individual, non-stormwater NPDES permitted facilities with data in ICIS as of February 2016. (These data include EPA-issued permits and tribal permits. These data only include requirements with measuring units that are either mass-based or concentration-based. WWTFs are publicly-owned treatment works (POTWs) with the primary permit standard industrial classification ("SIC") code 4952, and where there is no SIC code, the Facility Type Indicator field is labled "POTW.")

EPA Region	State	Universe of Majors	Nitrogen Only (Number)	Nitrogen Only (Percent)	Phosphorus Only (Number)	Phosphorus Only (Percent)	Both N and P (Number)	Both N and P (Percent)	Any (N or P or Both) (Number)	Any (N or P or Both) (Percent)
10	AK	20	1	5	0	0	0	0	1	5
4	AL	119	0	0	0	0	119	100	119	100
6	AR	78	6	8	9	12	51	65	66	85
9	AS⁽⁴⁾	2	0	0	0	0	0	0	0	0
9	AZ	48	0	0	0	0	43	90	43	90
9	CA	175	26	15	2	1	116	66	144	82
8	CO	91	26	29	3	3	5	5	34	37
1	CT⁽²⁾	64	0	0	42	66	2	3	44	69
3	DC	2	0	0	0	0	2	100	2	100
3	DE	8	1	13	0	0	4	50	5	63
4	FL⁽⁵⁾	94	3	3	8	9	35	37	46	49
4	GA	151	0	0	78	52	43	28	121	80
6	GM⁽⁴⁾	0	0	0	0	0	0	0	0	0
9	GU⁽⁴⁾	3	0	0	0	0	0	0	0	0
9	HI	2	0	0	0	0	2	100	2	100
7	IA^(3),(6)	96	2	2	5	5	51	53	58	60
10	ID	28	1	4	3	11	22	79	26	93
5	IL	214	27	13	20	9	149	70	196	92
5	IN	133	1	1	75	56	13	10	89	67
7	KS	45	0	0	0	0	45	100	45	100
4	KY	87	10	11	10	11	66	76	86	99
6	LA	105	0	0	1	1	12	11	13	12
1	MA	91	21	23	18	20	43	47	82	90
3	MD	47	0	0	0	0	47	100	47	100
1	ME	61	0	0	14	23	0	0	14	23
5	MI	105	0	0	20	19	0	0	20	19
5	MN	75	15	20	9	12	50	67	74	99
7	MO	123	3	2	1	1	30	24	34	28
9	MP⁽⁴⁾	2	0	0	0	0	0	0	0	0
4	MS	65	0	0	0	0	61	94	61	94
8	MT	21	1	5	0	0	20	95	21	100
4	NC⁽²⁾	147	24	16	0	0	106	72	130	88
8	ND⁽³⁾	16	0	0	0	0	8	50	8	50
7	NE	30	0	0	0	0	24	80	24	80
1	NH	36	6	17	15	42	2	6	23	64
2	NJ^(3),(7)	92	2	2	17	18	44	48	63	68
6	NM	22	1	5	1	5	1	5	3	14
9	NV	7	1	14	0	0	6	86	7	100
2	NY	211	83	39	8	4	90	43	181	86
5	OH	205	79	39	1	0	120	59	200	98
6	OK	69	2	3	0	0	1	1	3	4
10	OR	50	2	4	0	0	26	52	28	56
3	PA	291	12	4	8	3	196	67	216	74
2	PR⁽⁴⁾	33	5	15	0	0	0	0	5	15
1	RI	19	10	53	0	0	9	47	19	100
4	SC	98	18	18	3	3	56	57	77	79
8	SD	20	6	30	0	0	5	25	11	55
4	TN	107	2	2	0	0	83	78	85	79
6	TX⁽⁸⁾	489	7	1	9	2	6	1	22	4
8	UT	29	0	0	1	3	23	79	24	83
3	VA⁽²⁾	92	12	13	3	3	22	24	37	40
2	VI⁽⁴⁾	2	0	0	2	100	0	0	2	100
1	VT⁽³⁾	0	0	0	0	0	0	0	0	0
10	WA⁽³⁾	48	2	4	1	2	35	73	38	79
5	WI	86	0	0	69	80	17	20	86	100
3	WV	50	0	0	0	0	18	36	18	36
8	WY⁽³⁾	16	1	6	1	6	0	0	2	13
Total		4,420	419	9	457	10	1,929	44	2,805	63

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Table 4. Number and Percent of Non-major Municipal Sewage Treatment Facilities with Nitrogen (N) and/or Phosphorus (P) Monitoring Requirements for Monitoring Only Purposes or for Compliance with an Effluent Limit

Note that at the time of this data collection from ICIS-NPDES, data for non-major facilities were not required to be entered into the system. Therefore, the data below represent what was in the system at the time of the collection and may not reflect the entire universe of facilities as well as limit and monitoring requirements.

EPA Region	State	Universe of Non-majors	Nitrogen Only (Number)	Nitrogen Only (Percent)	Phosphorus Only (Number)	Phosphorus Only (Percent)	Both N and P (Number)	Both N and P (Percent)	Any (N or P or Both) (Number)	Any (N or P or Both) (Percent)
10	AK	7	0	0	0	0	1	14	1	14
4	AL	259	0	0	1	0	258	100	259	100
6	AR	311	3	1	7	2	7	2	17	5
9	AS⁽⁴⁾	0	0	0	0	0	0	0	0	0
9	AZ	57	1	2	1	2	42	74	44	77
9	CA	85	5	6	5	6	21	25	31	36
8	CO	156	23	15	11	7	7	4	41	26
1	CT⁽²⁾	23	0	0	12	52	3	13	15	65
3	DC	0	0	0	0	0	0	0	0	0
3	DE	7	0	0	0	0	4	57	4	57
4	FL⁽⁵⁾	80	4	5	4	5	34	43	42	53
4	GA	192	5	3	25	13	13	7	43	22
6	GM⁽⁴⁾	0	0	0	0	0	0	0	0	0
9	GU⁽⁴⁾	3	0	0	0	0	0	0	0	0
9	HI	0	0	0	0	0	0	0	0	0
7	IA^(3),(6)	703	0	0	2	0	6	1	8	1
10	ID	90	1	1	33	37	22	24	56	62
5	IL	398	14	4	47	12	11	3	72	18
5	IN	369	0	0	28	8	0	0	28	8
7	KS	418	4	1	89	21	111	27	204	49
4	KY	182	19	10	3	2	142	78	164	90
6	LA	364	0	0	0	0	13	4	13	4
1	MA	29	8	28	3	10	9	31	20	69
3	MD	127	1	1	1	1	84	66	86	68
1	ME	71	2	3	2	3	0	0	4	6
5	MI	162	0	0	39	24	0	0	39	24
5	MN	287	1	0	8	3	2	1	11	4
7	MO	1,316	30	2	50	4	92	7	172	13
9	MP⁽⁴⁾	1	0	0	0	0	0	0	0	0
4	MS	292	0	0	0	0	78	27	78	27
8	MT	86	3	3	0	0	66	77	69	80
4	NC⁽²⁾	264	12	5	0	0	42	16	54	20
8	ND⁽³⁾	29	1	3	0	0	0	0	1	3
7	NE	266	19	7	0	0	156	59	175	66
1	NH	13	0	0	7	54	2	15	9	69
2	NJ^(3),(7)	141	3	2	23	16	28	20	54	38
6	NM	37	0	0	1	3	4	11	5	14
9	NV	7	1	14	0	0	3	43	4	57
2	NY	388	62	16	57	15	33	9	152	39
5	OH	1,083	67	6	91	8	426	39	584	54
6	OK	201	0	0	4	2	0	0	4	2
10	OR	132	1	1	0	0	1	1	2	2
3	PA	672	0	0	2	0	77	11	79	12
2	PR⁽⁴⁾	17	0	0	0	0	0	0	0	0
1	RI	0	0	0	0	0	0	0	0	0
4	SC	66	3	5	9	14	21	32	33	50
8	SD	171	6	4	8	5	6	4	20	12
4	TN	299	2	1	7	2	40	13	49	16
6	TX⁽⁸⁾	1,323	3	0	11	1	2	0	16	1
8	UT	32	0	0	0	0	28	88	28	88
3	VA⁽²⁾	255	0	0	0	0	1	0	1	0
2	VI⁽⁴⁾	12	0	0	0	0	0	0	0	0
1	VT⁽³⁾	1	0	0	0	0	0	0	0	0
10	WA⁽³⁾	193	15	8	5	3	96	50	116	60
5	WI	467	1	0	11	2	0	0	12	3
3	WV	239	0	0	0	0	60	25	60	25
8	WY⁽³⁾	57	0	0	1	2	13	23	14	25
Total		12,440	320	3	608	5	2,065	17	2,993	24

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