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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.

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

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 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

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 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

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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