Statutes, codes, and regulations
Wisconsin Administrative Code
Agency - Department of Natural ResourcesEnvironmental Protection - Water SupplyChapter NR 809 - Safe Drinking Water
Subchapter I - Maximum Contaminant Levels, Monitoring and Analytical Requirements for Primary Drinking Water Contaminants
Section NR 809.11 - Inorganic chemical maximum contaminant levels and BATs

Wis. Admin. Code Department of Natural Resources NR 809.11

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Current through November 25, 2024
Section NR 809.11 - Inorganic chemical maximum contaminant levels and BATs
(1) APPLICABILITY. The following requirements apply to all of the maximum contaminant levels for inorganic contaminants:
(a) The maximum contaminant levels for nitrate and nitrite apply to both community water systems and non-community water systems, except as provided in sub. (3).
(b) The maximum contaminant level for fluoride only applies to community water systems.
(c) The maximum contaminant levels for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, mercury, nickel, selenium and thallium apply to community water systems and non-transient, non-community water systems.
(d) Compliance with maximum contaminant levels for inorganic chemicals is calculated under s. NR 809.117.
(2) MCLS FOR INORGANICS. The following are the maximum contaminant levels for inorganic contaminants:

Contaminant

MCL in mg/ L

Antimony

0.006

Arsenic

0.010

Asbestos

7 Million fibers/Liter

(longer than 10 um)

Barium

2

Beryllium

0.004

Cadmium

0.005

Chromium

0.1

Cyanide(as free Cyanide)0.2

Fluoride

4.0

Mercury

0.002

Nickel

0.1

Nitrate

10 (as Nitrogen)

Nitrite

1 (as Nitrogen)

Total Nitrate Nitrite

10 (as Nitrogen)

Selenium

0.05

Thallium

0.002

(3) OPERATION WITH NITRATES NOT EXCEEDING 20 MG/L. At the discretion of the department, nitrate as nitrogen levels not to exceed 20 mg/l may be allowed in a non-community water system if the water supplier demonstrates all of the following to the satisfaction of the department:
(a) The water will not be available to children under 6 months of age or any female who is or may become pregnant.
(b) The water supplier meets the public notification requirements under s. NR 809.958, including continuous posting of the fact that nitrate as nitrogen levels exceed 10 mg/l and the potential health effects of exposure.
(c) Local and state public health authorities will be notified annually of nitrate as nitrogen levels that exceed 10 mg/l.
(d) A supply of bacteriologically safe drinking water, containing less than 10 mg/l nitrate as nitrogen, is provided for infants less than 6 months of age and any female who is or may become pregnant.
(e) No adverse health effects will result.
(4) BEST AVAILABLE TREATMENT. The best available treatment technologies for inorganic contaminants are as follows:
(a) The best available technologies or BATs for achieving compliance with the maximum contaminant levels for the inorganic contaminants listed in sub. (2), except for fluoride, are as follows:

Contaminant

BAT(s)

Antimony

2,7

Arsenic4

1,2,5,6,7,9,125

Asbestos

2,3,8

Barium

5,6,7,9

Beryllium

1,2,5,6,7

Cadmium

2,5,6,7

Chromium

2,5,62,7

Cyanide

5,7,10,13

Mercury

21,4,61,71

Nickel

5,6,7

Nitrate

5,7,9

Nitrite

5,7

Selenium

1,23,6,7,9

Thallium

1,5

1 BAT only if influent Hg concentration.

2 BAT for Chromium III only.

3 BAT for Selenium IV only.

4 BATs for Arsenic V. Pre-oxidation may be required to convert Arsenic III to Arsenic V.

5 To obtain high removals, iron to arsenic ratio mus be at least 20:1.

Key to BATs in Table:

1 = Activated Alumina

2 = Coagulation/Filtration (not BAT for public water systems < 500 service connections)

3 = Direct and Diatomite Filtration

4 = Granular Activated Carbon

5 = Ion Exchange

6 = Lime Softening (not BAT for public water systems < 500 service connections)

7 = Reverse Osmosis

8 = Corrosion Control

9 = Electrodialysis

10 = Oxidation (Chlorine)

11 = Ultraviolet

12 = Oxidation/Filtration

13 = Alkaline Chlorination (pH >= 8.5)

(b) A water supplier may use an alternative treatment not listed in par. (a) if it is demonstrated to the department, using pilot studies or other means, that the alternative treatment is sufficient to achieve compliance with the MCLs in sub. (2).
(5) SMALL WATER SYSTEM COMPLIANCE TECHNOLOGIES FOR ARSENIC.
(a) The EPA identifies the following table as the affordable technology, treatment technique, or other means available to public water systems serving 10,000 persons or fewer for achieving compliance with the maximum contaminant level for arsenic: -

Small Water System Compliance Technologies1 for Arsenic2

Small water system compliance technology

Affordable for listed small water system categories3

Activated Alumina (centralized)

All size categories

Activated Alumina (Point-of-Use)4

All size categories

Coagulation/Filtration5 3,301-10,000

501-3,300,

Coagulation-assisted Microfiltration 3,301-10,000

501-3,300,

Electrodialysis reversal6 3,301-10,000

501-3,300,

Enhanced coagulation/filtration

All size categories

Enhanced lime softening (pH> 10.5)

All size categories

Ion Exchange

All size categories

Lime Softening5 3,301-10,000

501-3,300,

Oxidation/Filtration7

All size categories

Reverse Osmosis (centralized)6 3,301-10,000

501-3,300,

Reverse Osmosis (Point-of-Use)4

All size categories

1 Section 1412(b)(4)(E)(ii) of the Safe Drinking Water Act or SDWA specifies that small water system compliance technologies must be affordable and technically feasible for small systems.

2 Small water system compliance technology for Arsenic V. Pre-oxidation may be required to convert Arsenic III to Arsenic V.

3 Section 1412(b)(4)(E)(ii) of the Safe Drinking Water Act or SDWA specifies 3 categories of small water systems: (i) those serving 25 or more, but fewer than 501, (ii) those serving more than 500, but fewer than 3,301, and (iii) those serving more than 3,300, but fewer than 10,001.

4 When POU or POE devices are used for compliance, programs to ensure proper long-term operation, maintenance, and monitoring must be provided by the water supplier to ensure adequate performance.

5 Unlikely to be installed solely for arsenic removal. May require pH adjustment to optimal range if high removals are needed.

6 Technologies reject a large volume of water-may not be appropriate for areas where water quantity may be an issue.

7 To obtain high removals, iron to arsenic ratio must be at least 20:1.

(b) The department may allow Point of Use (POU) treatment only if the department determines that treatment prior to entry to the distribution system is not feasible.

Wis. Admin. Code Department of Natural Resources NR 809.11

CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.
Amended by, CR 15-049: am. (2), (3) (a), (d), (4) (a) Register March 2016 No. 723, eff.4/1/2016