Contaminant | MCL (mg/l) |
(1) Fluoride | 4.0 |
(2) Asbestos | 7 Million Fibers/liter (longer than 10 [MICRO]m). |
(3) Barium | 2 |
(4) Cadmium | 0.005 |
(5) Chromium | 0.1 |
(6) Mercury | 0.002 |
(7) Nitrate | 10 (as Nitrogen) |
(8) Nitrite | 1 (as Nitrogen) |
(9) Total Nitrate and Nitrite | 10 (as Nitrogen) |
(10) Selenium | 0.05 |
(11) Antimony | 0.006 |
(12) Beryllium | 0.004 |
(13) Cyanide (as free Cyanide) | 0.2 |
(14) [Reserved] | |
(15) Thallium | 0.002 |
(16) Arsenic | 0.010 |
BAT for Inorganic Compounds Listed in Section 141.62(b)
Chemical Name | 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 | 5,7,13 |
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 concentrations [LESS THAN EQUAL TO]10[MICRO]g/1.
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 must be at least 20:1.
Key to BATS in Table
1 = Activated Alumina
2 = Coagulation/Filtration (not BAT for systems [LESS THAN]500 service connections)
3 = Direct and Diatomite Filtration
4 = Granular Activated Carbon
5 = Ion Exchange
6 = Lime Softening (not BAT for systems [LESS THAN]500 service connections)
7 = Reverse Osmosis
8 = Corrosion Control
9 = Electrodialysis
10 = Chlorine
11 = Ultraviolet
12 = Oxidation/Filtration
13 = Alkaline Chlorination (pH [GREATER THAN EQUAL TO]8.5)
Small System Compliance Technologies (SSCTs)1 for Arsenic2
Small system compliance technology | Affordable for listed small system categories3 |
Activated Alumina (centralized) | All size categories. |
Activated Alumina (Point-of-Use)4 | All size categories. |
Coagulation/Filtration5 | 501-3,300, 3,301-10,000. |
Coagulation-assisted Microfiltration | 501-3,300, 3,301-10,000. |
Electrodialysis reversal6 | 501-3,300, 3,301-10,000. |
Enhanced coagulation/filtration | All size categories |
Enhanced lime softening (pH[GREATER THAN]10.5) | All size categories. |
Ion Exchange | All size categories. |
Lime Softening5 | 501-3,300, 3,301-10,000. |
Oxidation/Filtration7 | All size categories. |
Reverse Osmosis (centralized)6 | 501-3,300, 3,301-10,000. |
Reverse Osmosis (Point-of-Use)4 | All size categories. |
1 Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs must be affordable and technically feasible for small systems.
2 SSCTs for Arsenic V. Pre-oxidation may be required to convert Arsenic III to Arsenic V.
3 The Act (ibid.) specifies three categories of small 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 system 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.
40 C.F.R. §141.62