Rule 3745-81-11 | Maximum contaminant levels and best available technologies for inorganic contaminants.
(A) The following maximum contaminant levels (MCLs) for inorganic contaminants apply to all public water systems.
| Contaminant | MCL in milligrams per liter |
| Nitrate (as nitrogen) | 10 |
| Nitrite (as nitrogen) | 1 |
| Total nitrate and nitrite (as nitrogen) | 10 |
(B) The following MCLs for inorganic contaminants apply to all community and nontransient noncommunity public water systems.
| Contaminant | MCL in milligrams per liter |
| Antimony | 0.006 |
| Arsenic | 0.010 |
| Asbestos | 7a |
| Barium | 2 |
| Beryllium | 0.004 |
| Cadmium | 0.005 |
| Chromium | 0.1 |
| Cyanide (as free cyanide) | 0.2 |
| Fluoride | 4.0 |
| Mercury | 0.002 |
| Selenium | 0.05 |
| Thallium | 0.002 |
| a. In units of millions of fibers per liter, where only fibers longer than ten micrometers are counted. |
(C) The following MCL for bromate applies to all community and nontransient noncommunity public water systems that treat their water with ozone.
| Contaminant | MCL in milligrams per liter |
| Bromate | 0.010 |
(D) The following MCL for chlorite applies to all community and nontransient noncommunity public water systems that treat their water with chlorine dioxide.
| Contaminant | MCL in milligrams per liter |
| Chlorite | 1.0 |
(E) The director may require a public water system to apply best available technology in order to reduce the level of a contaminant to below its MCL. The director identifies the following as the best available technologies (BATs) for removal of the following inorganic contaminants from water.
| Contaminant | BATs |
| Antimony | 2,7 |
| Arsenica | 1, 2, 5, 6, 7, 9, 12b |
| Asbestos | 2, 3, 8 |
| Barium | 5, 6, 7, 9 |
| Beryllium | 1, 2, 5, 6, 7 |
| Bromate | 14 |
| Cadmium | 2, 5, 6, 7 |
| Chlorite | 15 |
| Chromium | 2, 5, 6c, |
| Cyanide | 5, 7, 13 |
| Mercury | 2d, 4, 6d, 7d |
| Nitrate | 5, 7, 9 |
| Nitrite | 5, 7 |
| Selenium | 1, 2e, 6, 7, 9 |
| Thallium | 1, 5 |
| a. BATs for arsenic (V). Pre-oxidation may be required to convert arsenic (III) to arsenic (V) | |
| b. To obtain high removals the iron to arsenic ratio must be at least 20:1 | |
| c. BAT for chromium (III) only | |
| d. BAT only for mercury concentrations of ten micrograms per liter or less | |
| e. BAT for selenium (IV) only | |
| Key to BATs in table: | |
| 1 = Activated alumina | |
| 2 = Coagulation/filtration (not BAT for systems 500 service connections) | |
| 3 = Direct filtration | |
| 4 = Granular activated carbon | |
| 5 = Ion exchange | |
| 6 = Lime softening (not BAT for systems 500 service connections) | |
| 7 = Reverse osmosis | |
| 8 = Corrosion control | |
| 9 = Electrodialysis | |
| 10 = Chlorine | |
| 11 = Ultraviolet | |
| 12 = Oxidation/filtration | |
| 13 = Alkaline chlorination (pH >8.5) | |
| 14 = Control of ozone treatment process to reduce production of bromate | |
| 15 = Control of treatment processes to reduce disinfectant demand and control of disinfectant treatment processes to reduce disinfectant levels |
Last updated October 31, 2024 at 8:40 AM
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