Indiana Administrative Code
Title 327 - WATER POLLUTION CONTROL DIVISION
Article 8 - PUBLIC WATER SUPPLY
Rule 2 - Drinking Water Standards
Section 2-4 - Inorganic chemicals; maximum contaminant levels
Current through September 18, 2024
Authority: IC 13-13-5; IC 13-14-8-7; IC 13-14-9; IC 13-18-3; IC 13-18-16
Affected: IC 13-18
Sec. 4.
(a) The following MCLs for inorganic chemicals apply to all CWSs, NTNCWSs, and TWSs except as provided in subsection (b):
| Contaminant | Level in Milligrams Per Liter |
| Nitrate | 10 (as nitrogen) |
| Nitrite | 1 (as nitrogen) |
| Nitrate and nitrite | 10 (as nitrogen) |
(b) The commissioner may allow nitrate levels up to, but not to exceed, twenty (20) milligrams per liter in a noncommunity water system if the supplier of water meets all of the following conditions:
(c) The following MCL for fluoride applies to all CWSs:
Contaminant Level in Milligrams Per Liter
Fluoride 4.0
(d) The following MCLs for inorganic chemicals apply to all CWSs and NTNCWSs:
| Contaminant | Level in Milligrams Per Liter Except Asbestos |
| Antimony | 0.006 |
| Arsenic | 0.0101 |
| Asbestos | 7 (MFL) 2 |
| Barium | 2 |
| Beryllium | 0.004 |
| Cadmium | 0.005 |
| Chromium | 0.1 |
| Cyanide (free) | 0.2 |
| Mercury | 0.002 |
| Selenium | 0.05 |
| Thallium | 0.002 |
1 Effective January 1, 2006. Until then, the arsenic MCL is 0.05 mg/l.
2MFL = million fibers per liter greater than ten (10) micrometers.
(e) For the inorganic chemicals listed in this section and nickel, the monitoring frequency is specified in section 4.1 of this rule and analytical methods are specified in section 4.2 of this rule.
(f) The commissioner hereby identifies the following as the BAT, treatment technique, or other means available for achieving compliance with the MCLs for inorganic contaminants identified in subsections (a), (c), and (d), except fluoride:
| BAT for Inorganic Chemicals Listed in This Section | |
| Chemical Name | BATs |
| 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 |
| Mercury | 21,4,61,71 |
| Nitrate | 5,7,9 |
| Nitrite | 5,7 |
| Selenium | 1,23,6,7,9 |
| Thallium | 1,5 |
1 BAT only if influent mercury concentrations less than ten (10) micrograms per liter.
2 BAT for Chromium III only.
3 BAT for Selenium IV only.
4 BATs for Arsenic V. Preoxidation may be required to convert Arsenic III to Arsenic V. Arsenic BATs apply beginning January 1, 2006.
5 To obtain high removals, iron to arsenic ratio must be at least 20:1.
Key to BATs in Table
(g) The commissioner, pursuant to Section 1412 of the Act, hereby identifies in the following table the affordable technology, treatment technique, or other means available to systems serving ten thousand (10,000) persons or fewer for achieving compliance with the MCL for arsenic that will be applicable beginning January 1, 2006:
| 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 > 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 the Act specifies that SSCTs must be affordable and technically feasible for small systems.
2SSCTs for Arsenic V. Preoxidation may be required to convert Arsenic III to Arsenic V.
3The Act (ibid.) specifies three (3) categories of small systems as follows:
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.
6Technologies 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.
