Section NR 809.561 - Maximum residual disinfectant level goals (MRDLGs), and maximum contaminant levels (MCLs) for disinfection byproducts, maximum residual disinfectant levels (MRDLs) and best available treatment(1) MAXIMUM RESIDUAL DISINFECTANT LEVEL GOALS. MRDLGs for disinfectants are as follows: Disinfectant residual | MRDLG (mg/L) |
Chlorine ........................ | 4 (as Cl2) |
Chloramines ..................... | 4 (as Cl2) |
Chlorine dioxide .................. | 0.8 (as ClO2) |
(2) MAXIMUM CONTAMINANT LEVELS. The maximum contaminant levels (MCLs) for disinfection byproducts are as follows: Disinfection byproduct | MCL (mg/L) |
Total trihalomethanes (TTHM) ..... | 0.080 |
Haloacetic acids (five) (HAA5) ..... | 0.060 |
Bromate ................ | 0.010 |
Chlorite ................ | 1.0 |
(3) MAXIMUM RESIDUAL DISINFECTANT LEVELS. (a) The maximum residual disinfectant levels (MRDLs) for disinfectants are as follows: Residual Disinfectants | MRDL (mg/L) |
Chlorine ...................... | 4.0 (as C12) |
Chloramines ................... | 4.0 (as C12) |
Chlorine dioxide ................ | 0.8 (as ClO2) |
(b) To achieve compliance with the maximum residual disinfectant levels identified in this subsection, water suppliers shall control treatment processes by reducing disinfectant demand and by controlling disinfection treatment processes to reduce disinfectant levels.(c) Free chlorine or total chlorine may be measured for demonstrating compliance with the chlorine MRDL. Combined chlorine or total chlorine may be used for demonstrating compliance with the chloramine MRDL.(4) BEST AVAILABLE TREATMENT. The department, pursuant to section 1412 of the Safe Drinking Water Act and related regulations applicable to public water systems, identifies the following as the best available treatment technology, treatment techniques or other means available for achieving compliance with the maximum contaminant levels for disinfection byproducts identified in sub. (1): Disinfectant byproduct | Best available treatment |
TTHM and HAA5 | Enhanced coagulation or enhanced softening or GAC10, with chlorine as the primary and residual disinfectant. Enhanced coagulation or enhanced softening, plus GAC10; or nanofiltration with a molecular weight cutoff = 1000 Daltons; or GAC20. |
TTHM and HAA5 in Consecutive Systems | Systems serving = 10,000: Improved distribution system and storage tank management to reduce residence time, plus the use of chloramines for disinfectant residual maintenance. Systems serving < 10,000: Improved distribution system and storage tank management to reduce residence time. |
Bromate | Control of ozone treatment process to reduce production of bromate. |
Chlorite | Control of treatment processes to reduce disinfectant demand and control of disinfection treatment processes to reduce disinfectant levels. |
(5) ALTERNATIVE TREATMENT. The department may approve the use of alternative treatment not listed in sub. (4), if a water supplier demonstrates to the department, using pilot studies or other means, that the alternative treatment is sufficient to achieve compliance with the MCLs in sub. (2).Wis. Admin. Code Department of Natural Resources § NR 809.561
CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.Amended by, CR 15-049: cr. (3) (c), am. (4) Register March 2016 No. 723, eff.4/1/2016