Section 809.569. Treatment technique for control of disinfection byproduct (DBP) precursors.

  For public water systems using conventional treatment which are supplied by a surface water source or by a groundwater source under the direct influence of surface water, the department identifies enhanced coagulation or enhanced softening as treatment techniques to control the level of disinfection byproduct precursors in drinking water and distribution systems. Treatment technique requirements for DBP precursors shall comply with the following:

(1)   Enhanced coagulation and enhanced softening performance requirements.

(a) Public water systems using enhanced coagulation or enhanced softening shall achieve the percent reduction of TOC specified in par. (b) between the source water and the combined filter effluent, unless the department approves the water supplier's request for alternate minimum TOC removal (Step 2) requirements under par. (c) .

(b) Required Step 1 TOC reductions, indicated in Table V, are based upon specified source water parameters measured in accordance with s. NR 809.563 (6) . Public water systems practicing softening are required to meet the Step 1 TOC reductions in the far-right column, source water alkalinity >120 mg/L, for the specified source water TOC:

Table V

Step 1 Required Removal of TOC by Enhanced Coagulation and Enhanced Softening for Surface Water Systems Using Conventional Treatment - See PDF for table

1. Public water systems meeting at least one of the conditions in sub. (2) (b) 1. to 7. are not required to operate with enhanced coagulation.

2. Softening treatment systems meeting one of the alternative compliance criteria in sub. (2) (c) are not required to operate with enhanced softening.

3. Public water systems practicing softening shall meet the TOC removal requirements in the column marked >120 for source water alkalinity in mg/L as CaCO 3 .

(c) Water supplier for public water systems using conventional treatment which are supplied by a surface water source or by a groundwater source under the direct influence of surface water which cannot achieve the Step 1 TOC removals required by par. (b) due to water quality parameters or operational constraints shall apply to the department, within 3 months of failure to achieve the TOC removals required by par. (b) , for approval of alternative minimum TOC (Step 2) removal requirements submitted by the water supplier. If the department approves the alternative minimum TOC removal (Step 2) requirements, the department may make those requirements retroactive for the purposes of determining compliance. Until the department approves the alternative minimum TOC removal (Step 2) requirements, the public water system shall meet the Step 1 TOC removals contained in par. (b) .

(d) Applications made to the department by the water supplier for enhanced coagulation treatment systems for approval of alternative minimum TOC removal (Step 2) requirements under par. (c) shall include, as a minimum, results of bench- or pilot-scale testing conducted under subd. 1. and used to determine the alternate enhanced coagulation level.

1. Alternate enhanced coagulation level shall be determined to be coagulation at a coagulant dose and pH as determined by the method described in this subdivision and subds. 2. to 5. such that an incremental addition of 10 mg/L of alum, or equivalent amount of ferric salt, results in a TOC removal of < 0.3 mg/ L. The percent removal of TOC at this point on the "TOC removal versus coagulant dose'' curve shall be determined to be the minimum TOC removal required for the public water system. Once approved by the department, this minimum requirement supersedes the minimum TOC removal required by the table in par. (b) . This requirement will be effective until the department approves a new value based on the results of a new bench- and pilot-scale test. Failure to achieve department-set alternative minimum TOC removal levels is a violation of this chapter and the federal national primary drinking water regulations.

2. Bench- or pilot-scale testing of enhanced coagulation shall be conducted by using representative water samples and adding 10 mg/L increments of alum, or equivalent amounts of ferric salt, until the pH is reduced to a level less than or equal to the enhanced coagulation Step 2 target pH shown in Table W:

Table W

Enhanced Coagulation Step 2 Target pH

Alkalinity (mg/L as CaCO 3 )   Target pH

0-60   5.5

>60-120   6.3

>120-240   7.0

>240   7.5

3. For waters with alkalinity of less than 60 mg/L for which addition of small amounts of alum or equivalent addition of iron coagulant drives the pH below 5.5 before significant TOC removal occurs, the public water system shall add necessary chemicals to maintain the pH between 5.3 and 5.7 in samples until the TOC removal of 0.3 mg/L per 10 mg/L alum added, or equivalent addition of iron coagulant, is reached.

4. The public water system may be operated at any coagulant dose or pH necessary, consistent with other national public drinking water rules or NPDWRs, to achieve the minimum TOC percent removal approved under par. (c) .

5. If the TOC removal is consistently less than 0.3 mg/L of TOC per 10 mg/L of incremental alum dose at all dosages of alum, or equivalent addition of iron coagulant, the water is deemed to contain TOC not amenable to enhanced coagulation. The water supplier may then apply to the department for a waiver of enhanced coagulation requirements.

(2)   Conventional filtration treatment.

(a) Public water systems using conventional filtration treatment which are supplied by a surface water source or by a groundwater source under the direct influence of surface water shall operate with enhanced coagulation or enhanced softening to achieve the TOC percent removal levels specified in sub. (1) unless the public water system meets at least one of the alternative compliance criteria listed in par. (b) or (c) .

(b) Public water systems using conventional filtration treatment which are supplied by a surface water source or by a groundwater source under the direct influence of surface water may use the alternative compliance criteria in subds. 1. to 7. to comply with this section in lieu of complying with sub. (1) . Public water systems shall still comply with monitoring requirements in s. NR 809.565 (5) .

1. The public water system's source water TOC level, measured according to s. NR 809.563 (6) (c) , is less than 2.0 mg/L, calculated quarterly as a running annual average.

2. The public water system's treated water TOC level, measured according to s. NR 809.563 (6) (c) , is less than 2.0 mg/L, calculated quarterly as a running annual average.

3. The public water public water system's source water TOC level, measured as required by s. NR 809.563 (6) (c) , is less than 4.0 mg/L, calculated quarterly as a running annual average; the source water alkalinity, measured according to s. NR 809.563 (6) (a) , is greater than 60 mg/L (as CaCO 3 ), calculated quarterly as a running annual average; and either the TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively; or prior to the effective date for compliance in s. NR 809.562 (2) , the water supplier for the public water system has made a clear and irrevocable financial commitment not later than the effective date for compliance in s. NR 809.562 (2) to use technologies that will limit the levels of TTHMs and HAA5 to no more than 0.040 mg/L and 0.030 mg/L, respectively.

4. Water suppliers shall submit evidence of a clear and irrevocable financial commitment, in addition to a schedule containing milestones and periodic progress reports for installation and operation of appropriate technologies, to the department for approval not later than the effective date for compliance in s. NR 809.562 (2) .

a. These technologies shall be installed and operating not later than June 30, 2005.

b. Failure to install and operate these technologies by the date in the approved schedule shall constitute a violation of this chapter and the national primary drinking water regulations.

5. The TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively, and the public water system uses only chlorine for primary disinfection and maintenance of a residual in the distribution system.

6. The public water system's source water SUVA, prior to any treatment and measured monthly according to s. NR 809.563 (6) (d) , is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.

7. The public water system's finished water SUVA, measured monthly according to s. NR 809.563 (6) (d) , is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.

(c) Public water systems practicing enhanced softening that cannot achieve the TOC removals required by sub. (1) (b) may use the alternative compliance criteria in subds. 1. and 2. in lieu of complying with sub. (1) (b) . Public water systems shall still comply with monitoring requirements in s. NR 809.565 (5) .

1. Softening that results in lowering the treated water alkalinity to less than 60 mg/L (as CaCO 3 ), measured monthly according to s. NR 809.563 (6) (a) and calculated quarterly as a running annual average.

2. Softening that results in removing at least 10 mg/L of magnesium hardness (as CaCO 3 ), measured monthly according to s. NR 809.113 Table A and calculated quarterly as an annual running average.

(3)   Compliance calculations.

(a) Public water systems which are supplied by a surface water source or by a groundwater source under the direct influence of surface water, other than those identified in sub. (2) (b) or (c) shall comply with requirements contained in sub. (1) (b) or (c) . Water suppliers shall calculate compliance quarterly, beginning after the water supplier for the public water system has collected 12 months of data, by determining an annual average using the following method:

1. Determine actual monthly TOC percent removal, by using the following equation: (1-(treated water TOC/source water TOC)) x 100 = percent TOC removal.

2. Determine the required monthly TOC percent removal from either the table in sub. (1) (b) or from sub. (1) (c) .

3. Divide the value in subd. 1. by the value in subd. 2.

4. Add together the results of subd. 3. for the last 12 months and divide by 12.

5. If the value calculated in subd. 4. is less than 1.00, the public water system is not in compliance with the TOC percent removal requirements.

(b) Water supplier may use the provisions in subds. 1. to 5. in lieu of the calculations in par. (a) 1. to 5. to determine compliance with TOC percent removal requirements.

1. In any month that the public water system's treated or source water TOC level, measured according to s. NR 809.563 (6) (c) , is less than 2.0 mg/L, the water supplier may assign a monthly value of 1.0, in lieu of the value calculated in par. (a) 3. when calculating compliance under the provisions of par. (a) .

2. In any month that a public water system practicing softening removes at least 10 mg/L of magnesium hardness as CaCO 3 , the water supplier may assign a monthly value of 1.0 in lieu of the value calculated in par. (a) 3. when calculating compliance under the provisions of par. (a) .

3. In any month that the public water system's source water SUVA, prior to any treatment and measured according to s. NR 809.563 (6) (d) , is < 2.0 L/mg-M, the water supplier may assign a monthly value of 1.0, in lieu of the value calculated in par. (a) 3. when calculating compliance under the provisions of par. (a) .

4. In any month that the public water system's finished water SUVA, measured according to s. NR 809.563 (6) (d) , is < 2.0 L/mg-M, the water supplier may assign a monthly value of 1.0 in lieu of the value calculated in par. (a) 3. when calculating compliance under the provisions of par. (a) .

5. In any month that a public water system practicing enhanced softening lowers alkalinity below 60 mg/L as CaCO 3 , the water supplier may assign a monthly value of 1.0, in lieu of the value calculated in par. (a) 3. when calculating compliance under the provisions of par. (a) .

(c) Public water systems which are supplied by a surface water source or by a groundwater source under the direct influence of surface water and which are using conventional filtration treatment may also comply with the requirements by meeting the criteria in sub. (2) (b) or (c) .

CR 09-073 : cr. Register November 2010 No. 659 , eff. 12-1-10; CR 15-049 : am. (1) (b) Table V, 3., (2) (c) 2. Register March 2016 No. 723 , eff. 4-1-16.