NR 809.569NR 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:

NR 809.569(1)(a)(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).

NR 809.569(1)(b)(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:

NR 809.569(1)(b)1.1. 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.

NR 809.569(1)(b)2.2. Softening treatment systems meeting one of the alternative compliance criteria in sub. (2) (c) are not required to operate with enhanced softening.

NR 809.569(1)(b)3.3. Public water systems practicing softening shall meet the TOC removal requirements in the column marked >120 for source water alkalinity in mg/L as CaCO3.

NR 809.569(1)(c)(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).

NR 809.569(1)(d)(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.

NR 809.569(1)(d)1.1. 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.

NR 809.569(1)(d)2.2. 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:

NR 809.569(1)(d)3.3. 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.

NR 809.569(1)(d)4.4. 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).

NR 809.569(1)(d)5.5. 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.

NR 809.569(2)(a)(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).

NR 809.569(2)(b)(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).