Wisconsin Administrative Code › Department of Natural Resources › NR 800 - Environmental Protection - Water Supply › Chapter NR 809 - Safe Drinking Water › Subchapter III - Maximum Contaminant Levels, Maximum Residual Disinfectant Levels, Monitoring, Analytical Requirements and Control of Disinfection Byproducts, Disinfection Residuals and Stage 1 and Stage 2 DBP › Section NR 809.569 - Treatment technique for control of disinfection byproduct (DBP) precursors

Current through June 24, 2024
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
Source water TOC, mg/l
Removal of TOC (in percentages) for source water
								  alkalinity concentration ranges(in mg/L) as CaCO3
0 - 60 mg/L
> 60 - 120 mg/L
> 120 mg/L
>2.0-4.0
35.0%
25.0%
15.0%
>4.0-8.0
45.0%
35.0%
25.0%
>8.0
50.0%
40.0%
30.0%
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
								  CaCO3)
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 betwee n 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.