South Carolina Code of Regulations › Chapter 61 - DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROL › Subchapter 61-58.10 - Filtration and Disinfection › Section 61-58.10.D - Disinfection

Current through Register Vol. 48, No. 6, June 28, 2024
A public water system that uses a surface water source and does
				not provide filtration treatment shall provide the disinfection treatment
				specified in paragraph (1) of this section beginning December 30, 1991, unless
				the Department determines, in writing, that filtration is required. A public
				water system that uses a ground water source under the direct influence of
				surface water and does not provide filtration treatment shall provide
				disinfection treatment specified in paragraph (1) of this section beginning
				December 30, 1991, or 18 months after the Department determines that the ground
				water source is under the influence of surface water, whichever is later,
				unless the Department has determined, in writing, that filtration is required.
				If the Department has determined that filtration is required, the system shall
				comply with any interim disinfection requirements the Department deems
				necessary before filtration is installed. A system that uses a surface water
				source that provides filtration treatment shall provide the disinfection
				treatment specified in paragraph (2) of this section beginning June 29, 1993,
				or beginning when filtration is installed, whichever is later. A system that
				uses a ground water source under the direct influence of surface water and
				provides filtration treatment shall provide disinfection treatment as specified
				in paragraph (2) of this section by June 29, 1993, or beginning when filtration
				is installed, whichever is later. Failure to meet any requirement of this
				section after the applicable date specified in this introductory paragraph is a
				treatment technique violation.
(1)
			 Disinfection requirements for public water systems that do not provide
			 filtration.
Each public water system that does not provide filtration
				treatment shall provide disinfection treatment as follows:
(a) The disinfection treatment shall be
			 sufficient to ensure at least 99.9 percent (3-log) inactivation of Giardia
			 lamblia cysts and 99.99 percent (4-log) inactivation of viruses, every day the
			 system serves water to the public, except any one day each month. Each day a
			 system serves water to the public, the public water system shall calculate the
			 CT value(s) from the system's treatment parameters, using the procedure
			 specified in R.61-58.10(F)(2)(c)(F)(2)(c),
			 and determine whether this value(s) is sufficient to achieve the specified
			 inactivation rates for Giardia lamblia cysts and viruses. If a system uses a
			 disinfectant other than chlorine, the system may demonstrate to the Department,
			 through the use of a Department-approved protocol for on-site disinfection
			 challenge studies or other information satisfactory to the Department, that
			 CT99.9 values other than those specified in Tables 2.1
			 and 3.1 in R.61-58.10(F)(2)(c)(F)(2)(c) or other operational parameters are
			 adequate to demonstrate that the system is achieving minimum inactivation rates
			 required by paragraph (1)(a) of this section.
(b) The disinfection system shall have
			 either:
(i) redundant components, including
			 an auxiliary power supply with automatic start-up and alarm to ensure that
			 disinfectant application is maintained continuously while water is being
			 delivered to the distribution system, or
(ii) automatic shut-off of delivery of water
			 to the distribution system whenever there is less than 0.2 mg/l of residual
			 disinfectant concentration in the water. If the Department determines that
			 automatic shut-off would cause unreasonable risk to health or interfere with
			 fire protection, the system shall comply with paragraph (1)(b)(i) of this
			 section.
(c) The
			 residual disinfectant concentration in the water entering the distribution
			 system, measured as specified in R.61-58.10(F)(1)(e) and (2)(e)(F)(1)(e) and
			 (2)(e), cannot be less than 0.2 mg/l for more
			 than 4 hours.
(d)
(i) The residual disinfectant concentration
			 in the distribution system, measured as total chlorine, combined chlorine, or
			 chlorine dioxide, as specified in R.61-58.10(F)(1)(c)(F)(1)(e) and
			 (2)(f), cannot be undetectable in more than 5
			 percent of the samples each month, for any two consecutive months that the
			 system serves water to the public. Water in the distribution system with a
			 heterotrophic bacteria concentration less than or equal to 500/ml, measured as
			 heterotrophic plate count (HPC) as specified in R.61-58.10(F)(1)(e) and
			 (2)(f)(F)(1)(c), is deemed to have a
			 detectable disinfectant residual for purposes of determining compliance with
			 this requirement. Thus, the value "V" in the following formula cannot exceed 5
			 percent in one month, for any two consecutive months.
V = c + d + e X 100 / a + b
where:
a = number of instances where the residual disinfectant
				concentration is measured;
b = number of instances where the residual disinfectant
				concentration is not measured but heterotrophic bacteria plate count (HPC) is
				measured;
c = number of instances where the residual disinfectant
				concentration is measured but not detected and no HPC is measured;
d = number of instances where the residual disinfectant
				concentration is measured but not detected and where the HPC is > 500/ml;
				and
e = number of instances where the residual disinfectant
				concentration is not measured and HPC is > 500/ml.
(ii) If the Department determines, based on
			 site-specific considerations, that a system has no means for having a sample
			 transported and analyzed for HPC by a certified laboratory under the requisite
			 time and temperature conditions specified by R.61-58.10(F)(1)(c)(F)(1)(c)
			 and that the system is providing adequate disinfection in the distribution
			 system, the requirements of paragraph (1)(d)(i) of this section do not apply to
			 that system.