18 AAC 80.635. General disinfection requirements

(a) Failure to meet a requirement of this section, 18 AAC 80.640, or 18 AAC 645 after the applicable date specified in this subsection or in (b) of this section is a treatment technique violation.

(b) The owner or operator of a Class A or Class B public water system using a surface water source or a GWUDISW source and providing filtration treatment shall provide the disinfection treatment specified in (c) of this section and 18 AAC 80.645 beginning when filtration is installed.

(c) If the department or the EPA has not determined in writing that filtration is required, the owner or operator of a Class A or Class B public water system that does not provide filtration treatment shall provide the disinfection treatment described in 18 AAC 80.640 as follows:

(1) for a new system using a surface water source, the disinfection treatment requirements of this subsection apply within 18 months after the department signs the final approval portion of the construction and operation certificate for the system under 18 AAC 80.210(k) ; or

(2) for a system using a GWUDISW source, the disinfection treatment requirements of this subsection apply within six months after the department determines that the groundwater source is under the direct influence of surface water; within 18 months after the department determines that the groundwater source is under the direct influence of surface water, the owner or operator shall provide disinfection treatment as described in 18 AAC 80.640;

(3) the residual disinfectant concentration in the water entering the distribution system, measured as described in 18 AAC 80.340(d) (2) and 18 AAC 80.655(b) and (c), may not be less than 0.2 mg/l for more than four hours;

(4) the residual disinfectant concentration in the distribution system, measured as required by 18 AAC 80.340(d) (2) and 18 AAC 80.655(d) , may not be undetectable in more than five percent of the samples each month for any two consecutive months during which the system serves water to the public; heterotrophic bacteria, measured as heterotrophic plate count (HPC) under 18 AAC 80.1100(k), may be measured instead of residual disinfectant concentration; water in the distribution system with a heterotrophic bacteria density less than or equal to 500 per ml, measured as HPC as specified in 18 AAC 80.1100(k) is considered to have a detectable disinfectant residual for purposes of determining compliance with this paragraph; the value "V" in the following formula may not exceed five percent in one month, for any two consecutive months:

V (in percent) = c + d + e --------- a + b x 100

where:

a = the number of samples where the residual disinfectant concentration is measured;

b = the number of samples where the residual disinfectant concentration is not measured, but (HPC) is measured;

c = the number of samples where the residual disinfectant concentration is measured but not detected, and HPC is not measured;

d = the number of samples where residual disinfectant concentration is measured but not detected, and where the HPC is greater than 500 per ml; and

e = the number of samples where the residual disinfectant concentration is not measured and HPC is greater than 500 per ml;

(5) the requirements of (4) of this subsection, 18 AAC 80.655(d) , and 18 AAC 80.670(a) (3) do not apply to the public water system if the department determines, based on site-specific considerations, that

(A) the owner or operator lacks a means for having a sample transported and analyzed for HPC by a certified laboratory under the time and temperature conditions required by 40 C.F.R. 141.74(a), adopted by reference in 18 AAC 80.010(a) ; and

(B) the system provides adequate disinfection in the distribution system;

(6) the owner or operator who routinely uses HPC measurements instead of distribution system disinfectant residual measurements shall notify the department if the circumstance described in (5)(A) of this subsection prevents HPC sample analysis; a notification must include

(A) a description of how the owner or operator routinely has HPC samples analyzed;

(B) the specific reason a sample cannot be analyzed as required;

(C) a proposed disinfectant residual measurement or other plan to be used to confirm adequate disinfection in the distribution system;

(D) a summary of disinfectant concentrations entering the distribution system; and

(E) system coliform results for the preceding month;

(7) the department will confirm that the circumstance described in (5)(A) of this subsection prevents HPC sample analysis and will specify an alternate method to assure adequate system disinfection by adopting or modifying the proposal submitted by the owner or operator or specifying another method;

(8) an alternate method of assuring adequate disinfection in the absence of HPC samples will usually involve monitoring system disinfection levels as prescribed by 18 AAC 80.600 - 18 AAC 80.680 and 18 AAC 80.699;

(9) if the circumstance described in (5)(A) of this subsection prevents HPC analysis for more than five percent of the required samples in any one-year period, the department will disallow the HPC method and require monitoring of system disinfectant concentrations, if disallowing the HPC method and requiring monitoring serves the interests of public health; the department will notify the owner or operator of a decision to disallow the HPC method.

(d) If the department or the EPA has determined in writing that filtration is required, the owner or operator of the system shall comply with interim disinfection requirements that the department considers necessary before filtration is installed. In determining interim disinfection requirements for a public water system that requires filtration, the department will

(1) require the owner or operator to provide

(A) historical disease outbreak data;

(B) the size of the population served by the system;

(D) water quality data; and

(E) operation and maintenance specifications on the disinfection unit used;

(2) determine interim treatment requirements on a case-by-case basis; the minimum interim treatment requirement is disinfection; as additional interim requirements, the department will require

(A) additional disinfection or "boil water" notices if evidence of an acute MCL violation exists; or

(B) use of a different source water, as the department determines necessary to serve the interests of public health;

(3) as the department determines necessary to serve the interests of public health, require either additional disinfection and monitoring or evidence of the reliability of current treatment techniques if

(A) a coliform MCL violation occurs;

(B) a waterborne disease outbreak occurs; or

(4) allow HPC instead of residual disinfectant concentration as an indicator of adequate disinfection, if the department determines that allowing HPC as an indicator serves the interests of public health; and

(5) set a schedule of implementation by the owner or operator.

History: Eff. 10/1/99, Register 151

Authority: AS 46.03.020

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