18 AAC 80.640. Disinfection requirements for systems avoiding filtration

(a) In addition to the requirements of 18 AAC 80.635(c) , the owner or operator of a Class A or Class B public water system that does not provide filtration treatment shall provide disinfection treatment as follows:

(1) the disinfection treatment must 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 each day the system serves water to the public, except any one day each month; each day a system serves water to the public, the owner or operator of the system shall calculate the CT value from the system's treatment parameters using the procedure described in 18 AAC 80.660(f) - (h) and determine whether the CT value is sufficient to achieve the specified inactivation rates for Giardia lamblia cysts and viruses;

(2) the disinfection system must have

(A) redundant components, including a backup power supply with automatic startup and alarm or other means approved by the department that will ensure that disinfectant application is maintained continuously while water is being delivered to the distribution system; or

(B) automatic shutoff of delivery of water to the distribution system.

(b) The department will allow automatic shutoff under (a)(2)(B) of this section if

(1) the water entering the distribution system contains less than 0.2 mg/l of residual disinfectant concentration;

(2) the department's evaluation of the public water system configuration confirms adequate protection against negative pressures in the system;

(3) provisions exist for high demand periods including fire flow requirements;

(4) the department's evaluation of the public water system confirms that the system has adequate distribution system storage to maintain positive pressure of at least 20 pounds per square inch for continued water use; and

(5) the department finds that automatic shutoff does not cause unreasonable risk to health or interfere with fire protection.

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

Authority: AS 46.03.020

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