NAC445A.6683. Disinfection of water: Chlorination.

If chlorine is used for the disinfection of water:

     1. The disinfection must be accomplished with liquefied or gaseous chlorine, calcium hypochlorite or sodium hypochlorite.

     2. The supplier of water shall use chlorinators that:

     (a) Feed chlorine into solution by gas or feed hypochlorite by positive displacement or erosion;

     (b) Are determined to be compatible with drinking water; and

     (c) Are designed in a manner which ensures that a chlorine residual of not less than 0.05 mg/l is maintained at all times and at all locations in the distribution system.

     3. The supplier of water shall provide and maintain a kit of spare parts for all chlorinators which is adequate for the repair of any parts that are subject to wear and breakage. If the supplier of water does not have the ability to repair chlorinators in an expeditious manner, he or she must provide a complete backup set of equipment for chlorination.

     4. The application of chlorine must be by automatic control, except that manual control may be used where a system for chlorination only treats water of reasonably constant flow and quality. If the application of chlorine is by automatic control:

     (a) Flow proportional control must be used where the quality of the water is reasonably constant and the rate of flow is not reasonably constant; and

     (b) Residual flow control must be used under other conditions.

     5. The chlorine must be applied:

     (a) Continuously at a point in such a manner that, based on the pH, temperature and biological quality of the water, the presence in the water of any ammonia or substances that produce taste or odor, and any other pertinent factors, will provide for the maximum period of contact and maximum mixing. Where necessary, appropriate baffles or methods of blending must be provided.

     (b) In a manner that minimizes the formation of chloro-organic compounds that are significant to the public health.

     (c) If groundwater is being treated, by applying the chlorine at the wellhead, an inlet for a storage tank or a pipeline in a manner that will provide an adequate period of contact to inactivate enteric viruses and kill bacteria, parasites and other pathogens.

     6. The piping for chlorinators must be designed in such a manner as to prevent contamination of the supply of treated water by water of uncertain or nonpotable quality. Unless otherwise approved by the Division or the appropriate district board of health, only finished water may be used in a chlorinator.

     7. The supplier of water shall:

     (a) Provide equipment for testing chlorine residual which is capable of:

          (1) Performing the procedures identified in Standard Methods for the Examination of Water and Wastewater, as adopted by reference in NAC 445A.6663; and

          (2) Measuring chlorine residual to the nearest 0.05 mg/l or 0.05 ppm.

     (b) If surface water is chlorinated, provide automatic recorders of chlorine residual.

     (Added to NAC by Bd. of Health, eff. 2-20-97; A by Environmental Comm’n by R194-08, 10-27-2009)