Look Inside. This standard presents essential procedures for the disinfection of new and repaired potable water mains. Sorry, this item can only be purchased by current members. Topics covered include forms of chlorine disinfection, a description of the disinfection procedure, preventive and corrective measures during construction, methods of chlorination, final Topics covered include forms of chlorine disinfection, a description of the disinfection procedure, preventive and corrective measures during construction, methods of chlorination, final flushing, bacteriological testing, redisinfection, final connections to existing mains, disinfection procedures when cutting into or repairing existing mains, and special procedures for caulked tapping sleeves.
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Some variations from this format may be found in a particular standard. PAGE Foreword 4. A Background B History C Acceptance A Information on Application of New Mains A Purchaser Options and 4. B Modification to Standard This standard describes methods of disinfecting newly constructed potable water mains; mains that have been removed from service for planned repairs or for maintenance that exposes them to contamination; mains that have undergone emergency repairs because of physical failure; and mains that, under normal operation, continue to show the presence of coliform organisms.
The disinfecting agents discussed in this standard are chlorine solutions that may be derived from liquid chlorine Cl2 , calcium hypochlorite Ca OCl 2 , or sodium hypochlorite NaOCl.
Combinations of free chlorine residual and contact time are provided. Chlorine dosage reference tables are provided as appendix B of this standard. This standard was first approved on Sept. Revisions were approved on Sept. This edition was approved on June 8, In the United States, authority to regulate products for use in, or in contact with, drinking water rests with individual states.
Specific policies of the state or local agency. Individual states or local agencies have authority to accept or accredit certification organizations within their jurisdictions.
Accreditation of certi- fication organizations may vary from jurisdiction to jurisdiction. Use of Annex A procedures may not always be identical, depending on the certifier. Thus, users of this standard should consult the appropriate state or local agency having jurisdiction in order to 1.
Determine additives requirements including applicable standards. Determine the status of certifications by parties offering to certify products for contact with, or treatment of, drinking water. Determine current information on product certification. Special Issues. Information on Application of This Standard.
Generally, it is easier to disinfect a new main than one that has had emergency repairs in terms of access, sanitary control, and the time available for disinfection, sampling, and testing.
For a new main, there is typically more time available for disinfection and test- ing since there is no immediate demand from customers. Given the often significant amount of time and materials involved in a new water main project, careful disin- fection and testing of the main are reasonable and necessary to ensure public health protection.
Conditions for pipe repair projects vary tremendously in terms of the size of the repair, the sanitary conditions, and the time constraints resulting from immediate cus- tomer demands. It should be noted if the line is depressurized or opened to the envi- ronment prior to or during repair, the sanitary integrity of the pipe is compromised and it is critical to follow sanitary procedures throughout the repair—not just as it is being returned to service.
Crews responsible for the repair of mains should be aware of the potential health hazards and be trained to carefully observe prescribed construction practices and disinfection procedures. Because of the differences between initial installation and repair, the disinfec- tion requirements for each situation are also different.
The installation of new mains requires that two sets of samples for coliform analysis are collected at least 16 hr apart, or two sets collected 15 min apart after at least a hr rest period. For repaired mains that are main- tained under pressurized conditions at all times, bacteriological testing is not required When required, samples are now specified to be collected at least 16 hr apart, or 15 min apart after a hr rest period.
The purpose of this change is to consider the balance between public health, improved test methods, and timely work completion.
This timing is sufficient to allow bacterial regrowth within the line if there was a con- tamination problem and provides more flexibility in the scheduling of various work activities. Bacteriological testing in accordance with Sec. Failure to pass the bacteriological test requires that the flushing or disinfection process be repeated. It must be remembered that the final water quality test is not the primary means for certifying the sanitary condition of a main.
Four methods of disinfecting newly constructed water mains are described in this standard: the tablet method, the continuous-feed method, the slug method, and the spray method. The utility should decide which of these methods is most suitable for a given situation. Factors to consider when choosing a method should include the length and diameter of the main, type of joints present, availability of materials, equipment required for disinfection, training of the personnel who will perform the disinfection, and safety concerns.
For example, if gas chlorination is the chosen chemical when either continuous-feed or slug methods are being used, use only properly designed and constructed equipment; makeshift equipment is not acceptable when liquid chlorine gas cylinders are used. Thorough consideration should be given to the impact of highly chlorinated water flushed into the environment.
If there is any question that damage may be caused by chlorinated-waste discharge to fish life, plant life, physical installations, or other downstream water uses of any type , then an adequate amount of reducing agent should be applied to water being disposed of in order to thoroughly neutralize the chlorine residual remaining in the water. The tablet method cannot be used unless the main can be kept clean and dry. It cannot be used in large-diameter mains if it is necessary for a worker to enter the main to grout joints or perform inspection because the tablets may release toxic fumes after exposure to moist air.
When using the tablet method, the chlorine concentration is not uniform throughout the main because the hypochlorite solution is dense and tends to concentrate at the bottom of the pipe. The use of the tablet method precludes prelimi- nary flushing.
The tablet method is convenient to use in mains having diameters up to 24 in. The continuous-feed method is suitable for general application. Preliminary flush- ing removes light particulates from the main but not from the pipe-joint spaces.
The chlorine concentration is uniform throughout the main. The slug method is suitable for use in large-diameter mains where the volume of water makes the continuous-feed method impractical and difficult to achieve for short attachments.
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