This document is an American Water Works Association (AWWA) standard. It is not a .. This foreword is for information only and is not a part of AWWA C AWWA C Disinfecting Water Mains. Current; Document Language: English; Published By: American Water Works Association (AWWA). AWWA C and these specifications. Disinfection requirements shall include preventive and corrective measures during construction, forms of chlorine and.
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All samples shall be considered distribution samples, taken and tested in accordance with O. When using the slug method of chlorination, with a minimum contact time of 3 hours, the chlorine concentration shall be measured in the slug at the beginning of the disinfection process, as the slug moves through the watermain, and at the point of discharge. The sampling will typically occur at the point of Flushing, and may take place from sampling ports, hydrants, blow-offs, or premise plumbing.
If, at any time, Contamination is wawa or suspected, the break shall be reclassified as Category 2. If final disinfectant residual is less than 0. If there is evident or suspected chemical Contamination of a watermain, in addition to the procedures in sections 3.
Staged sampling shall be performed as follows: This definition does not include recharging the watermain or a requirement to achieve scouring velocity within the watermain. Skip to main content. For Category 2 — Special Cases, awa site specific plan. After business hours, the operating authority shall send an e-mail to the e-mail address specified by local Ministry office no later than 10 AM the next business day; or in the Special Cases described in sections 3.
The sequence of actions may be varied as appropriate for the specific situation. Example 3 When using the slug method of chlorination, with a minimum contact time of 3 hours, the chlorine concentration shall be measured in the c6511 at the beginning of the disinfection process, as the slug moves through the watermain, and at the point of discharge.
Watermain disinfection procedure |
The procedures are required to be followed in order to satisfy conditions imposed by the Director in a drinking water works permit. Flushing shall continue until the disinfectant concentration at the point of Flushing reaches at least 0. The flow shall be directed to ensure that the sample represents water that has passed through the location of the repair.
The following flowchart is an example of the typical steps required for Category 2 watermain breaks.
Chlorine Concentrations and Contact Times for New Watermains At levels over 10 milligrams per litre, a measurement of total chlorine shall be deemed to be equivalent to a measurement of free chlorine. Watermain repairs involving more than 6 metres of replaced pipe are also classified as Category 2.
If an operating authority believes that contaminated water was directed to users, this will constitute an observation of improper disinfection in accordance with Section of Schedule 16 of O. Flushed water may be discharged from a hydrant, plumbing awwwa Appurtenances. For planned swabbing and hydraulic e. If these disinfectant concentrations cannot c6511 achieved, Flushing shall continue until the disinfectant concentration at the point of Flushing is representative of the system residual in the break area, determined by sampling upstream of the break area and downstream at the Flushing location, or by using documented benchmarks for the area, as long as free chlorine concentrations are at least 0.
Category 1 watermain breaks are not defined as an observation of improper disinfection in accordance with Section of Schedule 16 of O. Examples of typical steps for Category 1, 2 and for special cases are attached as Appendices C, D awwa E respectively.
If Contamination is evident or suspected, the procedures defined under section 3 for Category 2 watermain breaks shall apply. The following flowchart depicts the requirements for special case Contamination sewage or chemical as a result of a watermain break.
Added, modified, replaced, extended; or Taken out of service for inspection, repair or other activities that may lead to Contamination, shall be disinfected before being put into service in accordance with the provisions of the AWWA C — Standard for Disinfecting Water Mains or an equivalent procedure.
Dechlorination of discharged water is required for any water that is directed into surface water or if the discharge into the natural environment causes or is likely to cause an adverse effect, as per Condition 10 awwaa Schedule B of the Municipal Drinking Water Licence.
Operating authorities may awda to provide notification to, or seek advice from, the local Medical Officer of Health at any time.
Discharges of flushed water are also regulated under Condition 4. Contamination is typically not suspected for circumferential breaks or small leaks where flow is maintained from the break until an Air gap is established and where the Air gap is maintained during the repair procedure.
Watermain disinfection procedure
Upon completion of the excavation, the Operator-in-Charge OIC shall conduct a visual inspection to determine the nature of the break. The operating authority will attempt to maintain flow from the break, where possible, until an Air gap is established. Refer to Appendices A and B for a flowchart and pictures to better understand the criteria to determine the categories of watermain breaks.
Due to the chlorine demand exerted by the copper, aqwa minimum chlorine concentration is required following the 24 hour contact time, and the effectiveness of the disinfection process shall be demonstrated by the Microbiological sampling referred to in section 1.
Notification to the local Ministry office is not required for Category 2 watermain breaks unless: The affected watermain s may not be put back in service before the corrective actions and sampling plan are completed unless a Water Advisory is declared. This section does not require that all of the information be recorded on a single form:.
Additional steps shall be undertaken as appropriate to remove Contaminants awaw the watermain, such as:. Disinfectant x651 on final post repair Flushing. Staged sampling shall be performed as follows:. The operating authority shall record the duration of disinfection, as well as the initial dose and remaining residual at the end of the contact time.
v651 The sampling plan shall include as a minimum taking two sets of Microbiological samples at least 24 hours apart. Watermain breaks with evident or suspected Contamination are classified as Category 2. The requirements in this section also apply to temporary watermains. Flow may be discontinued after an Air gap has been created.