What is the recommended contact time when disinfecting water mains with the chlorine slug method?

The chlorine slug method involves introducing a concentrated dose of chlorine into the water mains to achieve effective disinfection, and the recommended contact time is critical for ensuring that pathogens are adequately inactivated. A contact time of 3 hours allows the chlorine to maintain its potency, ensuring that it effectively disinfects the water system by allowing a sufficient duration for the disinfectant to act on any contaminants present.

During this time, the chlorine must remain in contact with the surfaces of the water mains, as well as with any biofilms or microorganisms that may be present, to minimize the risk of waterborne diseases. Insufficient contact time may lead to inadequate disinfection and could compromise the safety of the water supply, making the 3-hour timeframe a widely accepted standard in the industry. This longer contact time offers a substantial balance between efficiency and effectiveness when managing disinfection processes for water distribution systems.