What is the recommended chlorine dosage when disinfecting a water main using the slug method?

The recommended chlorine dosage for disinfecting a water main using the slug method is 300 mg/L. This method involves introducing a concentrated dose of chlorine into the water system to effectively disinfect the main and eliminate any pathogens or harmful microorganisms present.

Using a dosage of 300 mg/L is considered optimal because it strikes a balance between being sufficient to achieve effective disinfection while avoiding excessive chlorine levels that could cause unpleasant tastes, odors, or potential negative effects on water quality. The slug method typically involves brief contact times, and a higher concentration helps ensure that the chlorine reaches all areas of the system, especially where there may be dead ends or low flow.

This dosage is also in line with industry standards and guidelines provided by agencies responsible for water quality and public health, ensuring safe and effective treatment of drinking water.