What is the minimum required chlorine residual for free chlorine in water treatment?

The minimum required chlorine residual for free chlorine in water treatment is typically 0.2 mg/l. This level ensures that there is sufficient chlorine present to effectively disinfect water, providing a residual that helps maintain microbial control throughout the distribution system.

Chlorine is added to water to eliminate pathogens, and maintaining a residual level is crucial for ensuring ongoing protection as the water travels through the distribution system. A level below 0.2 mg/l may not provide adequate disinfection, while levels above would generally be more than necessary for maintaining safety without causing taste or odor issues.

This threshold is recognized in various guidelines and regulations, reflecting best practices in water treatment to safeguard public health.