What is the required chlorine concentration for chlorination after 30 minutes of contact time?

The required chlorine concentration for effective disinfection after a 30-minute contact time is typically established to ensure that pathogens are adequately neutralized in the water. A concentration of 2 PPM (parts per million) is recognized as sufficient for achieving this goal while balancing safety and efficacy.

In chlorination, maintaining an appropriate level of chlorine is essential for killing bacteria, viruses, and other microorganisms present in source water. The 2 PPM concentration allows for sufficient residual chlorine that can effectively reduce microbial load while considering the likelihood of contaminants that may be present in typical water sources.

In contrast, higher concentrations such as 5 PPM or 10 PPM may pose health risks and result in too much chlorine residual, which can create unpleasant tastes and odors in drinking water, complicating water treatment processes. Thus, 2 PPM is seen as the standard for effective disinfection over a 30-minute contact period, making it the correct choice.