What is the formula for water disinfection effectiveness involving chlorine?

The formula for water disinfection effectiveness involving chlorine is based on the principle that the effectiveness of chlorine as a disinfectant is determined by both its concentration and the amount of time it is in contact with the water. The correct formulation is a multiplication of chlorine concentration and contact time.

When chlorine is introduced into water, its disinfecting power does not merely depend on how concentrated the chlorine is or how long it is present independently; rather, these two factors work together synergistically to achieve effective disinfection. Higher concentrations of chlorine will generally lead to a faster reaction rate, but without sufficient contact time, the disinfection may not be complete. Conversely, lower concentrations may require extended contact times to achieve the same level of disinfection.

Therefore, multiplying chlorine concentration by contact time allows for a more comprehensive understanding of how these variables interact and ensures that the water disinfection process is effective. This formula helps water treatment professionals calculate the necessary conditions for adequate disinfection, leading to safe drinking water.