For how long should a 200 ppm chlorine solution be applied for disinfection of potable water?

A 200 ppm chlorine solution is commonly used in the disinfection of potable water, and the duration for which it should be applied plays a critical role in ensuring effective pathogen inactivation. The standard practice for chlorination of drinking water often suggests that a contact time of about 30 minutes to 1 hour can be adequate for proper disinfection when chlorine concentrations are at 200 ppm.

However, aiming for the higher end of the recommended contact time, applying the solution for 3 hours can provide an additional layer of safety and assurance in the disinfection process. This extended duration allows for any variations in water temperature, organic content, and pH levels that could affect chlorine's effectiveness, maximizing the potential of chlorine to eliminate pathogens and ensuring the water is safe for consumption.

This emphasis on contact time aligns with guidelines set by health organizations, which often recommend conservative practices in water treatment to ensure safety standards are met. Therefore, while a shorter time might technically suffice under ideal circumstances, the practice of using a 3-hour application period accounts for real-world variability and strengthens the disinfection process.