According to normal conditions, what are the proper ppm and hours needed for chlorine to disinfect the BEAR water distribution system?

In the context of disinfecting the BEAR water distribution system, the correct parameters involve using a concentration of 10 parts per million (ppm) of chlorine and allowing it to sit for a duration of 24 hours. This disinfection method is essential for ensuring that any harmful pathogens present in the water system are effectively neutralized.

The reason for the specific combination of 10 ppm and 24 hours lies in the effectiveness of chlorine as a disinfectant. At this concentration, chlorine is able to penetrate microbial cells and effectively kill off bacteria and viruses over an extended exposure time. The 24-hour duration provides sufficient time for the chlorine to interact with and eliminate a wide range of microorganisms, thereby ensuring a higher level of safety and compliance with health standards.

When lower concentrations or shorter contact times are utilized, such as 20 ppm for 12 hours or even 10 ppm for 12 hours, the disinfection efficacy may not be adequate to eliminate all pathogens. Thus, adhering to the guideline of 10 ppm over a full 24 hours maximizes the disinfection capacity of the chlorine, making it the best practice for maintaining water quality in the distribution system.