Question 86

The solution must remain in the system for a minimum of 3 hours.

For effective disinfection of a potable water system using a solution at 200 ppm, it is necessary for the solution to remain in the system for a minimum of 3 hours to ensure adequate microbial kill and system sanitation.

A) 1

Option A is incorrect because a duration of only 1 hour is insufficient for the disinfectant to effectively eliminate pathogens in the system. Research indicates that shorter exposure times may not achieve the necessary disinfection levels for potable water systems.

B) 2

Option B is also incorrect as 2 hours does not meet the minimum requirement for effective disinfection. While this duration is better than 1 hour, studies have shown that a longer contact time is essential to ensure the efficacy of the disinfectant at 200 ppm.

C) 3

Option C is correct because a minimum contact time of 3 hours allows the disinfectant to effectively act on any potential pathogens within the potable water system. This duration is consistent with guidelines for adequate disinfection practices.

D) 6

Option D is incorrect as it exceeds the required minimum duration. While longer contact times can enhance disinfection, the stipulated minimum for a 200 ppm solution is 3 hours, making 6 hours unnecessarily lengthy for this specific requirement.

Conclusion

The minimum required contact time of 3 hours for the disinfectant solution at 200 ppm is essential for ensuring the safety and cleanliness of the potable water system. Options A and B do not provide sufficient time for effective disinfection, while option D, although safe, is beyond the required minimum. Thus, option C is the only correct choice that aligns with established disinfection standards.