To effectively disinfect water wells, how long should free chlorine be applied at a concentration of 50 mg/L?

When disinfecting water wells using free chlorine at a concentration of 50 mg/L, it is crucial to allow sufficient contact time for the disinfectant to effectively kill pathogenic microorganisms present in the water. The recommended contact time for chlorine applications typically falls within a range of 12 to 24 hours. This duration ensures that the chlorine can penetrate and act upon various contaminants, including bacteria and viruses, which are common concerns in water quality.

While shorter exposure times may suffice in certain circumstances, especially at higher concentrations, a 12 to 24-hour duration is generally accepted for maintaining effective disinfection without risking the survival of resistant organisms. The longer contact period also helps in ensuring that any biofilm or sediment present in the well is adequately treated.

Using this guideline not only adheres to best practices in water treatment but also contributes to safe drinking water initiatives, ensuring that the final water product meets health standards. On the other hand, options suggesting durations outside this established range may not provide the necessary effectiveness and thus would be less suitable for achieving thorough disinfection.