What is the proper detention time for disinfecting a water storage tank that reaches a free chlorine residual of 10 mg/L?

The proper detention time for disinfecting a water storage tank is crucial to ensure that the water is adequately treated and safe for consumption. When a free chlorine residual of 10 mg/L is achieved, a detention time of 6 hours is typically recommended. This duration allows sufficient contact time for the chlorine to effectively eliminate pathogens and microorganisms present in the water.

The guideline is based on the understanding that the longer the contact time with chlorine, the more effective the disinfection process will be. Six hours at this concentration provides a good balance between operational efficiency and public health safety, allowing the disinfectant to work thoroughly without unduly prolonging the process.

Shorter detention times may not allow enough time for effective disinfection, which could lead to insufficient treatment of the water. Conversely, excessively long detention times may not yield significant additional benefits and could be inefficient or impractical for water management systems. Therefore, selecting a 6-hour period aligns with standard industry practices for ensuring that water stored in tanks meets health and safety standards.