How many times should dosing occur in a 24-hour period for intermittent sand filters?

Intermittent sand filters require a specific dosing frequency to ensure proper treatment of effluent and to maintain the filter's effectiveness. The correct answer indicates that dosing should occur between four to eighteen times within a 24-hour period. This dosing frequency allows for adequate aeration, maximizing the biological activity necessary for breaking down organic matter and promoting the overall purification process.

Frequent dosing helps prevent saturation of the filter medium, ensures efficient water distribution, and allows for optimal contact between the effluent and the sand particles, which is crucial for the filtration process. By distributing the effluent over multiple smaller doses instead of one large dose, this approach enhances the ability of the filter to treat the wastewater thoroughly.

Less frequent dosing, such as once a day or even a limited number of doses, would not provide the same level of treatment and could lead to filter overload, reduced treatment efficiency, or even system failure. Therefore, maintaining the dosing within the range mentioned ensures that the system operates effectively, providing high-quality effluent while protecting the environment.