How should a commercial building sand filter system be sized?

The appropriate method for sizing a commercial building sand filter system is to allocate 1 square foot of filter area for each gallon per day (GPD) of wastewater that will be treated. This ratio ensures that the system has sufficient surface area to effectively treat the wastewater generated by the building.

In practice, the GPD measurement represents the anticipated flow of wastewater, which can vary significantly based on the nature of the commercial activities, occupancy levels, and usage patterns. By linking the sand filter size directly to the GPD, the system can achieve optimal performance by providing adequate contact time between the wastewater and the filter media, facilitating efficient filtration and biological treatment.

Sizing based on the number of bedrooms, occupants, or any other less direct measures may not accurately reflect the wastewater generation rates for a commercial setting, leading to inadequate treatment and potential system overload. Therefore, the correct answer reflects established principles in wastewater management that prioritize flow rates for proper system sizing.