What filter loading rate should be used for sizing raised filter beds for residences with up to 1500 gpd?

The correct filter loading rate for sizing raised filter beds for residences with a wastewater flow of up to 1500 gallons per day typically falls at 4 gallons per square foot per day. This rate is based on established engineering standards and practices for septic systems. It reflects a balance between efficient waste treatment and maintaining the capacity of the filter bed to accommodate the effluent without causing undue stress or operational failure.

Using this loading rate ensures adequate distribution of effluent across the filter bed, allowing for proper filtration and aerobic treatment of wastewater. It helps to prevent clogging and promotes effective microbial activity, which is essential for breaking down organic matter in the wastewater. This loading rate also considers the soil's absorption capacity and the specific design needs for residential installations, ensuring that the system remains functional and compliant with local health and safety regulations.

The other loading rates would not align with the standards for typical residential systems designed for up to 1500 gpd, as they may either underload or overload the system, potentially leading to insufficient treatment or premature failure of the filter bed.