Which of the following is required to determine the size of spray area for an OSSF spray irrigation system?

Determining the size of the spray area for an On-Site Sewage Facility (OSSF) spray irrigation system relies heavily on understanding both the rate of irrigation permitted in the specific area and the flow rate of wastewater. The correct choice integrates these critical aspects.

The rate of irrigation (R) is essential because it indicates the maximum amount of water that can be applied to the soil without causing surface runoff or subsurface drainage. This is crucial for ensuring that the system efficiently reuses treated wastewater while not overwhelming the local soil capacity.

The flow rate (Q), measured in gallons per day, provides the volume of wastewater that needs to be managed by the spray irrigation system. Together, R and Q help to establish how large the spray area must be to effectively distribute the wastewater over a sufficient area to prevent saturation and promote proper absorption.

In this context, while other factors like the aerobic plant capacity and soil acceptance rate are important for the overall design and function of an OSSF, they do not directly contribute to calculating the necessary spray area size in the same way that the rate of irrigation and flow rate do. Therefore, focusing on the rate of irrigation along with the daily flow rate gives a clearer picture of the required spray area size to ensure efficiency and compliance