What is one requirement for alternative media in a buried sand filter?

The primary requirement for alternative media in a buried sand filter is that it must have the same hardness or greater than what is required for standard sand filters. This ensures that the media can adequately support the mechanical and physical filtration processes that are essential for effective septic system performance. Hardness in this context refers to the ability of the media to withstand compaction and maintain structural integrity under various conditions, including saturation and potential pressures from the surrounding soil.

Alternative media such as gravel, crushed stone, or specially engineered materials must meet or exceed these hardness standards to ensure that they can effectively filter effluent and allow for proper drainage without collapsing or becoming compacted over time. This contributes to the longevity and effectiveness of the filter system, ensuring that effluent is treated properly before entering the surrounding environment.

The other choices reflect characteristics that may not align with the primary physical requirements for alternative media selection in filtration systems. For example, biological activity and chemical reactivity are important for certain aspects of treatment but are not core requirements for the structural characteristics needed in a buried sand filter context.