In a shallow buried trench system, can the piping be less than in a conventional leaching bed?

• A. Yes, because the effluent is highly treated and there is no biomat formed; therefore, the soil can accept more effluent compared to septic tank effluent.
• B. No, it must be the same size.
• C. Yes, regardless of treatment level.
• D. No, it must be larger due to biomat formation.

Answer: (A)

In a shallow buried trench system, how much soil can accept and treat the effluent depends on the quality of the effluent and whether a biomat forms at the infiltration surface. When the effluent is highly treated, it carries far fewer solids and less organic matter, so the tendency for a biomat to form is reduced or eliminated. That keeps the soil’s infiltration rate higher, meaning the same amount of effluent can be spread using smaller distribution piping than in a conventional leaching bed that receives less-treated septic tank effluent. In other words, better-treated effluent can be distributed through a smaller pipe network because the soil isn’t blocked by clogging layers and can accept water more readily. If the effluent were not as well treated and biomat formation occurred, infiltration would slow, and you’d typically need more or larger piping to prevent overload.