Definitions for "Biomat"
Biomat is a biological growth that over time prevents wastewater from absorbing past the walls of the drainfield. For more information, refer to the biomat section on the Failed Septic System? page
Layer of organic material that forms below the gravel layer in a leaching bed. If it becomes too deep, it can prevent proper drainage.
The biological mat (biomat) is a black, jelly-like mat about one to two inches thick, that forms at the gravel-soil interface at the bottom and sidewalls of the drainfield trench. The biomat is composed of microorganisms (and their byproducts) that anchor themselves to soil and rock particles, and whose food is the organic matter in the septic tank effluent. Since the biomat has a low permeability, it serves as a valve to slow down and control the rate of flow out of the trench into the drainfield soil, and also serves as a filter to provide effluent treatment. Also known as a clogging mat.