Biomat

Also referred to as clogging mat. A black, jelly-like layer of organic material which forms at the bottom and sides of the infiltrative surface of a drainfield. The biomat aids in wastewater treatment by removing pathogens and by ensuring that wastewater moves through soil at a slow, steady rate (especially important for medium and coarse soils). If improperly treated wastewater is regularly discharged into the drainfield, the biomat can become too thick and clog the system, preventing wastewater dispersal. <