How Does the Biomat Form?
As the effluent is discharged into the SAS, bacterial growth develops beneath the distribution lines where they meet the gravel or soil. This layer is known as the clogging mat, clogging zone, biocrust, and bioformat. It’s also referred to by some as the “slime layer” and it’s easily visible as a usually-gray slimy layer in the soil displayed if one excavates a cross-section of an absorption system trench. This biomat (biological mat) is a black, jelly-like layer that forms along the bottom and sidewalls of the drainfield trench. This clogging zone [eventually] reduces infiltration of wastewater into the [surrounding] soils.
