What is a conventional septic system?
The typical home or commercial building septic system is made up of two primary components: the septic tank and the leach field. Initially, solid and liquid waste leaves a home or commercial building and enters the septic tank.
The purpose of the septic tank is to separate solid waste (sludge), which sinks to the bottom of the tank, from liquids and floatable solids (scum). Intestinal bacteria from human waste assist in breaking down much of the solid waste entering the tank. Over time, the remaining solid waste builds up within the tank and must be pumped and disposed of off site, typically at a municipal wastewater plant.
The remaining liquid waste, along with suspended solids and intestinal bacteria leave the septic tank and flow out and into a leach field for dispersement into the soil. Soils contain natural bacteria that complete the treatment and purification of wastewater before it is recycled into the groundwater.
What causes a conventional (anaerobic, i.e., without oxygen) septic system to fail?
All conventional septic systems have an average life expectancy of between 15 to 20 years, depending on the waste loads entering them. Septic system failure is either mechanical or due to biological clogging. Of the two, 95% of all failures are due to biological clogging.
What is biological clogging (Biomat)?
Septic systems are continuously inoculated with intestinal bacteria when we flush human waste down the toilet. To survive in our intestines, these bacteria protect themselves by secreting a heavy mucous coating. Septic tanks are anaerobic, and because of this the organic load they receive is only partially digested. These organic materials (food for intestinal bacteria) pass out of the tank to the leach field in dissolved forms. The intestinal bacteria carried by the effluent continue to secrete the sticky mucous (polysaccharide slime) and adhere to the soil particle surfaces of the trench and other types of soil-based treatment systems.
Over time, this blocks the soil pore space with slime (commonly referred to as the "Clog Mat" or "Biomat"). As the Biomat builds, the trenches fill with effluent. Eventually effluent from the septic tank cannot pass into the surrounding soil where aerobic bacteria can purify it, and the system fails. Noxious septic waste surfaces over the leach field or backs up into the house leading to septic system failure.
Identifying septic system problems