Fifty years ago there was no great concern about what to do with "waste water" from our homes on septic systems. But times have changed. Now there is a great deal of concern. The Federal EPA and local health departments are now re-defining what the homeowner's responsibilities are regarding waste water discharges when defined as "Onsite Disposal Systems or Septic Systems". This makes it imperative that homeowners with septic systems understand how a conventional septic system works and what causes these septic systems to fail.
The basic functions of the three design components of a septic system, septic tank, disposal field and soil, are described in "What is a Conventional Septic System?" The factors that can contribute to premature failure are described in "Problems / Solutions". The homeowner needs to understand what causes 95% of all septic system failures. The cause is commonly referred to in the onsite or septic industry as Biomat clogging of the soil.
We need to realize that what we do with our human generated waste is not natural. Land mammals don't normally put their wastes in water. Hippos don't use their pools; beavers don't use their ponds; otters don't use their streams. We do this odd thing in nature. We put our wastes in water to use gravity to take them away from us. Now, we are stuck with them. By putting these wastes in water, we have removed them from the environment that contains the organisms capable of digesting, breakdown and recycling the organic compounds and purifying the water. Simply stated, the organisms that degrade and process organic waste are aerobic not aquatic.
We put our wastes in water then send it to a totally unnatural place; a man made, airless, dark, sunless septic tank buried in the ground. In the septic tank, the intestinal bacteria in our feces don't die after leaving our bodies as they would have had we deposited our waste on the surface of the soil or in the leaf litter as our ancestors did. The septic tank is anaerobic (without oxygen), as are our intestines, and there is no exposure to sunlight, again like our intestines. These bacteria prefer the 98.6 degree temperature of our intestines but they manage to survive in the 55 to 60 degrees of the typical septic tank. Within the septic tank these bacteria do perform a very important function. They secrete enzymes and proteins that allow separation of the organic solids into settled "sludge" and floating "scum". This process of separation and settling removes the majority of the solid organic waste from the water we used to transport it away from us and into the septic tank. Now the clarified, liquid effluent can be disposed of.
The clarified effluent flows out of the septic tank through piping to the same place, day after day for decades. This place we send it is an unnatural man made void in the soil called a disposal field. The disposal field is where the liquid effluent will be treated and recycled back into the environment. In every cup of liquid effluent are countless numbers of intestinal bacteria. Like the septic tank, the intestinal bacteria manage to survive within the disposal field which, again, is basically anaerobic, dark and without sunlight. They "set up house keeping" and form a colony on the various surfaces within the disposal field.
The intestinal bacteria eventually form a continuous colony covering all of the infiltrative surfaces of the soil in the disposal field. Within this continuous colony, the intestinal bacteria secrete or produce a viscous mucoid slime. This mucoid slime is the matrix in which the intestinal bacteria live. This slime is called Biomat by the septic or onsite industry. Over time, the intestinal bacteria colonize all the contiguous soil pore spaces and clog them with Biomat slime. As the depth of the Biomat within the soil pores thickens, the free passage of liquid through the Biomat is inhibited.
At or near twenty years of Biomat clogging of the disposal field soils, the amount of liquid put into the septic system each day slowly becomes greater than the amount of liquid that can pass through the Biomat and be absorbed into the soil. The amount of liquid that doesn't get absorbed or can't pass out of the disposal field is now "excess" liquid. It has to go somewhere and it does. The liquid rises within the septic system and either finds a way to the surface of the soil over the disposal field or septic tank, or it backs up into the house. This is defined as failure. This increase in depth penetration into the soil pores by intestinal bacteria, and the clogging of the pore spaces with Biomat slime, is the cause of 95% + of all septic system failures.
Before the Pirana System, replacing the disposal field or engineering a complicated treatment system were the only viable solutions.