What does a septic tank do?
A septic tank is a chamber of concrete or other material that has one or more chambers that receives wastewater. Grease, oils, fats, and wood fiber (from paper products) float forming a scum layer. The scum layer slowly liquefies by microbial action. Grit, diamond rings, and heavier solids sink to the bottom, as do larger organics. The settled solids also slowly liquefy due to anaerobic bacterial activity. (Oxygen is required to break down plant and animal materials contained in wastewater.) So very little actual treatment occurs as the only oxygen present is that which is dissolved in the influent, the oxygen demand is about 20-30 times as much. So a septic tank allows fats to float, and settles solids, slowly liquefying a portion passing it out into the leach field. Virtually all that passes into a septic tank either stays or passes into the leach field.
