How does it work? A septic tank creates a large quiet compartment to allow solid material to settle out the waste water and collect in the tank. Once the solid materials settle out then the discharge either goes into the soil where microorganisms remove the pollutants before the waste water enters the ground or the discharge goes into an aeration treatment compartment where again micro organisms break down and remove the pollutants. Why do you need a septic? Over years of operation, accumulated solids begin taking up too much room in the tank reducing the volume available for settling. When ...