If you’re a resident or not it is likely that you live in a city that has a public sewer system. The septic tank is needed in those that don’t have access to these facilities. They can then remove harmful bacteria before sending it to the ground for the toilet tank.
It’s designed to remove solid waste from wastewater. It then settles into sludge that is deposited on the floor in the tank. A layer of scum debris of oil and grease floats above.
It is possible to understand the fundamental functions of a septic system by thinking about how it separates solid waste from wastewater. The solid waste then settles on the bottom as an sludge. Light grease- and oil-based waste sits on top.
The middle water contains nitrogen and phosphorus that can be utilized to fertilize.
This informational video from The Desert Echo explains how employees at contractors for working on septic pumps.