There is a finite supply of water on our planet. Treatment of wastewater with a septic system begins with the plumbing in the house. It funnels wastewater to the septic tank. In the tank, solids are separated from the liquids.
Some solids float to the top and others settle to the bottom.
Natural bacteria in wastewater break down the organic solids. Solids not broken down by bacteria are stored in the septic tank until the tank is pumped. They should be pumped out of the tank through the manhole every one to two years. Septic tanks do not destroy disease-causing pathogens. Septic tanks prepare the liquid for final treatment by the soil.