Septic tanks use a combination of nature and proven technological methods to treat household plumbing wastewater from bathrooms, laundry and kitchen drain. Typically, a septic tank system will consist of a septic tank, a drain field or soil absorption field. The tanks digest organic matter and separate out floatable materials, like oils and grease, from solids in the wastewater. Soil-based systems are used for the discharge of liquid, effluent, which channels clean wastewater from the septic tank into perforated pipes. The pipes are buried in specialised units like leaching chambers that are designed to slowly release the effluent into the surrounding soil or surface water.

There are also alternative systems that utilise pumps or gravity to help the clean wastewater to trickle through less coarse materials like sand, organic matter (peat, sawdust etc.) or constructed wetlands to remove or neutralise pollutants like disease-causing pathogens and minerals like nitrogen or phosphorus that can contaminate the area. These systems can also be used in conjunction with ones that are designed to evaporate wastewater or even disinfect it before it is released into the surrounding soil or surface waters.