All wastewater treatment systems, either municipal or single family onsite wastewater systems include:

• Collection system
• Treatment components
• Dispersion into the environment

In this picture of an example onsite wastewater system:

• #1 is the building sewer or collection system leading to
• #2 the septic tank which is the first step in the treatment system followed by
• #3 and #4 the drainfield where the final treatment and dispersal into the environment happens.

The septic tank holds wastewater long enough for solids to settle to the bottom and fats, oils, and greases will float to the top. This collection system is a key and primary component that needs maintenance. When solids accumulate, they reduce the available clear zone and consequently the residency time for treatment.

Conventional systems, as shown in this picture, is where liquid wastewater from the middle third of the septic tank exits the tank and is spread evenly throughout the drainfield. Once in the drainfield, the wastewater percolates into the soil, which reclaims the water for future reuse by naturally removing harmful bacteria and some nutrients.

A properly sized drainfield is in the upper soil profile which is a friendly environment for the aerobic bacteria that treat our wastewater. Additionally, there is an unsaturated zone of separation from the drainfield to the seasonal high-water table. It has been established that when we percolate wastewater through unsaturated soil, we can discharge the treated wastewater into the groundwater which either recharges our groundwater aquifers or eventually discharges into our streams and lakes after proper treatment.