What does a septic system not include?

A septic system typically consists of a septic tank and a leach field, which are essential components for treating and disposing of wastewater from a household. The septic tank is designed to separate solids from liquids and facilitate the anaerobic digestion of the organic material present in wastewater. Once this process occurs, the liquid effluent is then directed to the leach field, where it percolates through the soil for further treatment and final disposal.

Filtration, while important in other systems, is not inherently a part of a conventional septic system. In standard septic setups, the primary functions of solid separation and biological treatment occur within the tank, and the leach field serves more as a means of distributing the already treated effluent into the soil rather than employing a filtration process.

A pumping station, while useful in managing wastewater in certain larger or more complex systems, is not typically a component of a traditional septic system. Such stations are generally used to move wastewater over long distances or to higher elevations where gravity alone would not suffice. In standard residential septic systems, gravity often plays the key role, reducing the necessity for a pumping station.

Thus, filtration distinguishes itself as the component not commonly included in a standard septic system, making it the correct answer to the question.