How is wastewater from a private sewage system typically treated?

Wastewater from a private sewage system is primarily treated through biological and physical processes. In this context, biological processes involve the use of microorganisms to decompose organic matter found in wastewater. These microorganisms, such as bacteria, break down the waste, leading to a reduction in harmful pathogens and pollutants. This biological treatment is essential for making wastewater safe to return to the environment.

Physical processes may include sedimentation, where solid particles settle out from the liquid, and filtration, which removes remaining impurities. These combined biological and physical treatments help in effectively purifying wastewater before it can be released into the environment or reused.

In contrast, the other methods listed are either ineffective for treating sewage or not used in traditional systems. Evaporation is not a practical method for treating large volumes of wastewater; it is limited, depends on environmental conditions, and does not remove contaminants. Chemical filtration is a part of some treatment processes but is not the sole method used in private sewage systems, as biological treatment is more prevalent and effective. Pumping wastewater directly into a stream is not an accepted method of treatment and can lead to severe environmental pollution, as untreated sewage can harm aquatic ecosystems and public health.