What process is primarily used in primary wastewater treatment?

Primary wastewater treatment primarily involves the removal of suspended solids and organic matter through settling or sedimentation. This process is designed to reduce the solids in the wastewater before it undergoes secondary treatment.

During primary treatment, wastewater is typically held in large settling tanks, where heavier solids settle to the bottom, forming sludge. Meanwhile, lighter materials such as oils and grease rise to the surface and can be skimmed off. This step is crucial for reducing the organic load entering subsequent treatment stages, as it helps to minimize the amount of material that must be further treated biologically.

The other processes listed play roles in different stages of wastewater treatment. While filtration involves physical removal of contaminants, it is not the primary focus of the initial treatment. Biological treatment is associated with secondary treatment processes that rely on microorganisms to further break down organic material. Chemical precipitation targets inorganic nutrients, generally used later in the treatment process to remove substances like phosphorus and nitrogen. Thus, the process of removal of suspended solids and organic matter by settling is the hallmark of primary treatment.