What occurs during the Primary Treatment of wastewater?

During the Primary Treatment of wastewater, the primary focus is on the physical processes involved in the separation of solids from liquids. This treatment stage typically involves the use of sedimentation tanks or clarifiers, where the heavier solids settle at the bottom, forming a sludge, while the lighter materials, such as fats and oils, may float to the surface as scum. This step effectively removes a significant portion of the total suspended solids and organic matter present in the wastewater.

Additionally, while the primary treatment does lead to some degree of organic matter digestion, the main purpose is the physical separation. As a result, this stage prepares the wastewater for further treatment processes, such as secondary treatment, where biological processes would further reduce organic material.

The other options presented relate to processes that occur either later in the wastewater treatment cycle or in different contexts altogether. Disinfecting water for drinking is part of the advanced treatment or tertiary stage, seeding beneficial bacteria is typically associated with the secondary treatment, and filtering water through sand is a common practice in later stages of water treatment processes.