What does primary municipal wastewater treatment primarily remove?

Primary municipal wastewater treatment focuses on the initial phase of wastewater processing, where the main objective is to remove large solids and floatable debris that could interfere with subsequent treatment steps. This process typically involves the use of physical methods such as screening and sedimentation.

During primary treatment, wastewater flows through screens that filter out large floating objects, such as plastics, leaves, and sticks. Following screening, the wastewater enters sedimentation tanks where settleable solids, such as sand, grit, and other particulates, are allowed to sink to the bottom. This removes a significant portion of the solid material from the wastewater, resulting in a clearer effluent that can then move on to secondary treatment processes, which focus on the biological breakdown of organic matter and removal of microorganisms.

While primary treatment does result in some reduction of microorganisms and may lead to a minor decrease in certain chemical contaminants, its primary efficacy lies in the removal of larger solids and debris. This initial treatment is crucial for preventing damage to pumps and other equipment in subsequent treatment processes. Nutrients and salts, on the other hand, are typically addressed in more advanced treatment stages.