The sludge from a primary clarifier typically contains what percentage of solids?

The sludge from a primary clarifier typically contains about 4% to 6% solids. This is significant in wastewater treatment because primary clarifiers play a crucial role in the removal of suspended solids and organic matter from wastewater. The primary treatment process allows for the settling of heavier solids, which then form sludge at the bottom of the clarifier.

Understanding the solid content in the sludge is important for subsequent treatment processes, such as thickening and digestion, which are affected by the concentration of solids. A concentration of 4% to 6% indicates that the sludge is in a manageable range for downstream processing and helps in optimizing resources, such as energy and chemical use, during treatment.

In contrast, the other options suggest solid concentrations that are either too low or too high for what is typically observed in primary clarifier sludge. Lower concentrations would not adequately represent the sludge produced during primary treatment, while higher concentrations could lead to operational challenges in handling and processing the sludge effectively.