What is the average percentage of solids found in primary sludge?

The average percentage of solids found in primary sludge is typically in the range of 8-12%. Primary sludge, which is generated during the primary treatment phase of wastewater treatment, consists mainly of organic matter that has settled out from the wastewater.

This percentage indicates that primary sludge contains a significant amount of solids, reflecting the removal of heavier, settleable materials found in influent wastewater after initial screening and sedimentation processes. The solids in primary sludge are largely composed of debris and organic material from the wastewater, leading to the higher concentration compared to other stages of treatment sludge.

The other ranges mentioned do not accurately represent the common concentrations of solids found in primary sludge. Options representing lower or higher solid percentages do not align with typical operational data and the characteristics observed during primary treatment processes.