Municipal WW sludges must have what minimum percent solids to be accepted for landfill disposal?

• A. 5%
• B. 10%
• C. 20%
• D. 50%

Answer: (C)

This item tests the dewatered solids level required for sludge to be accepted at a landfill. Sludge that has enough solids is far easier to handle, transport, and place in a landfill because it generates much less leachate and odors and is more stable in the waste mass. About 20% solids is the threshold commonly used because it strikes a practical balance: it significantly reduces moisture content without requiring excessive processing. If sludge has only 5% or 10% solids, it’s too wet, creating handling difficulties and high leachate production, which landfills typically won’t accept. A figure like 50% solids would be unnecessarily high and costly for typical municipal wastewater sludges.