Which term refers to the solids separated during municipal wastewater treatment?

• A. Sludge cake
• B. Effluent
• C. Sewage sludge
• D. Biosolids

Answer: (C)

Wastewater treatment splits the incoming water into two main streams: the clarified liquid that becomes effluent and the solids that settle out, which are called sewage sludge. This term specifically targets the solids removed during the treatment process before any stabilization or further processing. After stabilization (digestion, drying, etc.), that material may be referred to as biosolids if it meets regulatory requirements for safe handling or land application. Sludge cake isn’t a standard term for the general solids produced, and effluent refers to the liquid portion leaving the plant.