One purpose of preliminary treatment is to remove materials that are not

• A. Readily Biodegradable
• B. Non-biodegradable
• C. Hazardous
• D. Thickening

Answer: (A)

Preliminary treatment aims to protect downstream processes by removing solids that will not break down quickly. By screening out items like grit, plastics, and other non-biodegradable materials, the system avoids clogging, equipment damage, and excessive buildup that could disrupt pumps and later treatment steps. The goal is to reduce the load of materials that resist degradation, so the biological and physical treatments that follow can operate more smoothly and efficiently. Readily biodegradable substances, on the other hand, would be handled by the biological treatment later, so they aren’t the primary targets of preliminary treatment. Hazardous materials require special handling beyond basic preliminary steps, and thickening is a sludge processing step not specifically the purpose of preliminary treatment.