Wastewater from washing out garbage bins should pass through what before entering sewer system?

• A. A sand filter
• B. A carbon bed
• C. A chlorine bath
• D. A grease trap

Answer: (D)

Wastewater from washing garbage bins often carries fats, oils, and grease. To prevent sewer blockages and odors, this wastewater should first pass through a grease trap before entering the sewer system. A grease trap slows the flow and separates fats and oils (which float) from the water, while solids settle out. The captured grease and solids are removed later, keeping the sewer lines clear. The other options don’t specifically target grease: a sand filter mainly removes solids, a carbon bed targets odors and some chemicals, and a chlorine bath disinfects but doesn’t prevent grease blockages. So a grease trap is the appropriate pre-sewer treatment.