How do grit chambers remove sand, coffee grounds, and eggshells from sewage?

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Aerial view of wastewater treatment basins with circular clarifiers; overlaid toilet graphic and arrow with text reading: “Where does it go?” — wastewater treatment All the sewers in your neighborhood end up here.

Grit chambers remove heavy inorganic solids like sand, coffee grounds, and eggshells by utilizing the physical principle of gravity.1

These chambers are designed as long, narrow tanks that reduce the velocity of the incoming sewage flow. By slowing the water down, the heavier particles lose their suspension and settle to the bottom of the tank, while lighter organic matter remains in the flow to be treated in subsequent stages.1

This process is essential in wastewater treatment because these abrasive materials can cause significant wear and tear on pumps and other mechanical equipment within the plant. Removing grit is especially critical in areas with combined sewer systems, where storm runoff frequently introduces high volumes of silt, sand, and gravel into the system.1