Wastewater enters the grit chamber from the collection system, where it is aerated to keep the organic matter in suspension while heavier grit particles like sand and gravel are removed by settling. It is necessary to remove grit because it is abrasive and will rapidly wear out pumps and mechanical equipment. Aerated grit chambers have a detention time of approximately 3-5 minutes at peak flows with a flow velocity of 1ft./sec.
The wastewater then flows through macerators, which shreds larger materials, like pieces of wood and plastics. Macerators shred material so they won’t plug pipes or damage equipment.