The comminuter is essentially a large grinder which reduces solid objects in the inflow to smaller pieces. This reduces wear on equipment in the plant and lowers the risk of jamming. The water then enters the grit chamber, where small stones and sand settle out. Removing sand and larger solid objects helps extend the life of equipment. The grit and screenings are trucked to landfills.
Air is mixed with the wastewater in the grit chamber.
One noticeable difference between the treatment process at Winslow and at Delaware No. 1 is that air is repeatedly mixed into the wastewater at Winslow. At Delaware No. 1, pure oxygen is mixed with the wastewater in the aeration tanks. Activated sludge from the leveling ponds is mixed with the wastewater in the equalization tanks to begin biological digestion of organic contaminants. In the oxidation tanks, primary sludge settles to the bottom and can be removed. The wastewater is able to mix with air at this point.