Wastewater treatment. Solids removal area of a wastewater treatment plant. The first stage of wastewater treatment is the removal of large solids such as wood, dead animals and sanitary towels. The water then moves to this area where sand and grit are removed. It is important to remove sand and grit at an early stage as they can damage pumps and pipes. All solids removed are sent to landfill. Photographed at the Jones Island wastewater treatment plant, Milwaukee, USA.