Primary Treatment
			Primary treatment is provided in order to remove 85% of organic and inorganic solids from raw wastewater. The process is a simple one: screened wastewater is detained undisturbed for one to two hours in primary sedimentation tanks, as solids (primary sludge) settle to the bottom of the tanks, or float to the surface. Chemicals are added to improve the efficiency of the settling process. Sludge is collected in sumps where it is pumped to anaerobic digesters for further processing. All incoming wastewater receives advanced (chemically assisted) primary treatment. As of 1998, all primary effluent receives secondary treatment.