Secondary clarification tanks at Michelson Water Reclamation Plant, Irvine Ranch Water District, Irvine, California, USA. After being treated in aeration tanks, water flows to secondary clarifications tanks where it stays for about two hours to allow the solids settle out. Upon leaving the clarifiers, water (secondary effluent) has about 90% of all the contaminants removed. A small amount of coagulant (aluminum sulfate or alum) is added at this point to remove remaining particles in the next step. The Michelson Water Reclamation Plant in Irvine treats up to 18 million gallons of wastewater (sewage) per day. The recycled water can be used for any purpose except drinking, like landscape irrigation in parks, golf courses, school grounds, city street medians, other public areas. The recycled water is piped through a completely separate recycled pipeline system.