Water Treatment Description


This award winning water treatment facility provides drinking water for the nearly 105,000 residents of Wilmette, Village of Glenview, Village of Golf, Village of Kenilworth, and portions of Prospect Heights.

Treatment Description

Raw water enters the plant through intake lines out in Lake Michigan. During the summertime, a small dose of chlorine is fed into the intake pipes to help control the growth of zebra mussels. After traveling under the lake bed to the low lift pumping station, the raw water receives a second (pre) chlorine dose in the low lift pump suction well for disinfection. Next, the water is lifted about 15 feet by low lift pumps and delivered to the water plant.

Treatment chemicals – including coagulant (for the removal of turbidity, or “cloudiness” in the water), fluoride (for prevention of dental cavities) and powdered activated carbon (for taste and odor removal) – are fed at the water plant’s in-line water mixers. This is the chemical pretreatment step, before distribution to the mixing-settling basins. Typically, no more than a teaspoonful of chemicals is added to every 100 gallons of water treated.

Following this, the pretreated water enters one of six slow mix basins for the flocculation step. In this step, “floc” particles are formed when alum reacts with the raw water, forming a sticky, gelatinous precipitate. Gentle mixing is applied in each basin causing the floc particles to collide with and entrain natural turbidity particles in the raw water. In the sedimentation step that follows mixing, 90% of these floc particles settle out.

After sedimentation, the treated water is delivered to the dual media filters for the final polishing step, filtration. The filtered water receives a second (post) dose of chlorine to maintain a residual in the distribution system and a dose of ortho-polyphosphate (for corrosion inhibition in the water mains) before entering the water plant’s underground clearwell/reservoirs.



847-853-7535 (24 hours)
200 Lake Avenue
Wilmette, IL 60091