What We Do
The Lake Huron and Elgin Area Water Treatment Plants start with untreated lake water and produce safe and pleasant drinking water, also known as potable water. The treated water is free of disease causing organisms, toxic substances, and objectionable tastes and odours.
How it Works
Water Intake
Untreated water flows into the intake crib and through an intake pipe as far as 2 km offshore. The intake cribs are equipped with a chlorine solution, diffused for zebra and quagga mussel control.
Intake Screens
Mechanically cleaned traveling screens remove large objects and debris, such as leaves, sticks, and occasionally fish from the raw water.
Pre-Chlorination
Chlorine is added to the raw water to kill most disease causing micro-organisms and help control taste and odour causing substances.
Flash Mixing
Alum is added to fast-stirring flash mixers which cause very fine particles (such as silt), that would not readily settle out of the water, to clump together into larger particles called floc.
Coagulation-Flocculation
The flocculation basin gently agitates the water to concentrate the suspended solids in an efficient manner. Additional chemicals may be added to the flocculation process either upstream of the flash mixers or as a part of the coagulation-flocculation process, including: powdered activated carbon (for taste and odour control); polymers (as coagulant aids); caustic soda (for pH adjustment); or chlorine (for disinfection).
Sedimentation
In the settling tanks, the speed of the flowing water is slowed down so that the larger suspended particles can settle out by gravity and collect on the tank bottom. The clean water on the surface then spills over the top of the tank, on-route to the filters.
Filtration
Filtration is the final step in removing the particulate matter. Layers of gravel, sand, and anthracite filter out the remaining suspended particles, including fine pieces of floc, algae, silt, and other impurities. When a filter accumulates too many solids it is taken out of service and backwashed.
Post-Chlorination
Chlorine is added to the water to kill any remaining disease causing organisms and to sustain a chlorine residual in the water as it makes its way through the distribution system.
Fluoridation
At the Elgin Area Water Treatment Plant, fluoride is added to the treated drinking water to help prevent cavities. The Lake Huron Water Treatment Plant does not fluoridate.
Clear Well
With the treatment process complete, the purified water collects in a clear well below the filters and is stored before being discharged into the distribution system.
Distribution
High lift pumps distribute the treated water through transmission mains to reservoirs, pumping stations, and consumers. Throughout the system, water is tested regularly to ensure high quality.
