1 Intake Crib
Raw water from a surface water lake or reservoir is drawn into the plant through intake structures. Large debris like logs are prevented from entering and zebra mussel control is performed at the intake.
2 & 3 Screens
Smaller debris like fish, vegetation and garbage are removed from the raw water by protective bar and traveling screens before the water enters the low lift pumps.
4 Low Lift Pump Well
These pumps lift the water to flow through the treatment processes by gravity.
5 Pre-oxidation & Primary Disinfection
Disinfectants or other oxidants are added to disinfect or control tastes and odours. The specific processes used are determined by the chemical and biological raw water characteristics.
Coagulants, rapidly add electrochemical charges that attract the small particles in water to clump together as a “floc”. This initial charge neutralization process allows the formed floc to agglomerate but remain suspended.
By slower mixing, turbulence causes the flocculated water to form larger floc particles that become cohesive and increase in mass. This visible floc is kept in suspension until large enough to settle under the influence of gravity.
Flocculated water is applied to large volume tanks where the flow speed slows down and the dense floc settles. Settled floc is removed and treated as a waste product that is discharged to the sewer system.
9 Media Gravity Filtration
Relatively floc free, settled water flows through a media filter by gravity. Filter media are made from layers of anthracite or granular activated carbon and sand. Gravel or synthetic materials support the media. Physical straining removes the remaining floc. Filters are periodically backwashed to clean off accumulated floc and other trapped impurities.
10 Clear Well
Filtered water in the clear well is used to backwash filters and kept in storage to ensure that disinfectants are in contact with the water long enough to inactivate disease causing organisms.
11 Secondary Disinfection
Supplemental chlorine is added to maintain disinfection concentrations while the water is pumped through the distribution system. The purpose is to ensure minimum residual disinfectant levels at the farthest points of the system.