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Need for Public Water Supply
Why Treat Water?
• Society realized long ago that human health and
the welfare of the general population are
improved if public water supplies are treated
prior to use.
• Nearly all structures require a water supply.
• Appropriate flow rate, pressure, and water quality
are necessary for effective use.
Uses of Water
• Food preparation
• Fire protection
• Industrial purposes
• Drinking water = Potable water
Water Supply System
II. Water Sources and Treatment
• Water Cycle
• Surface water
• How do these vary in
Sources of Water
• Primary source of drinking water
• Porous consolidated rock or
• Groundwater fills spaces
• Wells and pumps used to remove
Courtesy USGS at http://pubs.usgs.gov/circ/circ1139/htdocs/boxa.htm
This image was reproduced from groundwater.org with the permission of The
Groundwater Foundation. © 2010 The Groundwater Foundation. All Rights
Sources of Water
• Lakes, reservoirs, rivers
• Rivers dammed to create reservoirs
• Reservoirs store water during heavy
Lake Tuscaloosa Dam
Origins of “Contamination”
• Contaminant: Any physical,
chemical, biological, or
radiological substance or
matter that has an adverse
effect on air, water, or soil.
• Naturally occurring
• Point-source (end-of-pipe)
• Non-point source
(agricultural, land use)
Major Water Quality Indicators
• Microorganisms, Disinfectants & Disinfection
Byproducts, Inorganic Chemicals, Organic
Chemicals, & Radionuclides
• Amount of treatment
depends on quality of the
• Ground water requires less
treatment than surface
Courtesty USGS http://pubs.usgs.gov/fs/2004/3069/
The city of Salem water treatment
facility withdraws water from the
North Santiam River.
Water Treatment Methods
• Flocculation/Sedimentation Flocculation refers to water treatment processes that
combine small particles into larger particles, which settle out of the water as sediment.
• Ion Exchange Ion exchange can be used to treat hard water. It can also be used to
remove arsenic, chromium, excess fluoride, nitrates, radium, and uranium.
• Adsorption Organic contaminants, color, and taste- and odor-causing compounds can
stick to the surface of granular or powdered activated carbon (GAC or PAC). GAC is
generally more effective than PAC in removing these contaminants. Adsorption is not
commonly used in public water supplies.
• Disinfection (chlorination, ozonation) Water is often disinfected before it enters the
distribution system to ensure that dangerous microbes are killed. Chlorine, chloramines,
chlorine dioxide, ozone
Approaches to mitigating contamination &
• Monitoring & Planning
• Source water protection
• Treatment & Remediation