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

• Bathing

• Toilets

• Cleaning

• Food preparation

• Cooling

• Fire protection

• Industrial purposes

• Drinking water = Potable water

©iStockphoto.com

Water Supply System

II. Water Sources and Treatment

• Water Cycle

• Groundwater

• Surface water

• Treatment

• How do these vary in different countries?

Water Cycle

Sources of Water

Aquifers (Groundwater)• Primary source of drinking water

• Porous consolidated rock or

unconsolidated soil

• Groundwater fills spaces

• Wells and pumps used to remove

water

Aquifer

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 Reserved

Sources of Water

Surface Water • Lakes, reservoirs, rivers

• Rivers dammed to create reservoirs

• Reservoirs store water during heavy

rain/snow

Courtesy NASA http://www.ghcc.msfc.nasa.gov/surface_hydrology/water_management.html

Courtesy USDA http://www.ks.nrcs.usda.gov/news/highlights/2006_april.html

Lake Tuscaloosa Dam

©iStockphoto.com

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

Water Treatment

• Amount of treatment

depends on quality of the

source

• Ground water requires less

treatment than surface

water

The city of Salem water treatment facility withdraws water from the North Santiam River.

Courtesty USGS http://pubs.usgs.gov/fs/2004/3069/

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.

• Filtration

• 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 & managing supply

• Monitoring & Planning

• Source water protection

• Education

• Treatment & Remediation