Chapter 9- water quality

Source water- untreated water used to produce drinking water

Finished water- the drinking water delivered to the distribution system after treatment, if any

Surface water- all water on the surface (lakes, rivers, reservoirs, ponds, and oceans) as distinguished from subsurface or groundwater

Groundwater- water that is contained in the interconnected pores of an aquifer

Aquifer- a section of earth or rock containing fresh water, known as groundwater (any water stored naturally underground or flowing through rock or soil, supplying springs and wells).

Examples of major salt lakes Caspian Sea, Dead Sea, and Great Salt Lakes

Hydrological (water) cycle: The natural cycle by which evaporates from oceans and other water bodies, accumulates as water vapor in clouds, and returns to oceans and other water bodies as precipitations

Renewable Water- water that is continuously replenished by the hydrological cycle for withdrawal within reasonable time limits; includes water in rivers, lakes, or reservoirs that fill from precipitation or runoff

Reservoirs- artificial lakes produced by constructing physical barriers across flowing rivers, which allow water to pool and be used for various purposes (Lake Winona)

Runoff- water originating as precipitation on land that then runs off the land and into rivers, streams, and lakes, eventually reaching the oceans, inland seas, or aquifers

Water withdrawal- removal of freshwater for human use from any natural source or reservoir, such as a lake, river, or aquifer. If not consumed, the water may return to the environment and can be used again

Water Scarcity- a country faces water scarcity when its annual supply of renewable freshwater is less than 1,000 cubic meters (264,000 gallons) per person

Water Stress- a country faces water stress when its annual supply of renewable freshwater is between 1,000 and 1,700 meters/per person (264,000-448,000 gallons) per year

4 Stages of Water Treatment:

Coagulation- aluminum sulfate is used to remove dirt and other suspended material in the water

Sedimentation- the mixture is transferred to sedimentation tanks where the heavy particles settle to the bottom and the clear water moves to filtration

Filtration- the water if filtered to remove smaller impurities- usually filters are made of layers of sand, gravel, and charcoal

Disinfection- water is treated with a disinfectant like chlorine to kill and bacterial or microorganisms

Fluoridation of water: some communities in the United States add fluoride to public drinking water in order to prevent tooth decay - field trials conducted in the 1940s demonstrated a 50-70% reduction in the prevalence of dential caries

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