Water& Water Purification

Water

• Expands when freezing – fish • Liquid at room temperature – H-bonding• High specific heat (heat capacity) ↑ - weather • High heat of vaporization – cooling ↑• High surface tension – capillary act.↑• An excellent solvent (polar)

– Sometimes good?– Sometimes bad?

Water

• Covers 72% of the earth’s surface– Average of 2.5 miles deep

• 97.6% of all water is in the oceans

• 2.07% is in ice caps and glaciers, etc

• .5% is in groundwater (.28% above 1 km)

• .009% is in fresh lakes and rivers

• .005% is in soil moisture

• .008% is in the atmosphere

Hydrologic Cycle

• 4350 billion gallons/day fall on contig. US

• 3100 billion gallons/day ↑– By evaporation– By transpiration ?

• Plants giving off water – Oak tree 110 gal/day, acre of corn 3000 gal/day

• 800 billion gal/day ↓ to oceans and groundwater

• Leaves 450 billion gal/day for our use

Water Use

• In 1900 use was 40 billion gal/day

• In 1993 use was more than 400 billion gal/day

• Today? Constantly growing and water is being reused.

• World Resources Institute – by 2025, 3.5 billion people will experience water shortages.

Aquifers (groundwater)

• In US we were removing 90 billion gal/day– Source and demand are out of balance– Ogallala Aquifer stretches from SD to TX

• Was 58 ft thick in 1930• Was 8 ft thick in 1990

• Recharging – inject treated sewage water back into aquifers drinking water is coming out of.– El Paso, TX 10 million gal/day

Aquifer Depletion

• Causes subsidence – San Joaquin Valley– More than 40 ft

• Causes sink holes – south east – more damage

• Causes sea water encroachment – both coasts

Water Pollution

• What is in pure water?

Water Pollution

• What is in pure water?

• What is clean water?– Depends on use– Some pollution is natural– Most of the worst is man-made

• Clean Water Act – 1977 – responsibility on the wastewater producer

Chlorination

• Oxidizes the cell walls of water-borne bacteria– Started in early 1900’s– Deaths from typhoid, cholera, paratyphoid,

and dysentery decreased from 35/100,000 in 1900 to 3/100,000 in 1930

• Also reacts with trace organics → chlorinated hydrocarbons (THM’s)– 50% - 100% increased risk from cancer

(rectal, colon, bladder)– Why use?

Other options

• Most common chlorination – HOCl – hypochlorous acid – chlorination of HC’s

• Can use ozone, O3

– Expensive, no residual protection, and oxidizes organics – toxic

• Chlorine dioxide, ClO2

– Less toxic organics, chlorite and chlorate ions are troubling

• Ultraviolet light, UV, - complications

20 million/year die in underdeveloped countries from water-borne diseases

Solar stills in Mexico

H30 – C13

• 1 - 6, 8 - 11, 14, 17, 18, 20, 22, 37, 41 - 43, 45, 47 - 49, 52, 53, 71, 78