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, O 3 –Expensive, no residual protection, and oxidizes organics – toxic Chlorine dioxide, ClO 2 –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 – C , , 14, 17, 18, 20, 22, 37, , 45, , 52, 53, 71, 78