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World Water Crisis: Availability, Safety, and Contamination

This article discusses the global water crisis, focusing on the availability and safety of water, sanitation issues, desalination as a solution, and factors contributing to contamination. It also highlights the impact of the water crisis on different countries and populations.

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World Water Crisis: Availability, Safety, and Contamination

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  1. World Water Crisis” ‘Water, water everywhere’ but what’s a brother gotta do to get a drink around here?” Joel Thomas CBE 555 November 27, 2007 Updated: Joel Thomas (F07) Original: Christie Dosch (F05)

  2. Contents of the Crisis • Availability/Safety • Sanitation • Desalination • Other factors • Contamination

  3. Availability/Safety

  4. Water Breakdown • 70% of Earth is H2O • 3% of H2O is freshwater • Of freshwater • 79% is glacial • 20% is groundwater • 1% is surface water • Of surface water • 52% is lakes • 38% is soil Moisture • 8% is atmospheric vapor • 1% in living organisms • 1% is rivers

  5. Percent of Population with Access to Safe Drinking Water by Country, 2000

  6. Percent of Total Disease Burden Caused by Unsafe Water by Country, 2000

  7. Renewable Freshwater Supply by Country*, 2000 *m3 per person per year

  8. Scarcity • Middle East • “Many of the wars of this [20th] century were about oil, but the wars of the next century will be about water” - World Bank Vice President Ismail Serageldin • Hebron, Palestine limited households to running water twice a month • Egypt will require an extra 20 million m3 to meet the needs of the growing population

  9. Quality • Only 60% of population of Africa has access to safe drinking water • In largest cities, < 10% have sewer connections • Increased preference for/reliance on well water • 2.3 billion people world wide suffer from diseases linked to dirty water • Contaminations • Biological – Poor Sanitation • Chemical/Mineral – Further Study of Arsenic in Bangladesh

  10. Treatment

  11. Sewage Treatment

  12. Sewage Treatment • Preliminary • Filter/screen to remove solids and grit • Solids and grit are washed and land-filled

  13. Sewage Treatment

  14. Sewage Treatment • Primary • Settling tanks (clarifiers) to remove remaining solids • Produces “sludge” containing 70% of initial solids • Sludge treated by digestion • Heat bacteria to optimal conditions • Produces methane • May be used as fuel • Remaining solids are cooled and used as fertilizer

  15. Sewage Treatment

  16. Sewage Treatment • Secondary • Percolating filters • Aeration tanks • Biological waste from either treatment is settled out

  17. Sewage Treatment

  18. Sewage Treatment • Tertiary • Kill bacteria • Disinfect using chlorine/bleach • Dechlorinate using sodium bisulfite or similar compound • Reed beds, sand filters, grass plots • UV light

  19. Assessing Potability • Biochemical Oxygen Demand (BOD) • Amount of O2 required by bacteria to oxidize organic material in 5 days • Drinking water < 1ppm • Raw sewage >> 100ppm

  20. Desalination

  21. Desalination • 7500 plants world wide • 60% in Middle East • Saudi Arabia produces 128 million gallons per day • 12% in Americas • Florida and Caribbean

  22. Desalination Process • Requires pre-treatment • Chlorination • Ozone • UV light • Stripping or scrubbing to remove Cl or O3

  23. 1-50 ppm solids Phase separation Multiple Effect Distillation Sometimes paired with membrane Multiple Stage Flash Flash at successively lower pressures Mechanical Vapor Compression Higher Concentrations Mechanical separation Reverse Osmosis Electrodialysis Reversal ~98% salt removal Used if ~2% of initial salt content allowable Otherwise, further separation required Desalination Processes

  24. Desalination Efficiency • City of Santa Barbara Desalination Plant • 8.2 MGD of brine • At 1.8 X the Salinity of Seawater • 6.7 MGD product • 1.7 MGD filter brine • 1.7-5.1 cubic yards/day of solids • ~40 percent water recovery!!!

  25. Why aren’t these used in Africa? • Lack of education • Lack of technology • Lack of stable government • Lack of funds

  26. Other Factors • Pollution • Water contaminated with toxic materials • Acid rain • Eutrophication – disrupts ecosystem • E.g. Phosphorus, Nitrogen from fertilizer • Global warming • Redistribution of water • Glaciers melting • Aquifers depleting

  27. Contamination

  28. Source of Contaminants • Underground injections wells • Landfills • Runoff from roads/agriculture • Leaks/spills in chemical storage or transportation (including septic, petroleum) • 1 L of gas contaminates 1 Million L of groundwater

  29. Arsenic Contamination • India • Bengal and Bangladesh (Ganges River area) • As high as 1.8ppm (EPA limit is 10ppb) • ~200,000 people dead from As poisoning

  30. Removal Adsorption with ferric oxide compound ppt with iron salts Nanofiltration MnO2 Coagulation Problems Removal is expensive Detection is difficult Field tests only detect above 0.05mg/L (the upper limit) Technology is not readily available Expensive Equipment Extensive Training Arsenic Decontamination

  31. References • http://www.world-wide-water.com/ - water treatment technical info/guide • http://www.who.int/mediacentre/factsheets/fs210/en/ - World Health Org.; Bangladesh info • http://www.wateryear2003.org/en/ev.php-URL_ID=4874&URL_DO=DO_TOPIC&URL_SECTION=201.html – African Situation • http://www.umich.edu/~gs265/society/waterpollution.htm - water distribution, usage, & pollution • http://ohioline.osu.edu/aex-fact/0768.html - treatment principles, regulations, & diagram • http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/SewageTreatment.html -Sewage treatment principles • http://www.coastal.ca.gov/desalrpt/dchap1.html - Seawater Desalination • http://www.nature.com/nature/focus/water/index.html - Global Water Crisis Articles • http://news.nationalgeographic.com/news/2000/07/0714_water.html - Water and Peace in the Middle East • http://answers.google.com/answers/threadview?id=34014 – Further Resources for Desalination (specifically charitable) • http://www.mwra.state.ma.us/03sewer/html/sewditp.htm - Detailed WW Treatment

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