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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)
Contents of the Crisis
• Availability/Safety
• Sanitation
• Desalination
• Other factors
– Contamination
Availability/Safety
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
Percent of Population with Access
to Safe Drinking Water by
Country, 2000
Percent of Total Disease Burden
Caused by Unsafe Water by
Country, 2000
Renewable Freshwater Supply by
Country*, 2000
*m3 per person per year
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
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
Treatment
Sewage Treatment
Sewage Treatment
• Preliminary
– Filter/screen to remove solids and grit
– Solids and grit are washed and land-filled
Sewage Treatment
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
Sewage Treatment
Sewage Treatment
• Secondary
– Percolating filters
– Aeration tanks
– Biological waste from either treatment is
settled out
Sewage Treatment
Sewage Treatment
• Tertiary
– Kill bacteria
• Disinfect using chlorine/bleach
– Dechlorinate using sodium bisulfite or similar compound
• Reed beds, sand filters, grass plots
• UV light
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
Desalination
Desalination
• 7500 plants world wide
– 60% in Middle East
• Saudi Arabia produces 128 million gallons per day
– 12% in Americas
• Florida and Caribbean
Desalination Process
• Requires pre-treatment
– Chlorination
– Ozone
– UV light
– Stripping or scrubbing to remove Cl or O3
Desalination Processes
• 1-50 ppm solids
• Phase separation
• Higher Concentrations
• Mechanical separation
– Multiple Effect Distillation
– Reverse Osmosis
– Electrodialysis Reversal
• Sometimes paired with
membrane
– Multiple Stage Flash
• Flash at successively lower
• ~98% salt removal
• Used if ~2% of initial salt
pressures
– Mechanical Vapor
Compression
•
content allowable
Otherwise, further
separation required
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!!!
Why aren’t these used in Africa?
• Lack of education
• Lack of technology
• Lack of stable government
• Lack of funds
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
Contamination
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
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
Arsenic Decontamination
• 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
References
• http://www.world-wide-water.com/ - water treatment technical info/guide
• http://www.who.int/mediacentre/factsheets/fs210/en/ - World Health Org.;
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Bangladesh info
http://www.wateryear2003.org/en/ev.phpURL_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
Seawater Composition
Element
O
H
Cl
Na
Mg
S
Ca
K
Br
C
Au
% by mass
85.84
10.82
1.94
1.08
0.1292
0.091
0.04
0.04
0.0067
0.0028
less
Component
H2O
ClNa+
Mg2+
SO4,2Ca2+
K+
C inorganic
BrB total
Sr2+
F-
molality (mol/kg)
53.6
0.546
0.469
0.0528
0.0282
0.0103
0.0102
0.00206
0.000844
0.000416
0.000091
0.000068