1. Arsenic Water Pollution in Bangladesh
Phoebe Stinson
CBE 555
1/29/07

2. Bangladesh Southeast Asia Population: 149,350,000 (7th in world)
Area: 55,600 sq mi (49th in world)
Ave Life Expectancy: 63 yrs old (3% >65 yrs)
GDP Per Capita- $2100

3. Water Tables
Defined as section where atmospheric pressure=water p below which ground is saturated with water

4. Arsenic Known toxin causing:
Diabetes mellitus
Cardiovascular problems
Cancer (skin, lung, liver, bladder, pancreas)
Sores
Knotty, blackened palms
Exists as arsenite, arsenate, arsenic, arsine
Former two found in water sources

5. The Problem 1/3 of pop. depend on groundwater above 50 ppb
(WHO Std- 10 ppb)
20 million already poisoned
Many don’t seek treatment
(mild to moderate)
Estimated 3000 deaths
annually

6. Cause of Problem 1970s- High population density
Pathogen rich surface water
250,000 children die annually of water-borne diseases
~40 million tube wells drilled
Infant mortality reduced
High arsenic ground water concentration

7. Cause of Problem
Arsenic on sediment- traveled in Ganges river from Himalayas
Copper Arsenite Pesticides
Entered aquifers via organic carbon (MIT)
Untreated waste at fault?
Some claim irrigation is at fault

8. Problem Solutions Oxidative Adsorption- Players As III & As V
Ratio Controlled by redox state
Unequal adsorption capabilities
As(V) dominates under oxidizing conditions
Oxidation Catalyst- UV
Oxidants- ClNaO, MnO4-, O3, etc.
Adsorbents- Sand, clay, charcoal, etc.

9. Charge vs pH for As

10. Problem Solution Oxidative Adsorption- Practical Example
Chemicals dangerous, expensive and difficult to use on household level
Alternative- Batch Process (SORAS)
Add lemon juice to open container of ground water, close, shake, leave in the sun and filter…
Any guesses as to what happens next???
Hint- think of other naturally occuring ions in water

11. Problem Solution

12. SORAS Results Lab Tests- 90% removal Field Tests- 45-80% Advantages
Dependent upon initial concentration
Advantages
Inexpensive
Safe
Convenient
Disadvantages
Inefficient
Low % of removal
Batches w/ small amounts of water being treated

13. As Removal With Sol-Gel Tech.
Photo-oxidation/Adsorption- Players
Adsorbent- Al2O3 sol
Oxidation Catalysts- UV, TiO2 sol
Process
Coat glass beads w/ Al2O3+TiO2 mixture
Pack 12” Column-110 s contact
Treat with UV radiation
Combines 2 steps into 1!

14. Schematic of UW column photo-oxidation

15. Sol-gel Process Results
*Overall As removal- ~93%
*As III removal~75%

16. Sol-gel Process Summary
Advantages
Very efficient
Continuous flow process
Disadvantages
Costly Start-up Materials
Need to build column for pyrex for correct wavelength transmission
Expensive sols and wasteful if not done properly
Slow flowrate

17. Questions Raised Is desorption possible on the media?
How often would shutdown be required to run desorption?
What would be the payback period?
Is there a cheaper, more safe alternative to sol-gel process?
Could SORAS process be made more efficient?

18. Thank You!
Thank you to Prof. Marc Anderson, Eunkyu Lee, PhD, and Kevin Leonard

19. Bibliography
Cullen, W. R., and Reimer, K. J. (1989). Arsenic Speciation in the Environment. Chemical Reviews 89 (4),
Hug, Stephen et al. “Options for safe drinking water at the household level.” EAWAG. [1/27/07].
Leupin, Olivier. “The Arsenic Crisis.” Alliance for Global Sustainability. [1/26/07].
McArthur et al. “Arsenic in groundwater: testing pollution mechanisms for sedimentary aquifers in Bangladesh.” [1/26/07].
Smith, R. M., and Martell, E. M. (1976). Critical Stability Constants. Plenum Press.
Smedley, P. L., and Kinniburgh, D. G. (2002). A review of the source, behavior and distribution of arsenic in natural waters. Applied Geochemistry 17 (5),