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

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

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

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

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

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

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

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.

Charge vs pH for As

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

Problem Solution

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

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!

Schematic of UW column photo-oxidation

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

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

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?

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

Bibliography Cullen, W. R., and Reimer, K. J. (1989). Arsenic Speciation in the Environment. Chemical Reviews 89 (4), 713-764 Hug, Stephen et al. “Options for safe drinking water at the household level.” EAWAG. [1/27/07]. http://www.eawag.ch/research_e/w+t/ags/websoras/websoras.html Leupin, Olivier. “The Arsenic Crisis.” Alliance for Global Sustainability. [1/26/07]. http://www.eawag.ch/research_e/w+t/ags/index.html McArthur et al. “Arsenic in groundwater: testing pollution mechanisms for sedimentary aquifers in Bangladesh.” [1/26/07]. http://www.es.ucl.ac.uk/research/lag/as/pdf/Arsenicpaper.pdf 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), 517-568.