1. Image adapted from www.water4people.org

2. Arsenic Remediation in Bangladesh/Nepal:
The 3-kalshi Method vs.
The Arsenic BioSand Filter vs.
Well head removal
Stephanie Arbelovsky
Andrea Hektor
Christina Hynes
(team typhoidfun)

4. Overview Arsenic in Bangladesh 3-kalshi Method
Arsenic Biosand Filter (ABF)
Well-head removal
Pteris vittata
Conclusion

5. Contamination: Timeline
Pre-1970: Microbial contaminated surface water
1970: 2.5 million tubewells drilled
1990: 95% of population dependant on groundwater
1993: Widespread arsenic contamination
60% of wells above WHO guideline (10 ppb)
30% of wells above Bangladesh guideline (50 ppb)

6. THE 3-KALSHI METHOD

7. Construction 3 kalshis Stand (steel or bamboo) Course/Fine sand
Wood charcoal
Iron filings
Synthetic fabric
Photo courtesy Susan Murcott

8. Computer image courtesy Sandia National Laboratories
Removal processes
Zero-valent iron
Arsenate (V) / Iron Oxides
Precipitation
Arsenite (III) / Fe (II) FeAsO4 , also AlAsO4
Adsorption
Arsenate (V) / Fe(OH) 3
Filtration
Computer image courtesy Sandia National Laboratories

9. Effectiveness Khan’s Study: Hurd’s Study:
As(III) removal from 800 ppb to less than 2 ppb
Final As(total) concentration less than 10 ppb
Hurd’s Study:
As(total) removal from 215 ppb to 4 ppb

10. Flow rate 3 L water/day for adults recommended
3-kalshi provided L/day (Khan)
Efficiency decreases with increased flow rate
Inconsistencies in the literature

12. Advantages Inexpensive, locally manufactured materials
Point-of-use technology
Uses existing tubewell infrastructure
Easy to construct and operate

13. ARSENIC BIOSAND FILTER

14. Arsenic BioSand Filter (ABF)
A household-level drinking water filter developed at MIT to simultaneously remove arsenic & pathogens from tubewell water.
3-month pilot study (Sep 2002 to Jan 2003) conducted in Nepal
Evaluated performance of filter under various conditions
Investigated long-term removal efficiencies
Improved filter design
Implemented filters in arsenic-affected villages

15. Integration of 2 Removal Units
Arsenic Removal Unit
Metal Diffuser Box, Iron Nails, and Polyester Cloth
Pathogen Removal Unit
Sand and Gravel Layers
. . . So, Why Iron Nails??
Ferrous hydroxide (iron rust) is an excellent absorbent for arsenic
Surface complexion reaction occurs when aqueous arsenic species come into contact with ferrous hydroxide

16. How Does Arsenic Removal Work??
Iron nails rust when exposed to air and water
Arsenic absorbed to ferrous hydroxide (FH) particles
Some arsenic loaded FH particles trapped by polyester cloth
Most settle on top of fine sand layer

17. ABF Manufacturing
Can be entirely constructed with locally available materials and local labor
Concrete ABF’s were constructed by International Buddhist Society
Metal diffuser boxes manufactured in a metal shop in Kathmandu

18. ABF Installation Materials needed:
A concrete ABF (including metal box and lid
2 bottles of Piyush
A locally manufactured calcium hypochlorite solution used initially to disinfect the filter
2.5 L gravel (above 6-15 mm grain size)
Can be collected from local river
2.5 L sand (1-6 mm grain size)
~30 L of fine sand (less than 1 mm grain size)
1 piece of polyester cloth (30 by 30 cm)
5 kg iron nails

19. ABF Cleaning Remove metal box
Scrape top 2 cm of fine sand layer by hand
Remove top layer of water with small container
Replace with arsenic-free water
Repeat process several times
Replace metal box and lid

20. Results AFB found to be effective removing:
Arsenic: 85 – 96%, mean 93%
Total Coliform: 0 - >99%, mean 58%
E. coli: 0 - >99%, mean 64%
Iron: >90 - >97%, mean >93%

21. Users Liked. . . High flow rates (~14 L/hr) Simple operation
Minimal maintenance
Clean-looking, good tasting water
Think that the ABF is a durable, permanent solution to their drinking water problems!!

22. WELL HEAD REMOVAL

23. Larger Scale Treatment
Starting in 1998, Bengal Engineering College has installed in the Parganas and Nadia regions.
Initial installation costs Rs. 50,000 ($1250), but can provide water for two to three hundred households.
Utilizes activated alumina to adsorb arsenic.
Column lasts 10 to 15 years, but must be regenerated with caustic soda every 4 months.

24. Alumina found to be most effective, cost-efficient method of removing arsenic.
Arsenic sludge generated in a 4-month period amounts to less than 2 liters of sludge.
Requires no electricity.
Villagers understand basic operating principles of the units, and collectively help with day-to-day operations.
Tradition/routine of pumping water is not disturbed.
In all 8 locations, families pay approximately Rs. 50 per month for maintenance and operating costs. The poor are exempt.

26. Pteris vittata: Plant Technology?
Fern native to Asia and Africa. Commonly called Chinese Brake Fern.
Can remove arsenic directly from water in a process called phytofiltration.
Also able to hyperaccumulate arsenic from the soil. Generally around 22,630 mg of arsenic per kilogram of dry fern shoots/fronds.
In phytofiltration, arsenic water concentrations of 200 micrograms/liter by 100-fold in 24 hours.

27. Squeezing sap from the plants in a press removes ¾ of the arsenic in the plant. This arsenic can then be used for industrial purposes.
Researchers determining feasibility/safety of burning plants for fuel.

28. Further Research Further study on flow rate / efficiency relationship
Lifetime of the system
Cheaper
Increased arsenic removal

29. Final Thoughts Tubewell investment Perception of threat Cost
Testing capability
Few researchers, extrapolated ideas