POU Arsenic Removal

1. POU Arsenic Removal Team DHMO Justin Ferrentino Barry Schnorr Haixian Huang David Harrison

2. Arsenic in Bangladesh

3. Background • Historically, drinking water was primarily taken from surface water • Open dug wells • Ponds • Rivers • High population density  disease • diarrhea, dysentery, typhoid, cholera and hepatitis

4. Arsenic Concentrations in Water Districts of Bangladesh/India

5. Wells • In the past 30 years, programs have provided safer drinking water with wells • 8-12 million shallow tube-wells • Reduction in waterborne disease • Well water was the preferred water source • Approximately 90% of Bangladesh’s 130 Million served by wells

6. Arsenic • 1993, Arsenic discovered in Bangladesh groundwater • Arsenic is naturally occurring in geological formations under Bangladesh • British Geological Survey in 1998 • >70% of shallow tube wells (in 61 of 64 districts) had [As] > 10 ppb • 27% had [As] > 50 ppb • estimated that 28-35 million exposed to [As] above 50 ppb and 46-57 million exposed to [As] above 10 ppb Well marked with red X due to Arsenic contamination

7. Effects • Most common disease result is skin lesions • Skin and internal cancer rates are expected to rise over the next decade

8. Options • Providing low arsenic groundwater • Safe shallow groundwater • Deep (>200 m) aquifers • Rain water harvesting • Pond sand-filtration • Household chemical treatment • Piped water from safe/treated sources

9. Chemical Treatment Technologies • Common methods • Oxidation & co-precipitation • Alum addition • Adsorption to media • Activated carbon, iron & manganese coated sand • Ion exchange and membrane techniques • Membrane filters (Reverse Osmosis)

10. Bucket Treatment Unit • Oxidize in one bucket, filter in another • Red / Green buckets (Bangladesh well code) • Collect As(V) on alum, FeCl3, Fe2(SO4)3 , other Fe compounds

11. Red Bucket: Oxidation • Oxidizing agent: 2 mg/L KMnO4 • Color and safety issues • Color removed in filter? • Alternative oxidants: CaCl2O2, aeration • Adsorption of As(V) • Naturally occurring Fe removal • Can also disinfect

12. Red Bucket: Co-precipitation • Add packet, mix with stick • DHPE-Danida unit: 30-60 s mixing and 90 s gentle stirring recommended • Settling for 1-2 hours • Stevens Institute Unit: Settling in filter bucket

13. Green Bucket: Filtration • Sand filter bed • Sometimes inside cloth filter • Needs washing 1-8 times/month • Where does As go? • Bacterial growth in filter bed

14. Oxidation • Oxidation of arsenite [As (III)] to arsenate [As (V)] with potassium permanganate (KMnO4) • As (V) is 60 times less toxic than As (III) • As (III) occurs in non-ionized form • Use 2 mg/L of KMnO4 for aluminum coagulation and 1.4 mg/L for iron

15. Coagulation and Co-precipitation • Aluminum coagulation -use 200 mg/L of aluminum sulfate [Al2(SO4)3]to form Al-As complex • Iron coagulation -use 100 mg/L of ferric chloride (FeCl3) or ferric sulfate [Fe2(SO4)37H2O] to form Fe-As complex

16. Aluminum vs. Iron • For arsenic concentration < 1000 ppb both resulted in > 90% removal • For arsenic concentration > 1000 ppb, ferric salts were found to be better than aluminum sulfate • Ferric salts are effective over a wider pH range Iron: pH of 6.0- 8.5 Aluminum: pH of 7.2-7.5

17. A Temporary Solution • Bucket treatment must be a temporary solution, not a permanent one. • It creates toxic sludge that needs to be disposed of • The ultimate goal should be to connect people to a safe and sustainable water source

18. Alternative Solutions • Stop relying on groundwater. Use surface water. • Problem: Surface water is contaminated with fecal matter. • It is easier to treat water for fecal matter than for arsenic. Invest in treatment plants. • Use rainwater. Set up rainwater catchments. This is only a partial solution, because there is a 3-month dry season. • Dig surface wells, or drill deep aquifer wells - both are less likely than tubewells to become contaminated with Arsenic.

19. Current Developments in BTU • BTU’s are in demand and available all over Bangladesh and West Bengal. They cost $US 6.00. There are NGO programs that subsidize the cost for the very poor. • The WHO wants NGO’s, not foreign companies, to manufacture and install the BTU’s. • There are over 13000 BTU’s in Bangladesh and West Bengal, as of Dec 2000 [can’t find a more recent number]

20. References: • Alliance for Global Sustainability: http://www.eawag.ch/research_e/w+t/ags/web-UT/oben.html • WHO: http://www.who.int/mediacentre/factsheets/fs210/en/ http://www.who.int/water_sanitation_health/dwq/arsenic2/en/index3.html • “Rapid Assessment of Technologies for Arsenic Removal at the Household Level”, Sutherland et al. 2001, “An Overview of Arsenic Removal Technologies in Bangladesh and India”, M. Ahmed 2001 “Development of Low-cost Technologies for Removal of Arsenic from Groundwater”, Ali et al. 2001 All from: BUET-UNU International Workshop on Technologies for Arsenic Removal from Drinking Water • Groundwater Arsenic Contamination in Bangladesh and West Bengal, India:http://ehp.niehs.nih.gov/members/2000/108p393-397chowdhury/chowdhury-full.html • BBC Coverage: http://news.bbc.co.uk/1/hi/world/south_asia/252308.stm • Supply Chain Initiative: http://www.wsp.org/publications/sa_arsenic.pdf