Arsenic in Drinking Water

Presentation Outline Arsenic levels around the world Arsenic in the environment Background levels Health effects Mitigation options

Zheng Gong, MIT department of Civil and Environmental Engineering, August 2005 Over 30 countries in the world is affected by arsenic in drinking water

From the Journal of the National Cancer Institute (2007) “The impact of arsenic in drinking water on this large population is without precedent for environmental causes of human cancer, and it points to the public health priority of ensuring that arsenic concentrations in drinking water are controlled worldwide.” from “Fifty-Year Study of Lung and Bladder Cancer Mortality in Chile Related to Arsenic in Drinking Water”

“ The contamination of groundwater by arsenic in Bangladesh is the largest poisoning of a population in history …” “ The fundamental intervention is the identification and provision of arsenic-free drinking water.”

Source: WHO Synthesis Report on Arsenic in Drinking Water 2002 Arsenic in the Environment Naturally occurring metalloid element in the earth’s crust Released to the environment by natural pathways –volcanic emissions –biological activities –weathering reactions

Water SourceTypical baseline concentrations Atmospheric precipitation (rain and snow) Usually < 0.03 ug/L River waterUsually < 2 ug/L Lake waterUsually < 1 ug/L SeawaterUsually about 1.5 ug/L GroundwaterUsually < 10 ug/L Background Arsenic Levels

Guideline Value in Drinking Water WHO10 ug/L(ppb) = 0.01 mg/L (ppm) Australia7 ug/L Canada25 ug/L EU10 ug/L Japan10 ug/L USA10 ug/L Bangladesh50 ug/L Cambodia50 ug/L China50 ug/L India50 ug/L Lao50 ug/L Myanmar50 ug/L Nepal50 ug/L Pakistan50 ug/L Vietnam10 ug/L urban, 50 ug/L rural Source: World Bank. Towards a More Effective Operational Response. Volume

Iron Nitrates Hardness Alkalinity pH

Ingestion Drinking water Eating food containing high arsenic Dermal absorption Bathing in high arsenic water Handling arsenic contaminated substances Inhalation Breathing sawdust or burning smoke from wood treated with arsenic Living in areas with unusually high natural levels of arsenic in rock Usually major Usually minor Sources: US Agency for Toxic Substances and Diseases Registry (ATSDR) ToxFAQ for Arsenic. Accessed Sep 27, WHO Synthesis Report on Arsenic in Drinking Water 2002 Exposure Pathways

Source: Harvard University. “Harvard Arsenic Project.” Internet. Accessed Sep 27, Chronic Health Effects After melanosis, keratosis and other lesions may occur Keratosis is the hardening skin bulges on palms and feet

Halima’s Story After receiving a rainwater harvesting tank through an Arsenic Mitigation Program in Bangladesh, Halima’s symptoms of arsenicosis disappeared. Social Effects

Alternative Arsenic-Free Sources Arsenic Removal Technologies Safe tube wells Improved Dug wells Deep wells Rainwater harvesting Surface water treatment Arsenic Mitigation Mitigation Options

Diffuser Basin Lid Container Pipe Gravel Coarse Sand Water Fine Sand Iron Nails Brick chips Kanchan TM Arsenic Filter

Kanchan TM Arsenic Filter Biosand filter design adapted to remove a certain level of arsenic from water Add non-galvanized iron nails in the diffuser basin Nails will rust and adsorb arsenic onto the surface of the rusty nails

Arsenic Removal Process The iron nails quickly rust after contact with water and air. Iron rust (ferric hydroxide) is an excellent adsorbent for arsenic. When arsenic-containing water is poured into the filter, surface reactions with the iron occurs, and arsenic is rapidly adsorbed onto the surface of the rusty nails. The arsenic loaded iron particles are then flushed down by the water and trapped on top of the sand layer. The brick chips help to evenly disperse the water over the nails to allow for further absorption.

Filter Installation Iron Nails & Brick Chips Photos from Ngai et al, 2006

Bricks help ensure even water distribution and prevent the nails from moving. If iron nails are not protected by brick chips, then arsenic removal efficiency can decrease as water passes through the basin without contact with iron nails.