1. Arsenic Groundwater Contamination-Bangladesh Encheng Zhou Xiaowen Kan

2. Introduction  Prior to the 1970s, the highest infant mortality rates in the world  UNICEF and the World Bank ‘s help(ground water well programme)  Over 8 million wells constructed  In 1993: Association of health problems with arsenic contamination.  Estimated 35 to 77 million inhabitants are at risk of drinking contaminated water.

3. Occurrence of arsenic in the world Bangladesh is not the only country with arsenic pollution of the groundwater, but pollution is exceptionally widespread here

4. Arsenic Contamination A metalloid element known for its toxicity and carcinogenicity 70 million people possibly at risk Still now, it is difficult to resolve the problem Country EffectedPopulation Effected Bangladesh60,000,000 Vietnam2,500,000 India1,000,000 China720,000 Taiwan200,000

5. Desorption from Fe(OH)3 Theories of Arsenic Mobilisation Mechanism of Mobilization Anthropogenic Sources Pyrit Hypothesis Industry: Pharm. Products, Mining Agriculture: Fertilizer, Pestizides Geogenic Mechanism

6. Pyrit Hypothese Pyrites minerals (FeAsS) are present in the delta sediments Due to the lowering of the water table (by intensified extraction for irrigation)  oxidation of pyrites deposits in so-called Vadose Arsenic adsorbs to Fe(OH)3 During recharge period  release of As (same mechanisms as before)

7. Health Effects Organ SystemProblems SkinSymmetric hyperkeratosis of palms and soles, melanosis or depigmentation, bowen's disease, basal cell carcinoma and squamous cell carcinoma. liverEnlargement, Jaundice, cirrhosis, non-cirrhotic portal hypertension Nervous SystemPeripheral neuropathy, hearing loss Cardiovascular SystemAcrocyanosis and Raynaud's Phenomenon Hemopoietic SystemMegalobastosis Respiratory SystemLung Cancer Endocrine SystemDiabetes mellitus and goiter Signs of arsenicosis: spots on the hands

8. Possibilities of Elimination For removal: oxidation of As(III) to As(V) is needed Principle mechanisms: oxidation; adsorption; ion exchange Oxidation: Oxidants such as O2 O3 KMnO4 H2O2 Mainly in industrialized countries. Coagulation & Adsorption - Bucket Treatment Unit: (1) Precipitation by metal salts in upper bucket (2) Coagulation by mixing (3) Adsorption by passing sand filter precipitation + sedimentation/ filtration; membrane filtration.

9. Conclusion The worst environmental catastrophe of the twentieth century. The government needs to conduct effective water Remediation techniques are available but are being limited Every effort should be made to help the people of Bangladesh