Groundwater Arsenic Occurrences inBangladesh and Mitigation Options

Kazi Matin Ahmed, PhDDepartment of Geology

University of DhakaDhaka, Bangladesh

kmahmed@du.ac.bd

Goldschmidt2015Prague, CZ, 16-21 August 2015

Groundwater as the Sources for Drinking & Irrigation Water

Map of Arsenic Occurrence1998-99 Survey1998-99 Survey 2002-03 Survey2002-03 Survey

Over 5 million wells tested!Most severely affected

areas are in the southern part of the deltaic plains

Some contamination in the north east, northwest is least contaminated

Hills in the southeast safe

Distribution is controlled by surface geology

Deeper wells are mostly safe

Geology and Arsenic Distribution

Basin Model

Conceptual Model of Arsenic Distribution in the Bengal Basin

I : Source Area

- Erosion and transportation dominant

- Detrital sulphides and/or oxides

- Oxidation & dissolution of sulphides

- Precipitation of ferric hydroxide

- Adsorption of As.

III : Distributary Channels & Swamps

- Sedimentation dominant, abundant detritus

- Locally brackish water

- Strongly reducing - dissolution of oxyhydroxides anddesorption of arsenic

- Diagenetic pyrite

- Fe & As to solution

IV : Estuarine / Marine Environment

- Saline water- Arsenic transferred to oceans

II : Braided & Meandering Channels

- Alternating deposition and resuspension.

Channels :oxidising - precipitation of hydroxides and adsorption of As.

Point barsreducing - dissolution of oxyhydroxides and desorption of arsenic

- Iron rich coatings- Separation of SO 4 from Fe and As.

Impact of Arsenic on Rural Water Supply

Source: WaterAid Bangladesh

Possible Impacts on Rice Production

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2

4

6

8

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0 10 20 30 40 50 60 70

Soil-As (mg/kg)

Rice

Gra

in Y

ield

(ton

s/he

ctar

e)

50% reduction

‘Parrot beak’

Duxbury et al

Number of People with Skin Lesions

• Surveys identified around 30,000 having arsenical skin lesions

• Overall prevalence is about 1 in 1000, however, local studies reported much higher numbers;

• Argoss et al - double mortality rate due to CVD for exposure in access 150 ppb; Wasserman et al reported reduced intellectual development of kids.

• Alan Smith predicts 1 in 100 dying of cancer at 50 ppb, and 1 in 10 at 500 ppb

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READ-F MAGC/ALCANSono 45-25 Sidko

Arsenic Removal TechnologiesA –Household ARTs: Alcan, Nelima, Read F, Shawdesh, SonoB - Community ARTs: Sidko

Well Switching

Alternative Safe Water Options

Deep Tube Wells

(GOB, 2002)

Rural Piped Water Systems

(GOB, 2002)

Subsurface Arsenic Removal

Number of People Exposed to >50 ppb

GOB, 2002

GOB/UNICEF 2009 MICS

• The results of the Multiple Indicator Cluster Survey (MICS) in 2009 estimated that approximately 22 million people were exposed to arsenic concentrations above 50 μg/L, and approximately 36 million above 10 μg/L.

• The results of the Multiple Indicator Cluster Survey (MICS) in 2013 estimated that approximately 19.6 million people were exposed to arsenic concentrations above the Bangladesh Drinking Water Quality Standard of 50 μg/L

http://www.unicef.org/bangladesh/knowledgecentre_6868.htm

Arsenic in BRAC WASH Area

Source: Nepal C Dey, Fazlul Karim and Sifat-E-Rabbi, 2013. Use of tubewell water for different purposes at household level: safety practices in rural Bangladesh, in Achievements of BRAC Water, Sanitation and Hygiene Programme Towards Millennium Development Goals and Beyond, Research Monograph Series No. 60, p11-31, Research and Evaluation Division (RED), BRAC.

Large Number of Untested Wells

176/357 wells49% untested

50% of households(53/105) knowingly drinkfrom unsafe well

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Possible Safe Water Options for Different Regions

Out of 19.0 million, 10.9 million people can be covered by Deep TW with No 6 or TARA hand pump

The rest 8.1 million people are to be covered by PSF, DW, AIRP etc

If well can be installed up to deep aquifer having gravel problem, nearly 5.7 million out of 8.1 million can be served with Tubewell

Concluding Remarks• Natural arsenic occurrence in the alluvial aquifer is and will remain Natural arsenic occurrence in the alluvial aquifer is and will remain

as a major challenge for water supply in Bangladesh ;as a major challenge for water supply in Bangladesh ;• A major public health concerns; thousands of patients with visible A major public health concerns; thousands of patients with visible

symptoms; likely impacts on food security; symptoms; likely impacts on food security; • A large number of mitigations options are available, DTW has been

the most effective one;• Still millions are exposed to arsenic above current BD limit (50 ppb),

number almost doubles if WHO provisional guide line value (10 ppb) is considered;

• Targeted efforts are necessary to provide safe water to all who are still drinking water having As above safe limits;

• Impacts of As on Irrigation and food security need special attention.

Thank you all!