Low Cost Design of Arsenic Removal from Groundwater in Bangladesh

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Low Cost Design of Arsenic Removal from
Groundwater in Bangladesh

• Kevin Banahan Jeremy Kozub Jesse Amsel
• Wentworth Institute of TechnologyEnvironmental
  Engineering CapstoneSpring 2005

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Overview of Arsenic problem

• Reliance on Surface Water
• Shift to Wells in early 70s
• 8-12 Million Wells
• 35-77 million people in regions where some wells
  are known to be contaminated
• Maximum concentration recommendation by WHO is
  10ug/L
• Maximum concentrations in Bangladesh 50ug/L

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Arsenic Pollution Mechanisms

• Arsenic is released by oxidation of pyrite
• Arsenic sorbed to minerals by over application of
  fertilizer
• Anoxic conditions allow iron oxyhydroxides
  release sorbed arsenic to solution

(8FeOOH CH3COO- 15H2CO3 ? 8Fe2 17HCO3-
12H2O)
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Theory of Arsenic Removal
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Chemistry of arsenic removal from groundwater by
sorption

• Synthetic groundwater composition
• H2O As(III) CaCl2 MgCl2 KCl
• Chloride ions will oxidize Arsenite (As III) to
  Arsenate (As V) in the presence of atmospheric
  oxygen

• H3AsO4 Fe(OH)3 ? FeAsO4.2H2O H2O

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Our Design Considerations

• Low cost
• Simple to make
• Easy to use
• Constructed of local materials
• Takes advantage of native labor

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5 Stage Model
Client Statement

• Problem Definition

• Conceptual Design

• Objectives
• lt50 ppb
• User Requirements
• Family Scale
• Easy to use
• Constraints
• Transport of water

• Design Specifications
• Sorption Isotherms
• Retention time
• Alternatives
• Tea-bag sorbent sack
• Loose sorbent
• Adapted column

• Verification of analytical method
• Refine process to synthesize groundwater
• Saturation experiments
• Regeneration experiments

• Documentations
• Analytical method
• Synthetic groundwater creation method
• Daily laboratory activities
• Experimental data

• Refine chosen design
• Optimize chosen design
• Scale model construction
• Test and evaluate design

• Completion of final design report
• Conclusions
• Suggestions

To develop a low-cost treatment system for the
removal of Arsenic from groundwater in Bangladesh

• Preliminary Design

• Detailed Design

Design Communication
Final Design
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Conceptual Design
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Sorbent Kinetics
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Breakthrough Curve
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Detailed Design
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Effect of Particle Size on Sorption
Parts per Billion of Ingestible Arsenic (Initial
Concentration 400 ppb)
Arsenic Mass Partitioning
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Column Experiments

• Objective
• Determine Sorptive Capacity in a bench-scale
  treatment unit

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Sorption
Material Balance to Determine Sorptive Capacity
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Column Breakthrough
Sorption Curve for Raw Sorbent
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Bangladeshi Technology Transfer
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Recommendations for further work

• Full-scale pilot study
• 10-15 cm diameter about 10 kg of sorbent.
• Model everyday use for a week.
• Soaking scheme for regeneration.
• Lab studies using native materials
• Bamboo, safi cloth

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Acknowledgments

• Dr. Jack Duggan (Design Advisor)
• Dr. Seth Frisbee (Stakeholder)
• Wentworth Professors Larry Decker, Francis
  Hopcroft and Henderson Pritchard for technical
  assistance

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Thank you