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Low Cost Design of Arsenic Removal from Groundwater in Bangladesh

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    Notes on slide 1

    -Before gaining independence the people of Bangladesh used surface water for all of their needs. -Water was contaminated with microbes that caused everything from diarrhea and Colera - Department of Public Health (DPH) and United Children’s Fund (UNICEF) -in the 80’s the goal of providing 80 % population well water was surpassed - 8-12 million wells were drilled to provide microbial safe drinking water -90% of the Bangladesh population of 130 million prefer to drink well water -Mid 1990’s was when the Arsenic Problem first hit the Radar Painted wells Safe and unsafe wells -The max allowable concentrations of 50 ug/L was lowered to 10 ug/L in 1993 - In New Jersey the allowable concentration will be lowered to 5 ug/L in 2006

    -There are Different opinions -1.) Arsenic is released by oxidation of pyrite in the sediments as the aquifer drawdown permits atmospheric oxygen to invade the aquifer ( Pyrite is a sink for not a source for Arsenic ) When the wells are pumped the oxygen from the air oxidized the pyrite and the arsenic is released… -2.) Arsenic sorbed to aquifer minerals are displaced into solution by exchange of phosphates from over application of fertilizer to surface soils -3.) anoxic conditions permit reduction of iron oxyhydroxides (FeOOH) and release sorbed arsenic to solution FeOOH - Ferric Oxide CH 3 COO - Acetate H 2 CO 3 – Carbonic acid HCO 3 – Bicarbonate H 2 O - Water

    Groundwater composition 1 L synthetic groundwater = 0.132 mL As(III) +0.188 g CaCl 2 + 0.255 g MgCl 2 + 0.012 g KCl Model of groundwater samples taken from wells in Bangladesh Very important to have chlorine ion’s present because it coverts arsenite to arsenate in the presence of atmospheric oxygen Arsenite (AsIII) = H 3 AsO 3 Arsenate (AsV) = H 3 AsO 4 Arsenic as As(V) is easier to remove Arsenate reacts with iron oxide (in crushed sorbent material) and sorbs to the surface of the crushed sorbent material leaving only clean water to filter through

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

    Client Statement – to develop a low-cost treatment system for the removal of Arsenic from groundwater in Bangladesh Problem Definition – Clarify Objectives - <50 ppb Establish User Requirements – family scale, easy to use Identify Constraints – transport of the water Establish Functions – adsorption system Conceptual Design – Establish Design Specifications – isotherms, retention time Generate Alternatives – tea bag, loose sorbent, column Preliminary Design – Model or analyze design Validation of analytical method - HACH kit Refining synthetic groundwater creation Saturation experiments – write up’s Regeneration experiments – write up’s Detailed Design – Choose a design to experiment with Refine and optimize design Construct scaled design Test and evaluate design Design Communication – Documentation – analytical method, groundwater creation, lab activities, experiments Final Design – Final report Interpretation of data Specifications for suggested design

    10 g of sorbent with 75 ml increments of 132 ppb arsenic groundwater

    Sorbent Material has 2 dominant sizes. 50 sieve size particles Retained Fines Fines have much higher surface area to mass ratio which may greatly influence the sorptive capacity.

    The use of Plastic hosing, stands, beakers, metal screen was for lavatory accuracy.. The column may be modified using these materials Safi Cloth- used from a filter, it can be folded so the fabric fibers cross and create a very fine screen Clay pots could be used (maybe a Spick-it) to feed the water into the top and catch the water at the bottom of the column.

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    Low Cost Design of Arsenic Removal from Groundwater in Bangladesh - Presentation Transcript

    1. Low Cost Design of Arsenic Removal from Groundwater in Bangladesh Kevin Banahan | Jeremy Kozub | Jesse Amsel Wentworth Institute of Technology Environmental Engineering Capstone Spring 2005
    2. Overview of Arsenic problem
      • Reliance on Surface Water
      • Shift to Wells in early 70’s
      • 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
    3. 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 + CH 3 COO- + 15H 2 CO 3 -> 8Fe 2+ +17HCO 3 - + 12H 2 O)
    4. Theory of Arsenic Removal
    5. Chemistry of arsenic removal from groundwater by sorption
      • Synthetic groundwater composition =
      • H 2 O + As(III) + CaCl 2 + MgCl 2 + KCl
      • Chloride ions will oxidize Arsenite (As III) to Arsenate (As V) in the presence of atmospheric oxygen
      • H 3 AsO 4 + Fe(OH) 3  FeAsO 4 .2H 2 O + H 2 O
    6. Our Design Considerations
        • Low cost
        • Simple to make
        • Easy to use
        • Constructed of local materials
        • Takes advantage of native labor
    7. Client Statement
      • Problem Definition
      Final Design
      • Conceptual Design
      • Preliminary Design
      • Detailed Design
      Design Communication 5 Stage Model To develop a low-cost treatment system for the removal of Arsenic from groundwater in Bangladesh
      • Objectives
        • <50 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
      • Refine chosen design
      • Optimize chosen design
      • Scale model construction
      • Test and evaluate design
      • Documentations:
        • Analytical method
        • Synthetic groundwater creation method
        • Daily laboratory activities
        • Experimental data
      • Completion of final design report
      • Conclusions
      • Suggestions
    8. Conceptual Design
    9. Sorbent Kinetics
    10. Breakthrough Curve
    11. Detailed Design
    12. Effect of Particle Size on Sorption Arsenic Mass Partitioning Parts per Billion of Ingestible Arsenic (Initial Concentration = 400 ppb) Aqueous Suspended Solids Settled Solids 70 185 Rinsed Sorbent 40 400 Sorbent w/ fines settled mixed  
    13. Column Experiments
      • Objective
      • Determine Sorptive Capacity in a bench-scale treatment unit
    14. Sorption Material Balance to Determine Sorptive Capacity mg/g 0.009 mass/mass sorptive capacity g 38 Mass Sorbent mg 0.344 Mass Sorbed L 2 Volume Treated mg/L 0.128 Final Conc mg/L 0.3 Initial Conc
    15. Column Breakthrough Sorption Curve for Raw Sorbent
    16. Bangladeshi Technology Transfer
    17. 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
    18. Acknowledgments
      • Dr. Jack Duggan (Design Advisor)
      • Dr. Seth Frisbee (Stakeholder)
      • Wentworth Professors Larry Decker, Francis Hopcroft and Henderson Pritchard for technical assistance
    19. Thank you

    + Kevin BanahanKevin Banahan, 2 months ago

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