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 Technology Environmental Engineering Capstone Spring 2005
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Low-Cost Design of Arsenic Removal from GroundwaterJeremy Kozub*, Kevin Banahan*, Jesse Amsel**Wentworth Institute of Technology, Environmental Engineering Program, Class of 2005 (Jack Duggan, Ph.D., P.E., faculty advisor)For this project, a student team designed and evaluated treatment alternatives for the removal of arsenic from groundwater used in developing countries. The application of sorption technologies was evaluated using bench-scale testing of a range of sorption materials, support media and differing contact geometries. Sorption capacity of treatment units were designed to accommodate the daily consumption of individual families using a community well in Bangladesh.Until the early 1990's, there was little awareness that groundwater in Bangladesh contained high levels of arsenic. The adverse health affects of chronic exposure to arsenic are well documented. Although current technologies to treat arsenic in groundwater exist, there are economic, social and cultural factors that prevent these technologies from being used in Bangladesh. This project focused on developing a low-cost alternative technology that could be readily assembled and implemented by local villagers.As a capstone project for the environmental engineering program at Wentworth of Technology, this project has been performed by three students under the supervision of a faculty advisor. Students applied previous coursework in the areas of economics, engineering theory and application, design, communication skills and ethical principles to complete this project. The project was performed in collaboration with external non-profit and non-governmental organizations. The goal of this project is to further develop the creation of a low-cost system that will become available to large populations of those in need.
Transcript of Low Cost Design of Arsenic Removal from Groundwater in Bangladesh
Low Cost Design of Arsenic Removal from
Groundwater in Bangladesh
Kevin Banahan | Jeremy Kozub | Jesse AmselWentworth Institute of Technology
Environmental Engineering Capstone
Spring 2005
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
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)
Theory of Arsenic Removal
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
Our Design Considerations
• Low cost
• Simple to make
• Easy to use
• Constructed of local materials
• Takes advantage of native labor
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
Conceptual Design
Sorbent Kinetics
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0.1 1 10 100 1000 10000
Retention Time (min)
Arsenic Concentration (ppb)
Breakthrough Curve
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Cumulative Groundwater Treated (ml)
Arsenic Concentration (ppb)
Detailed Design
Rinsed Sorbent
54% Settled Solids
17% Aqueous29%
Suspended Solids
Effect of Particle Size on Sorption
Arsenic Mass Partitioning
Aqueous
Suspended Solids
Settled Solids
Sorbent w/ fines
0% Settled 10%
Aqueous
90% Suspended
Solids
mixed settled
Sorbent w/ fines 400 40
Rinsed Sorbent 185 70
Parts per Billion of Ingestible Arsenic(Initial Concentration = 400 ppb)
Column Experiments
Objective
• Determine Sorptive Capacity in a bench-scale treatment unit
Sorption
Initial Conc 0.3 mg/L
Final Conc 0.128 mg/L
Volume Treated 2 L
Mass Sorbed 0.344 mg
Mass Sorbent 38 g
mass/mass sorptive capacity
0.009 mg/g
Material Balance to Determine Sorptive Capacity
Column Breakthrough
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0 50 100 150 200
Pore Volumes (1 pore volume = 11.4ml)
Effluent Concentration
(ppb Arsenic)
Sorption Curve for Raw Sorbent
Bangladeshi Technology Transfer
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
Acknowledgments
• Dr. Jack Duggan (Design Advisor)
• Dr. Seth Frisbee (Stakeholder)
• Wentworth Professors Larry Decker, Francis Hopcroft and Henderson Pritchard for technical assistance
Thank you
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