Transport and Removal of Cryptosporidium Oocysts in Porous Media

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Transport and Removal of Cryptosporidium Oocysts
in Porous Media

• M. Elimelech et al.
• Environmental Engineering Program
• Yale University

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Outline

• Introduction
• Materials and Methods
• Results and Discussion
• Capture Mechanisms
• Conclusion

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Cryptosporidium parvum

• Protozoan pathogen
• About 4 ?m diameter
• Oocyst wall surrounding sporozoites
• Resistant to disinfection

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Riverbank Filtration
Tufenkji et al. EST, 2002
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Riverbank Filtration
Tufenkji et al. EST, 2002
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Objectives

• To investigate the physical and chemical factors
  governing the transport and adhesion of
  Cryptosporidium parvum in saturated porous media
• To compare the transport behavior of C. parvum to
  colloidal latex particles of comparable size

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Cryptosporidium in Column Experiments

• Obtained from Parasitology Laboratory at
  University of Arizona
• Stored in refrigerated 0.01 Tween 20 and
  antibiotic solution
• Concentration of 105 oocysts/mL

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Experimental Set Up
Syringe
Pump
Quartz Sand L 7.1 cm e 0.43 dc 210 mm
Microscopy Analysis
Fraction Collector
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Fluorescent Microscopy Analysis
Cryptosporidium sample from fraction collector
Filter Apparatus
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Particle Characterization

• Cryptosporidium
• 4 mm
• DAPI stained after column run
• Density about 1.05 g/cm3
• Zeta Potential -30 to -17 mV

• Latex
• 4.1 mm
• Carboxyl-modified
• Yellow-green dye
• Density 1.055 g/cm3
• Zeta potential
• -60 to -40 mV

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Zeta Potentials
pH ? 5.7
3.16
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Cryptosporidium Breakthrough Curves 1 mM
pH 5.6-5.8 Flow Rate 2 mL/min
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Cryptosporidium Breakthrough Curves 3.16 mM
pH 5.6-5.8 Flow Rate 2 mL/min
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Cryptosporidium Breakthrough Curves 10 mM
pH 5.6-5.8 Flow Rate 2 mL/min
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Cryptosporidium Breakthrough Curves
pH 5.6-5.8 Flow Rate 2 mL/min
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Latex Particle Breakthrough Curves
pH 5.6-5.8 Flow Rate 2 mL/min
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Cryptosporidium and CML Latex Breakthrough
Comparison
Cryptosporidium
Latex
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Mechanisms Straining
pH 5.6-5.8 Flow Rate 2 mL/min CML Particles
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Mechanisms Straining
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Mechanisms Ionic Strength EffectsCryptosporidium
Deposition Rate
3.16
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DLVO Interaction Energy Profile for
Cryptosporidium
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DLVO Interaction Energy Profile for
Cryptosporidium
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Radial Stagnation Point Flow System
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Relevance of Stagnation Point Flow System
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Stagnation Point Flow Resultsfor C. parvum
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Primary Deposition inStagnation Point Flow System
Field of view 100 mm
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Secondary Minimum Deposition in Stagnation Point
Flow System
Field of view 100 mm
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Conclusions

• Removal mechanisms in riverbank filtration
  settings can include physical straining
• Dependency on ionic strength determines the
  degree of removal.
• This removal is due to secondary minimum
  entrapment

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Acknowledgements

• US EPA