1 / 28

Transport of Viruses, Bacteria, and Protozoa in Groundwater

Transport of Viruses, Bacteria, and Protozoa in Groundwater. Joe Ryan Civil, Environmental, and Architectural Engineering Department University of Colorado, Boulder Environmental Engineering Seminar October 11, 2000. Acknowledgments. Students

aden
Download Presentation

Transport of Viruses, Bacteria, and Protozoa in Groundwater

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transport of Viruses, Bacteria, and Protozoa in Groundwater Joe Ryan Civil, Environmental, and Architectural Engineering Department University of Colorado, Boulder Environmental Engineering Seminar October 11, 2000

  2. Acknowledgments • Students • University of Colorado: Jon Loveland, Jeff Aronheim, Annie Pieper, Becky Ard, Robin Magelky, Jon Larson, Theresa Navigato, Yvonne Bogatsu • UCLA/Yale University: Jun Long, Ning Sun, Chun-han Ko • Collaborators • Ron Harvey, U.S. Geological Survey • Menachem Elimelech, Yale University • Funding • National Water Research Institute • U.S. Environmental Protection Agency • Laboratory Assistance • Chuck Gerba, University of Arizona • Joan Rose, University of South Florida • Field Assistance • Denis LeBlanc & Kathy Hess, U.S. Geological Survey

  3. Public Health Problem • Waterborne Disease Outbreaks • estimates for the United States • 1 to 6 million illnesses per year • 1000 to 10,000 deaths per year • only 630 documented outbreaks 1971-1994 • Milwaukee, Wisconsin, 1993 • Cryptosporidium, the “hidden germ” • about 400,000 illnesses, greater than 100 deaths • DNA evidence: human, not bovine, origin

  4. Public Health Problem • Waterborne Disease Outbreaks • acute gastrointestinal illness • short duration, “self-resolving” for most people • chronic, severe, fatal for some • infants and elderly • pregnant women • immuno-compromised • more serious illnesses • heart disease, meningitis, diabetes (coxsackie virus) • liver damage, death (hepatitus virus)

  5. Public Health Problem • Microbial Perpetrators • viruses • bacteria • protozoa • Where are they coming from? • groundwater (58%), surface water • point source, non-point source

  6. Viruses • Enteric • replicate only in gut • Size • 20 – 200 nm • Structure • protein capsid • RNA or DNA

  7. Viruses • Life Cycle • ingestion • drinking water • within the gut • adsorption • penetration • transcription • replication • assembly • host cell lysis • excretion from gut

  8. Bacteria • Enteric • grow in gut (only?) • Size • 0.5 to 2 m • Structure • cell walls • proteins • phospholipids, fatty acids • motililty • flagellae • cilia

  9. Bacteria • Life Cycle • ingestion • meat, vegetables, drinking water • within the gut • adsorption • penetration • growth • release of toxins • excretion from gut Vibrio Cholera adhering to rabbit villus E. coli adhering to calf villus

  10. Protozoa • Enteric • grow in gut only • Size • 3 to 12 m • Cyst Structure • rugged protective membrane • carries trophozoites

  11. Protozoa • Life Cycle • ingestion • drinking water • within the gut • excystation • parasitic growth • cyst formation • excretion from gut

  12. Occurrence in Groundwater • Viruses • 38% positive by PCR • 7% positive by cell culture • Bacteria • 40% positive for coliform bacteria • 50-70% positive for enterococci • Protozoa • 12% Giardia and/or Cryptosporidium(5% in vertical wells)

  13. Monitoring in Groundwater • Maximum Contaminant Level • coliform bacteria – 40 per liter • viruses – 2 per 107 L (proposed, GWDR) • Ground Water Disinfection Rule • will require disinfection unless “proof” of adequate “natural disinfection” • viruses nominated as target microbe • Virus Transport Models • predictions of travel time • attachment and inactivation

  14. Microbe Transport

  15. Microbe Transport • Transport equation dispersion advection equilibrium attachment/ release kinetic attachment/ release growth or inactivation/ “die-off”

  16. Microbe Attachment • Attachment • kinetic • colloid filtration • collision frequency  • collision efficiency  • release • first-order (kdet) • much slower than attachment • equilibrium • distribution coefficient • linear, reversible tracer concentration microbe time tracer concentration microbe time

  17. Microbe Attachment • Surface Chemistry • capsids, cell walls • carboxyl – RCOO- • amine – RNH3+ • net surface charge • usually negative • pHpzc ~3-4 • for viruses, pHpzc can be estimated from protein content of capsid

  18. Microbe Attachment • Porous Media Surface Chemistry • negative • quartz, feldspars, etc. • clay faces • positive • iron, aluminum oxides • clay edges • electrostatic interactions • favorable deposition sites • unfavorable deposition sites

  19. Microbe Attachment • Microbe Size • small • collisions caused by Brownian motion • large • collisions caused by settling • Microbe Density • Range 1.01 to 1.05 g cm-3 • collisions caused by settling

  20. Microbe Attachment • Optimal Size for Transport • about 1-2 m • bacteria • viruses collide by diffusion • protozoa collide by settling • protozoa also removed by straining

  21. Microbe Attachment • Target Organism • collision efficiency • about the same for all microbes • variation in  comes from porous media • collision frequency • favors bacteria • BACTERIA, but… • adhesion favored for growth • biofilms

  22. Virus Attachment • Bacteriophage PRD1 • Cape Cod field experiments • sewage-contaminated zone • uncontaminated zone • 100 L injections • multi-level samplers

  23. Virus Attachment • Transport favored in contaminated zone • PRD1 attachment sites blocked by sewage organic matter • collision efficiency  fraction of favorable deposition sites

  24. Microbe Growth/Inactivation • Growth • viruses – no replication outside gut • bacteria – growth possible, but unlikely • protozoa – no growth outside gut

  25. Microbe Growth/Inactivation • Inactivation • viruses – mainly temperature-dependent • bacteria – lysis? predation? • protozoa – generally resistant to disinfection, so inactivation is slow?

  26. Virus Inactivation • Viruses • inactivation in solution • first-order decay • inactivation on surfaces? • effect of strong attachment forces

  27. Virus Inactivation • Bacteriophage MS2 • Cape Cod sediment • 32P DNA • 35S protein capsid • rapid loss of infectivity • release of radiolabels

  28. Summary • Predicting microbe transport • less difficult for viruses, protozoa cysts • no growth, inactivation simpler • more difficult for bacteria • motility • adhesion behavior motivated by growth, nutrients • growth, die-off more complicated • Bacteria should be target organism (?) • least frequent collisions, motility • may be complicated by longer-term adhesion strategies

More Related