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Cadmium adsorption by mixed-culture biofilms under metabolizing and non-metabolizing conditions

Cadmium adsorption by mixed-culture biofilms under metabolizing and non-metabolizing conditions. Jose Roberto Diaz University of Puerto Rico at Mayaguez August 3, 2006 Advisors: Dr. Robert Nerenberg Dr. Jeremy Fein Mentors: Leon Downing Brian Ginn. Outline. Introduction

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Cadmium adsorption by mixed-culture biofilms under metabolizing and non-metabolizing conditions

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  1. Cadmium adsorption by mixed-culture biofilms under metabolizing and non-metabolizing conditions Jose Roberto Diaz University of Puerto Rico at Mayaguez August 3, 2006 Advisors: Dr. Robert Nerenberg Dr. Jeremy Fein Mentors: Leon Downing Brian Ginn

  2. Outline • Introduction • Objectives • Experimental method • Results and discussion • Conclusions • Future work • Acknowledgements

  3. Introduction • Heavy metals are a common cause of pollution • non-degradable • accumulate in the environment • causes of land and water pollution • Conventional treatment methods increasingly expensive heavy metals in the atmosphere

  4. Introduction • microorganisms treat heavy metal-polluted wastes • accumulate trace levels of ions • major role in modification, activation and detoxification • Immobilized systems have higher surface areas and biological mass concentration • ability of mixed cultures to adhere • form biofilms • provide higher loading rates than suspended systems

  5. Introduction • Biofilms used in wastewater treatment systems • resistant to inhibitory and toxic metals • tolerant to high metal concentrations • high affinity for metallic cations • anionic nature of polymers inhibit entrance of cationic molecules to biofilm • Immobilized-cell bioreactor technology provides cost-effective means for eliminating pollutants

  6. Introduction • Live vs. Dead

  7. Objectives • Determine extent of Cd adsorption onto mixed-culture bacterial system under two conditions: • biofilm growth, metabolically active • biofilm growth, metabolically inactive

  8. Biofilm Growth Air is humidified to provide O2 as the electron acceptor Experimental method Acetate Feed = 16mM Phosphate buffer with 16.6356g CH3COOK (10 g/L acetate) to provide acetate as the electron donor Air N2 Q = 1mL/min Retention time of 60 min Continuous flow packed bed reactor To waste reactor is inoculated with Mishawaka activated sludge

  9. Bulk solution: • no ammonium • 2 ppm Cd • 70 ppm Acet (dead) • 150 ppm Acet (live) Cs-irradiation 35,000 rads/hr Experimental method Cd Adsorption divide to test tubes (5 mL each) add one-tenth of a gram of biofilm to each test tube mix for approximately 2 hours centrifuge and filter analyze samples Acetate by Ion Chromatography Cd in bulk liquid by ICP-OES

  10. Results and discussion • Live or Dead? • Acetate consumption • Cd Adsorbed

  11. metabolically active metabolically inactive Live-Dead staining Live or Dead?

  12. Acetate Consumption (live)

  13. Acetate Consumption (dead)

  14. average % Cd adsorption = 48.9928

  15. Discussion • bacteria are surviving the radiation treatment • Non-metabolizing bacteria are still consuming acetate in some samples more than others • Metabolizing bacteria seem to be adsorbing less Cd (≈27%) than samples that have non-metabolizing bacteria (≈49%) • possible reasons why

  16. Conclusions • Radiation treatment is not effective in killing bacteria and must be modified • Non-metabolizing bacteria certainly showed an effect on how much Cd was adsorbed • Samples with varying amounts of acetate adsorbed around the same percent of Cd for metabolizing and non-metabolizing bacteria

  17. Future work • Different method of killing bacteria • Non-metabolizing vs. metabolizing in suspended growth system • Different electron acceptors and donors for growing biofilm

  18. Acknowledgements • EMSI • Dr. Valli Sarveswaran • Leon Downing • Brian Ginn • Dr. Jeremy Fein • Dr. Robert Nerenberg • CEST

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