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Cadmium Adsorption by Mixed-Culture Biofilms under Metabolizing and Non-Metabolizing Conditions

This study explores the adsorption of cadmium by mixed-culture biofilms under different metabolic conditions. The research investigates the impact of live and dead biofilm growth on acetate consumption and cadmium adsorption. Results indicate differences in cadmium uptake based on bacterial metabolic activity, highlighting the importance of bacteria viability in adsorption processes.

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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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