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Cadmium adsorption by mixed- culture biofilms under metabolizing and non- metabolizing conditions Jose Roberto Diaz University of Puerto Rico at Mayaguez.

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Presentation on theme: "Cadmium adsorption by mixed- culture biofilms under metabolizing and non- metabolizing conditions Jose Roberto Diaz University of Puerto Rico at Mayaguez."— Presentation transcript:

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: 1.biofilm growth, metabolically active 2.biofilm growth, metabolically inactive

8 To waste Experimental method Acetate Feed = 16mM Phosphate buffer with g CH 3 COOK (10 g/L acetate) to provide acetate as the electron donor Continuous flow packed bed reactor Q = 1mL/min Retention time of 60 min Air N2N2 reactor is inoculated with Mishawaka activated sludge Biofilm Growth Air is humidified to provide O 2 as the electron acceptor

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

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

11 Live or Dead? metabolically active metabolically inactive Live-Dead staining ImageLive CountDead CountRatio (L:D) average stdev ImageLive CountDead CountRatio (L:D) average stdev3.3676

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13 Acetate Consumption (live)

14 Acetate Consumption (dead)

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16 average % Cd adsorption =

17

18 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

19 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

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

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


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