1. G. Rincon, E. La Motta Civil & Environmental Engineering Kinetics of the Electrocoagulation of Oil and Grease Guillermo J. Rincon, Ph.D. Student Enrique J. La Motta, Ph.D., P.E. THE SOUTHEAST SYMPOSIUM ON CONTEMPORARY ENGINEERING TOPICS (SSCET) New Orleans, October 26, 2012

2. Civil & Environmental Engineering Disclaimer All the laboratory equipment and instruments, including the proprietary bench-scale reactor, utilized in this research, are property of the University of New Orleans and where purchased by this institution prior to the conception of this research. It is not the authors’ intention to support, advertise, criticize or disqualify the design, performance and/or use of any of these equipment and instruments. G. Rincon, E. La Motta

3. Civil & Environmental Engineering Outline  Tracer tests on a bench-scale reactor  Electrocoagulation of oil and grease  Kinetics of electrocoagulation (reaction order and rate coefficient)  Reactor modeling and models comparison G. Rincon, E. La Motta

4. Civil & Environmental Engineering Background Electrocoagulation  Generation of coagulants in- situ by dissolving aluminum or iron electrodes.  Contaminants in wastewater react chemically and/or attach to colloidal particles generated at the anode.  Flocs are removed by flotation, sedimentation and/or filtration. G. Rincon, E. La Motta

5. Civil & Environmental Engineering Background  Electrocoagulation (EC) was first proposed in England in 1889.  EC with iron and aluminum electrodes was patented in the U.S. in 1909.  Applied in large scale in the U.S for the first time in 1946.  Electrochemical wastewater treatment technologies have regained importance in the past two decades. G. Rincon, E. La Motta

6. Civil & Environmental Engineering Background  No information on the kinetics of EC process was available.  Research on EC of oil and grease is taking place at the University of New Orleans.  Experimentation has been done using a proprietary bench-scale EC reactor.  Removal of Hexane Extractable Materials (HEM) by EC with Al and/or Fe electrodes has been proved highly effective (>95%).  Deficient reactor performance indicated possible design flaws. G. Rincon, E. La Motta

7. Civil & Environmental Engineering Objectives  To identify design flaws in the EC reactor.  To generate Residence Time Distribution (RTD) data for the EC reactor.  To establish the kinetics of the EC process.  To propose a model for the EC reactor. RTD data + Kinetics + Model = Performance Prediction G. Rincon, E. La Motta

8. Civil & Environmental Engineering Experimental Plan  Perform tracer tests using different reactor configurations and fluid velocities to obtain RTD data.  Conduct EC experiments using synthetic oily wastewater  Perform reactor modeling using both the dispersion model and the TIS model.  Data analysis and interpretation of results. G. Rincon, E. La Motta

9. Civil & Environmental Engineering Laboratory Equipment EC Reactor Reactor Cell G. Rincon, E. La Motta

10. Civil & Environmental Engineering Experimental Set-Up Rotation of electrode plates changes the fluid’s path of flow through the reactor. G. Rincon, E. La Motta

11. Civil & Environmental Engineering Experimental Set-Up Tracer test set-up EC experiments set-up G. Rincon, E. La Motta

12. Civil & Environmental Engineering Data Acquisition Step-Input tracer test output G. Rincon, E. La Motta

13. Civil & Environmental Engineering Data Acquisition EC experiment output G. Rincon, E. La Motta

14. Civil & Environmental Engineering Results Effect of slot orientation on RTD in an 8-cell reactor with Q=0.5 L/min Effect of slot orientation on RTD in an 8-cell reactor with Q=1.0 L/min G. Rincon, E. La Motta

15. Civil & Environmental Engineering Results Effect of fluid velocity on RTD in an 8-cell reactor with horizontal slots. Effect of fluid velocity on RTD in an 8-cell reactor with vertical slots. G. Rincon, E. La Motta

16. Civil & Environmental Engineering Results Summary of RTD data G. Rincon, E. La Motta

17. Civil & Environmental Engineering Results Data points fitting by linear regression using ideal PFR first-order kinetics G. Rincon, E. La Motta

18. Civil & Environmental Engineering Results k’= 0.0441 s -1 R 2 =0.974 Fraction remaining vs. k’t curve using the dispersion model G. Rincon, E. La Motta

19. Civil & Environmental Engineering Results Fraction remaining vs. k’t curve using the TIS model n = 8.1 k’= 0.0443 s -1 R 2 =0.970 G. Rincon, E. La Motta

20. Civil & Environmental Engineering Results Comparison of fraction remaining curves for different models G. Rincon, E. La Motta

21. Civil & Environmental Engineering Conclusions  Electrocoagulation with aluminum electrodes is highly effective for HEM removal from stable emulsions and follows first-order reaction kinetics.  Electrocoagulation of oil and grease follows first order reaction kinetics. Therefore, PFR is the best type.  The reactor configuration used in this research allows easily changing the contact time.  Both the dispersion model and the tanks-in-series model correlate the experimental data very well (R 2 = 0.970).  The TIS model offers a simpler approach to modeling this type of reactors. G. Rincon, E. La Motta

22. Civil & Environmental Engineering Conclusions  Ninety-degree rotation of the electrode plates has a significant effect on the reactor’s performance.  Stagnant water, and pockets of hydrogen gas are the main operating problem with horizontal slots.  These problems increased when the flow-through velocity decreased below 0.032 m s -1.  Changing slot orientation increases the reactor average detention time by 50% and the HEM removal efficiency by 14%. G. Rincon, E. La Motta

23. Civil & Environmental Engineering Recommendations  More research on the kinetics of the electrocoagulation of HEM is needed.  Performing experiments under different operational conditions (wider range of flow rates and HEM concentrations, different current intensities, and electrode materials).  This reactor must be operated with fluid velocity higher than 0.032 m s -1 and following a horizontal path (slots oriented vertically).  For any reactor design and operational conditions, tracer tests must be performed in order to identify potential anomalies in flow pattern behavior. G. Rincon, E. La Motta

24. Questions?