Desalination and Water Purification Research and Development Program Report No. 163 Aluminum Electrocoagulation and Electroflotation Pretreatment for Microfiltration: Fouling Reduction and Improvements in Filtered Water Quality U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado September 2014 Form Approved REPORT DOCUMENTATION PAGE OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From - To) September 2014 Final October 2010 – September 2014 5a. CONTRACT NUMBER 4. TITLE AND SUBTITLE Aluminum Electrocoagulation and Electroflotation Pretreatment for 5b. GRANT NUMBER Microfiltration: Fouling Reduction and Improvements in Filtered Water Quality 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Shankar Chellam, Principal Investigator Neranga 5e. TASK NUMBER P. Gamage, Graduate Research Assistant Charan Tej Tanneru, Graduate Research Assistant 5f. WORK UNIT NUMBER Mutiara Ayu Sari, Graduate Research Assistant 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER University of Houston Department of Civil and Environmental Engineering 4800 Calhoun Road Houston,, TX 77204-4003 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) Bureau of Reclamation 6th Avenue and Kipling Street Reclamation Building 67, Room 152 11. SPONSOR/MONITOR'S REPORT NUMBER(S) Denver, CO 80225 Tel: (303) 445-2248 12. DISTRIBUTION/AVAILABILITY STATEMENT 13. SUPPLEMENTARY NOTES Report can be downloaded from Reclamation Web site: https://www.usbr.gov/research/dwpr/DWPR_Reports.html 14. ABSTRACT Aluminum electrocoagulation and electroflotation pretreatment of surface water from Lake Houston significantly alleviated microfiltration (MF) membrane fouling in bench-scale experiments. Electrochemical aluminum production quantitatively obeyed Faraday’s law with a 3-electron transfer at nearly 100% efficiency resulting in precipitation of predominantly amorphous Al(OH)3. Enmeshment of colloids in amorphous precipitates (sweep flocculation) was the predominant colloid destabilization mechanism with secondary contributions from adsorption and charge neutralization. Fouling of a commercially available polymeric microfilter following electrocoagulation pretreatment was found to (i) be lower at pH 6.4 compared with 7.5, (ii) decrease only up to an intermediate aluminum dosage, and (iii) exacerbate with increasing transmembrane pressure. Cathodic evolution of hydrogen bubbles over relatively long durations was empirically observed to induce floc flotation. Electroflotation was also employed for MF pretreatment by skimming off the surficial floc layer and drawing water from near the bottom of the electroflotation cell. This approach significantly increased MF permeate flux reducing both the cake mass and the cumulative hydraulic resistance. Nanofilter flux decline was best controlled by combined pretreatment using electroflotation – MF. Also, viruses were effectively removed by electrochemical treatment with insignificant inactivation. Sweep flocculation was the primary virus destabilization mechanism. Highly encouraging laboratory-scale results point to the need for larger-scale evaluations of a hybrid electrofiltration/electrocoagulation-MF process for drinking water treatment. 15. SUBJECT TERMS Electrocoagulation, Electroflotation, Pretreatment, Microfiltration, Fouling, Virus removal, Surface water treatment 16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON OF ABSTRACT OF PAGES Saied Delagah a. REPORT b. ABSTRACT a. THIS PAGE 19b. TELEPHONE NUMBER (Include area code) U U U SAR 303-445-2248 Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Desalination and Water Purification Research and Development Program Report No. 163 Aluminum Electrocoagulation and Electroflotation Pretreatment for Microfiltration: Fouling Reduction and Improvements in Filtered Water Quality Prepared for the Bureau of Reclamation Under Agreement No. R10AP81218 by Shankar Chellam, Principal Investigator Neranga P. Gamage, Graduate Research Assistant Charan Tej Tanneru, Graduate Research Assistant Mutiara Ayu Sari, Graduate Research Assistant Department of Civil and Environmental Engineering University of Houston Houston, TX 77204-4003 U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado September 2014 MISSION STATEMENTS The U.S. Department of the Interior protects America’s natural resources and heritage, honors our cultures and tribal communities, and supplies the energy to power our future. The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Disclaimer The views, analysis, recommendations, and conclusions in this report are those of the authors and do not represent official or unofficial policies or opinions of the United States Government, and the United States takes no position with regard to any findings, conclusions, or recommendations made. As such, mention of trade names or commercial products does not constitute their endorsement by the United States Government. Acknowledgments The research reported herein was made possible by grants from the U.S. Bureau of Reclamation’s Desalination and Water Purification Research and Development Program (Cooperative Agreement No. R10AP81218), the National Science Foundation (CBET-0966939), and the Texas Hazardous Waste Research Center. The contents do not necessarily reflect the views and policies of the sponsors nor does the mention of trade names or commercial products constitute endorsement or recommendation for use. The authors wish to express their appreciation for the advice and assistance of Mr. Saied Delagah, Dr. Katharine Dahm, Mr. Frank Leitz, and Ms. Yuliana Porras-Mendoza from the Bureau of Reclamation. We are grateful to Dr. Ying Wei and her staff at the City of Houston’s East Water Purification Plant for facilitating sampling and water quality analyses. Will Payne assisted with the conduct of nanofiltration experiments. Peter Eriksson of GE Power & Water generously donated nanofiltration membrane samples. CONTENTS Page Executive Summary ................................................................................................ 1 Background and Introduction ................................................................................. 2 Conclusions and Implications ................................................................................. 7 Objectives and Approach ...................................................................................... 13 Experiments .......................................................................................................... 16 Source Water ................................................................................................... 16 Electrocoagulation .......................................................................................... 18 Microfiltration ................................................................................................. 19 Backwashing ................................................................................................... 20 Nanofiltration .................................................................................................. 21 Floc Physical Characteristics .......................................................................... 21 Microscopy ..................................................................................................... 23 Surface Charge ................................................................................................ 23 Powder X-Ray Diffractometry ........................................................................ 24 X-Ray Photoelectron Spectroscopy ................................................................ 24 ATR-FTIR....................................................................................................... 24 Aluminum Measurement ................................................................................ 25 Iron measurement............................................................................................ 25 Nanofilter Contact Angle ................................................................................ 25 Staining for Acidic Polysaccharides ............................................................... 26 Virus Growth and Enumeration ...................................................................... 26 Results and Discussion ........................................................................................