EFFECTS OF BLOOM-FORMING ALGAE ON FOULING OF INTEGRATED MEMBRANE SYSTEMS IN SEAWATER DESALINATION BY DAVID ALLEN LADNER B.S., New Mexico Institute of Mining and Technology, 2003 M.S., University of Illinois at Urbana-Champaign, 2005 DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering in Civil Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2009 Urbana, Illinois Doctoral Committee: Professor Mark M. Clark, Chair Associate Professor Eberhard Morgenroth Professor Steve Granick Dr. Kishore Rajagopalan, Illinois Sustainable Technology Center ABSTRACT Combining low- and high-pressure membranes into an integrated membrane system is an effective treatment strategy for seawater desalination. Low-pressure microfiltration (MF) and ultrafiltration (UF) membranes remove particulate material, colloids, and high-molecular-weight organics leaving a relatively foulant-free salt solution for treatment by high-pressure reverse osmosis (RO). An integrated membrane system is severely challenged, however, when an algal blooms occurs. This research investigated important factors for and mechanisms of fouling by bloom-forming algae in integrated membrane systems. In order to study RO fouling by algae, bench-scale testing protocols were evaluated. A method was developed to measure concentration polarization and intrinsic membrane permeability in a single experimental test. This laid the groundwork for accurately measuring flux decline from fouling. Natural seawaters (not under the influence of algal blooms) did not cause flux decline through buildup of organic foulants even though organic matter did deposit on the membranes. Significant deposition of algae and algogenic organic matter (AOM) was observed on RO membranes. Dissolved AOM caused little flux decline, but when particulate material was present the flux declined by ten percent over 24 hours. The organic-matter cake layers that formed on the membrane surface caused some resistance to flow, but it was small compared to the intrinsic membrane resistance. Modeling showed an interplay between two fouling mechanisms: cake-enhanced concentration polarization (CECP) and hydraulic resistance. For foulant cakes with low porosity and small particle size, hydraulic resistance may be more important than CECP. Foulant deposition on RO membranes was greatly affected by the feed spacer but was also affected by the shape of the permeate carrier. A permeate carrier with a fine mesh resulted in more spatially homogeneous foulant deposition and lower fouling propensity from AOM. A coarse permeate carrier caused foulants to deposit in a pattern defined by the feed spacer and flux decline was exacerbated. It is suggested here that both the feed spacer and the permeate carrier are important in determining the hydrodynamics that lead to foulant deposition. ii Unlike RO membranes, low-pressure microfiltration (MF) and ultrafiltration (UF) membranes were severely fouled by algae. Pore blocking was the dominant mechanism for the early stages of MF and cake filtration dominated during later stages as irreversibly blocked pores became unavailable. Cake filtration was the dominant mechanism in UF where the pores were smaller and foulants were excluded. Hydrodynamic shear applied to algal cells was detrimental to low-pressure filtration because of the release of highly-fouling organic matter. The highly fouling fraction was material large enough to be retained on a 0.22-μm microfilter but small enough that it was not removed by centrifugation or coarse (glass fiber) filtration. The algal cells themselves did not fall within this fraction since they were easily removed by centrifugation, but particulate material derived from broken algae did fall into the highly fouling fraction. Bacteria were also included in the highly-fouling fraction and were shown to be a major factor in fouling during an algal bloom. Adsorption of dissolved AOM was not a significant fouling mechanism on the hydrophilic membranes used here that are similar to the most common full-scale low-pressure membranes. iii To Miriam and Isaac iv ACKNOWLEDGMENTS “No man is an Iland, intire of it selfe; every man is a peece of the Continent, a part of the maine.”1 I am the latest data point that supports this long-standing hypothesis; many people have contributed support and guidance for the work represented by this document. First and foremost, I thank my advisor Mark M. Clark for the trust he has placed in me over the last several years. He gave me the freedom to work in the manner I saw fit and gave me encouragement and guidance. In moments of discouragement he knew just what to say to get me back on the horse. More important than knowledge, Mark helped me gain experience, for which I am grateful. My fellow graduate students provided great advice, thoughtful conversation, and quite a bit of food (at the office and in their homes). Manish Kumar and Won-Young Ahn are two fellow PhD students in the Clark research group to whom I will look up for the rest of my career. Other office mates were Adrienne Menniti, Kim Milferstedt, Katie Thompson, Li Liu, Xinyu Zhang, Fangqiong Ling, Nick Wiehardt, Sean Poust, Michelle Marincel, and Fabian Itel. Office #4125 was a great place to be because of these friends. Melvin Koh, Angela Koh, and Susana Kimura weren’t lucky enough to be in #4125, but they did work in lab #4124 and I appreciate them, too. Shaoying Qi, manager of the Environmental Engineering labs kept everything running smoothly on the fourth floor and was the first source of help with equipment; along the way he became a good friend. Marvis Orzek knew answers to all my department-related questions and taught me a great deal about go-cart racing. Steve Daley is an amazing financial officer. Sue Lowry and Bobby Vance make an excellent ordering and reimbursing duo. Kathy Hepler sorted out many administrative fellowship issues. One’s quality of life is highly dependent on the quality of people who surround them; my quality of life at Newmark Civil Engineering Laboratory was high. Undergraduate students working with me were Nathan Lester, Paul St. Aubyn, Derek Vardon, Esvina Choo Mei Seng, and John Jurevis. On one hand they eased my dish-washing burden, and on the other they did important work I could not have 1 Donne, John. 1624. Meditation XVII in Devotions upon Emergent Occasions. v performed myself. I wish them the best in their future careers and I hope I’ve had a positive impact on their view of Environmental Engineering. Collaborators at MWH are thanked for their help in securing research funding and designing experiments to make them relevant to real-world problems. Manish Kumar first served in that capacity then Arun Subramani took over. Samer Adham led the group during our collaboration. I am continually amazed at how willing people are to answer questions and provide support when I call them to ask for help, even when they are unrelated to the project. Robert Cheng and Tai Tseng from Long Beach Water Department supplied a seawater sample. Jess Brown and Chance Lauderdale from Carollo Engineers collected a red-tide phytoplankton sample. Gary Kirkpatrick at the Mote Marine Laboratory provided useful information about phytoplankton culture methods. Further culture information was given by Robert Andersen at the Provasoli-Guillard National Center for Culture of Marine Phytoplankton. Timothy Selle of Dow-Filmtech, Russ Steinhilber of Millipore, Rich Franks of Hydranautics, and Peter Hover of Koch supplied membranes. Bill Mickols of Dow-Filmtech provided helpful conversations about concentration polarization. Peter Eriksson of GE helped troubleshoot my membrane setup. There are certainly others who I’ve forgotten who patiently answered my phone calls and provided advice. The first funding source for this project was obtained through the United States Department of the Interior, Bureau of Reclamation, Desalination and Water Purification Research and Development Program, assistance agreement #05FC811169. Additional support was provided through the United States Environmental Protection Agency, Science to Achieve Results (STAR) fellowship program. The WateReuse Foundation funded grant number WRF-06-014 to MWH on which the University of Illinois was a subcontractor. Lastly, the AWWA Research Foundation (now the Water Research Foundation) supported this work under funding agreement 04201. My doctoral committee is thanked for their input and patience. They do not realize how much the short conversations I had with them have remained on my mind and steered my thinking. They are Eberhard Morgenroth, Kishore Rajagopalan, and Steve Granick. vi My family is the reason I am here. My dad, Kenneth Ladner, taught me how to do unit conversions and an innumerable array of other practical, useful things. My mother Kathy Ladner gave me a home environment where I could flourish mentally and physically. My siblings Carol Roth and Bryan Ladner are my continual friends. Lastly, but most importantly, I must thank my wife, Miriam Nibley Ladner. My life with her began at the same time my PhD program began. She stayed with me when her formal education finished so that I could finish mine. Now she is the mother of our beautiful son, Isaac. Research is great, but Miriam makes my life complete. vii TABLE OF CONTENTS 1 INTRODUCTION....................................................................................................... 1 2 LITERATURE REVIEW .......................................................................................... 4 2.1 MEMBRANE FOULING ..................................................................................... 4 2.1.1 Cake-enhanced concentration polarization ................................................. 6 2.2 ALGAL BLOOMS AND MEMBRANE FOULING ........................................... 8 2.2.1 Marine algal blooms ................................................................................... 8 2.2.2 Industry experience with algal fouling ....................................................... 9 2.2.3 Algal fouling laboratory studies................................................................ 11 2.2.4 Effects of shear on algal fouling ............................................................... 12 2.3 STUDYING FOULING AT THE BENCH SCALE ........................................... 13 2.3.1 Low-pressure membrane testing ............................................................... 13 2.3.2 High-pressure membrane testing .............................................................. 13 2.4 FIGURES ............................................................................................................ 17 3 EXPERIMENTAL MATERIALS AND METHODS............................................ 18 3.1 REVERSE OSMOSIS ......................................................................................... 18 3.1.1 Bench-scale RO testing apparatus ............................................................ 18 3.1.2 Test Configurations ................................................................................... 19 3.1.3 Membranes ................................................................................................ 21 3.1.4 Algal fouling experiments......................................................................... 21 3.2 MICROFILTRATION AND ULTRAFILTRATION ......................................... 21 3.2.1 Dead-end cell setup ................................................................................... 21 3.2.2 Membranes ................................................................................................ 22 3.3 SEAWATER ....................................................................................................... 23 3.4 ALGAL CULTURE ............................................................................................ 24 viii 3.5 ANALYTICAL METHODS ............................................................................... 24 3.5.1 Algal and bacterial enumeration ............................................................... 24 3.5.2 Flow cytometry ......................................................................................... 26 3.5.3 Bulk fluorescence...................................................................................... 27 3.5.4 Ultraviolet absorbance .............................................................................. 27 3.5.5 Total organic carbon ................................................................................. 27 3.5.6 Carbohydrates ........................................................................................... 28 3.5.7 Proteins ..................................................................................................... 29 3.5.8 Size-exclusion chromatography ................................................................ 29 3.5.9 Visual image analysis of fouled membranes ............................................ 29 3.5.10 Laser-scanning cytometry ......................................................................... 30 3.5.11 Infrared spectroscopy ................................................................................ 30 3.5.12 Scanning electron microscopy .................................................................. 31 3.5.13 Atomic force microscopy .......................................................................... 31 3.6 TABLES .............................................................................................................. 32 3.7 FIGURES ............................................................................................................ 33 4 BENCH-SCALE EVALUATION OF REVERSE OSMOSIS .............................. 36 4.1 EVALUATION OF TEST CONFIGURATION OPTIONS............................... 37 4.1.1 BaIReMT .................................................................................................. 37 4.1.2 Transient recovery .................................................................................... 39 4.1.3 Full recycle................................................................................................ 40 4.1.4 Comparison of configurations ................................................................... 40 4.2 TRANSPORT PARAMETER DETERMINATION .......................................... 42 4.3 OSMOTIC PRESSURE DETERMINATION .................................................... 44 4.4 SEAWATER FRACTIONATION EXPERIMENT ........................................... 46 ix 4.5 TRANSPORT PARAMETER RESULTS .......................................................... 47 4.6 SEAWATER FRACTIONATION RESULTS ................................................... 49 4.7 SEAWATER SOURCE COMPARISON ........................................................... 50 4.8 CONCLUSIONS REGARDING BENCH-SCALE TESTING .......................... 52 4.9 TABLES .............................................................................................................. 55 4.10 FIGURES ............................................................................................................ 56 5 REVERSE OSMOSIS FOULING BY MARINE ALGAE ................................... 70 5.1 DESIGN OF EXPERIMENTS ............................................................................ 71 5.2 FLUX DECLINE CAUSED BY ALGAE .......................................................... 72 5.3 AOM CHARACTERIZATION .......................................................................... 72 5.4 FOULED MEMBRANE AUTOPSY .................................................................. 74 5.4.1 Visual and fluorescence image analysis ................................................... 74 5.4.2 Scanning electron microscopy .................................................................. 76 5.4.3 Infrared spectroscopy ................................................................................ 77 5.5 FOULING MECHANISMS ................................................................................ 78 5.6 CONCLUSIONS REGARDING REVERSE OSMOSIS FOULING BY AOM 85 5.7 FIGURES ............................................................................................................ 88 6 LOW-PRESSURE MEMBRANE FOULING BY MARINE ALGAE ................ 99 6.1 FOULING BY DIRECT ALGAL FILTRATION ............................................ 100 6.2 EFFECTS OF SHEAR ON LOW-PRESSURE MEMBRANE FOULING BY ALGAE ..................................................................................................................... 103 6.2.1 Shearing .................................................................................................. 103 6.2.2 Cell breakup characterization ................................................................. 105 6.2.3 MF/UF experiments for testing shear effects .......................................... 107 6.2.4 Size fractionation .................................................................................... 107 6.2.5 Determination of the level of shear ......................................................... 109 x