FAVORITE PAPERS: A NEW FEATURE FOR CONNECTIONS

We invite you to read an experimental first column of a novel idea. For each issue of Connections we will ask a handful of respected and experienced members of our community to name and comment upon those papers in the desalination literature which are their personal favorites. No, we are not asking for nominations of “best” or “most influential” papers, only their personal favorites. What papers have spoken to them or influenced their work, and why? Read on.

by Yehia M. El-Sayed and Robert S. Silver

Yehia M. El-Sayed and Robert S. Silver, 1980, “Fundamentals of Distillation,” in Principles of Desalination, 2nd ed., K. S. Spiegler and A. D. Laird, eds., Academic Press, New York, Chapter 2.

Nominated by: John H. Lienhard V, PhD, PE Department of Mechanical Engineering Massachusetts Institute of Technology lienhard@mit.edu

El-Sayed and Silver gave me an excellent introduction to thermodynamic analysis of seawater distillation systems and the rationale for multi-stage designs. I found the technical framework surprisingly accessible, and, after brief investigation, I was not surprised to discover that both authors were distinguished mechanical engineers. So, of course the approach made sense to me—they spoke in my native language. Robert S. Silver was the James Watt Professor of Mechanical Engineering at the University of Glasgow, a recipient of the ASME Heat Transfer Memorial Award, and renowned as one of the fathers of MSF technology. Yehia M. El-Sayed had conducted research at many universities (including MIT) and twice received the ASME Edward F. Obert Award for outstanding research in thermodynamics.

I have used this book chapter directly in my desalination class to teach mechanical engineering students about distillation and energy efficiency. El-Sayed and Silver point out the levers for raising the performance of distillation. First, try to minimize the entropy produced by heat transfer across temperature differences. Second, especially, avoid discarding exergy with the leaving streams. Multistage designs target the latter issue. In a multi-effect evaporator, heat released during condensation at one pressure drives evaporation in a lower pressure section, so that a given quantity of heat can distill vapor over and over again. In multi-stage flash distillation, liquid vaporizes as brine is throttled into successive stages, while the condensing vapor preheats counterflowing feed. The irreversibility of heat transfer across the evaporator stages of MEE is replaced by throttling irreversibilities in MSF.

The exergetic assessment of water/power coproduction, as discussed in this chapter, remains a topic of research today. Does thermal desalination have an advantage over RO from a primary energy perspective? The challenge in such an analysis is to correctly apportion the power loss that accompanies steam extraction. El-Sayed and Silver had the basic framing right, but they did not address the likelihood that extraction would change a turbine’s second-law efficiency. Under their inspiration, my group has recently looked at that question. Silver, in a separate work, noted that all of the wonderful thermodynamic innovation of MSF, addressing 99.9% of the feed, could “be rendered useless” by the mere 0.1% that forms scale on the heat exchangers. That, however, is another story.

About the nominator John H. Lienhard V is a Professor of Mechanical Engineering at MIT. He has worked on many desalination technologies, with a focus on thermodynamic efficiency and system assessment. His group’s seawater properties correlations have been used widely, and their seawater surface tension data is now an IAPWS international guideline. Lienhard has been issued 36 U.S. patents, has written three textbooks and hundreds of papers, and, like El-Sayed and Silver, has received ASME’s Edward F. Obert and Heat Transfer Memorial Awards.

Edo Bar-Zeev, Iliana Berman-Frank, Olga Gershevitz and Tom Berman, Proceedings of National Academy of Sciences, Vol 109, June 5, 2012, 9119-9124.

Nominated by: Harvey Winters, Ph.D. Department of Biological Sciences Fairleigh Dickinson University harvey@fdu.edu

This paper by Edo Bar-Zeev and co-authors proposed for the first time the term “protobiofilm” to represent a planktonic (free-floating) biofilm precursor before its attachment to a surface, like a reverse osmosis (RO) membrane. They further stated that the development of a protobiofilm, which is a complex of extracellular polymeric substances (EPS), like transparent exopolymer particles (TEP) with extensive microbial attachment, would jump-start biofilm development. The type of EPS in the protobiofilm, as suggested in the paper, was that of TEPs that were detected with use of a dye, alcian blue, which interacts with any organic substance that contains carboxyl or sulfated groups. This was the first time that someone had suggested that biofilms actually begins as a planktonic entity. This new paradigm intrigued me as neither my biofilm colleagues nor I had previously ever thought that biofilm formation actually began as a planktonic precursor to the attached biofilm.

For the last decade, TEP had been a serious topic for discussion as the source of biofilm formation on RO membranes since Tom Berman first introduced its concept. Since alcian blue is not specific for just TEP, it appears that Bar-Zeev and co-authors may have been implicating protobiofilms, rather than TEP, as the main cause of membrane biofouling. Protobiofilms and biofilms share common characteristics, except protobiofilms, are planktonic and biofilms attach to surfaces. The presence of protobiofilms in all types of RO feed water emphasizes their importance in enhancing the degree of biofilm formation.

The formation of protobiofilms suggests that it develops as bacterial aggregates, which are immersed in an EPS matrix, while in a planktonic state. Aggregation of bacteria, even between different strains, is a topic that I never lectured about in my 50 years of teaching at the university level. Yet, as I researched this topic, it became apparent to me that most bacteria in nature exist in an aggregated state and this could promote quorum sensing among the aggregated cells and thus make the aggregate more likely to attach to a membrane surface.

Knowing that a membrane biofilm may begin as a protobiofilm from precursors has allowed myself to investigate its inhibition in a different light. While this paper had focused on just TEP as the important biofouling agent, it has allowed me to see a bigger picture of membrane biofouling in a world of many different aggregated bacteria and EPS matrices, not just TEP.

About the nominator Harvey Winters is Professor Emeritus at Fairleigh Dickinson University (FDU), Teaneck, New Jersey, USA. He received his Ph.D. degree from Columbia University in New York City. Initially, he studied biofilm formation on heat exchanger surfaces; but once he joined the faculty at FDU, he focused his teaching and research on RO membrane biofilm formation. Professor Winters has published extensively on the mechanism of membrane biofouling, particularly when he was a visiting scientist at Nanyang Technological University (NTU) in Singapore and King Abdullah University of Science & Technology (KAUST) in Saudi Arabia.

The Invention of the modern RO membrane by Loeb, S., and Surirajan, S. 1964. US Patent 3,133,132. And the thermodynamics of the process by Spiegler KS, Kedem O. Thermodynamics of hyperfiltration (reverse osmosis): criteria for efficient membranes. Desalination. 1966;1:311–326.

Nominated by: Raphael, PhD, PE Department of Chemical Engineering Technion, Israel Institute of Technology cesemiat@technion.ac.ii

My first introduction to desalination was during my PhD research at the Technion., I worked on multi effect distillation at that time and found the field fascinating. Upon returning from industry to the Technion I decided to continue with this exciting field. Two main techniques competed on the small desalination market at that time. This was a healthy competition that caused cost reduction and hence increased the desalination market. I was impressed mainly by two articles. The first is the patent of Loeb and Surirajan that was based on the reduction of mass transfer resistance to water passage through a tinner membrane and in fact invented the modern RO membranes. Sydney Loeb immigrated to Israel and built his second desalination plant in the center on the Negev Desert, supplying desalinated brackish water. Professors Spiegler and Kedem, provided us with the first explanation and theory on the thermodynamics of water passage through the membrane. At that time, an important question was if the polymeric thin layers will be able to compete with the strong, massive structure of the evaporation techniques. Based on the opportunity of the RO technique, Professor Hasson and I decided to promote the Desalination subject in our country, to help the industry involved and convince the decision-makers. We established the Israel Desalination Society with our partners at the academy and industry. We had the honor to have Professor Kedem and Dr. Loeb on our board and as keynote lecturers and award whiners in our meetings. This effort was a big success. Currently, about 80% of the urban water supplied by desalination. With all the experience gained, water cost went down significantly.

As researchers we try to continue and improve the processes. Especially the issues of fouling prevention, improved wastewater treatment, the energy consumed and the environmental issues of desalination and even develop a simple technique for removing calcium from seawater what improve the ability of cost reduction in evaporation processes.

About the nominator Raphael (Raf) Semiat is a Professor EM at Technion IIT, Israel, serving as the president of the Israel Desalination Society. Previously, co-editor at DESALINATION. Having industrial experience in process development, he published many articles on different issues in desalination and water purification, related to membrane processes, evaporation techniques, fouling issues, analysis of desalination technologies and reviews on energy consumption and related environmental issues.

by K.L. Lee et al. K.L.Lee, R.W.Baker, H.K.Lonsdale "Membranes for power generation by pressure-retarded osmosis" Journal of Membrane Science, Volume 8, Issue 2, 1981, Pages 141-171. https://doi.org/10.1016/S03767388(00)82088-8

Nominated by: Menachem Elimelech Department of Chemical and Environmental Engineering Yale University menachem.elimelech@yale.edu https://elimelechlab.yale.edu/menachem-elimelech

MLee et al. presented an excellent overview, derivation, and experimental results for the behavior of water flux through osmosis membranes, clearly delineating the regimes of reverse osmosis (RO), pressure retarded osmosis (PRO), and forward osmosis (FO). Although the title of the paper indicates only PRO, the authors described in detail the entire three regimes of RO, PRO, and FO. The derivation of the equations is given in detail and in a simple and clear way that is understandable at the undergraduate level.

Notably, one of the authors, Harry Lonsdale, was one of the pioneers in the development of the RO membrane technology. He had numerous other pioneering papers on the chemistry and properties in RO membranes. Lonsdale was also the founder and first editor of the Journal of Membrane Science and later had a political career in the State of Oregon. Another author of this classic paper, Richard Baker, is the founder of Membrane Technology and Research, Inc. (MTR) and the author of the authoritative book “Membrane Technology and Applications.” When we started our research on FO at Yale in 2002, we were puzzled by the very low water fluxes obtained in the lab with commercial RO membranes. Luckily, the graduate students in my lab immediately came across this paper which clearly described the phenomenon of internal concentration polarization and showed the complete derivation of the equations for predicting the water flux. We also referred to this paper when we carried out research on PRO as the paper clearly explained the relationship between hydraulic pressure, water flux, and maximum power density in PRO.

I have used this paper in my undergraduate course on environmental transport processes to illustrate the establishment of an internal concentration polarization profile within the membrane support layer under the action of convective and diffusive mass transfer. I have also referred to this paper in my graduate-level course on environmental physicochemical processes to illustrate internal concentration polarization as a performance-limiting phenomenon in membrane processes.

The paper has been very useful to researchers in the fields of FO and PRO as indicated by its large number of citations. The paper is unique because it combines detailed and lucid derivations of the performance equations of PRO and FO with experimental results and discussion of underlying mechanisms. With the deluge of incremental papers on this subject in the past decade, it is refreshing to refer to this classic paper and appreciate its contribution to the field of membrane science and desalination.

About the nominator Menachem Elimelech is the Roberto Goizueta Professor at the Department of Chemical and Environmental Engineering at Yale University. His research focuses on membrane-based technologies at the water-energy nexus. Professor Elimelech was the recipient of numerous awards in recognition of his research contributions, including the 2005 Clarke Prize, election to the US National Academy of Engineering in 2006, the Eni Prize for ‘Protection of the Environment’ in 2015, and election to the Chinese Academy of Engineering in 2017.

by Sidney Loeb, Desalination, vol. 1 (1966) pp. 35–49

Nominated by: Miriam Balaban Desalination, Editor-in-Chief Emeritus (1966–2009) Desalination and Water Treatment, Editor-in-Chief (2009 to date) Secretary General EDS, Research Associate MIT balabanmiriam@gmail.com, balaban@mit.edu

One of the first papers I published in Volume 1 of Desalination was this paper by Sidney Loeb. His greatest pride was the plant at Coalinga (Coaling Station A), CA since it did not only describe the technology but proved that fresh water could be produced from a plant using synthetic RO tubular membranes from a cellulose acetate polymer membrane. He described techniques for fabricating a composite tubular assembly.

For the rest of his life at many of the conferences which he attended, Sid displayed the plaque which hung in the plant because it was there that he not only proved that the technology could work, but most meaningful since it could open a way in which RO could provide water to a thirsty world.

Sid Loeb noted that anisotropy is the seminal feature to the success of RO desalination, and has been a major contributor to the general surge of interest in, and applications of membrane separation processes. The first test with an anisotropic membrane (not known at the time) was close to being a success. The second test (from the same membrane sheet) was a dismal failure with subsequent tests being equally good or very bad in random fashion, as if flipping a coin. He finally speculated that one side of the membrane was different from the other and that was it. The side facing the air during casting on a glass plate had to be in contact with the saline solution during service.

He went on to develop reverse osmosis research and propose new ideas such as pressure retarded osmosis (PRO) and reverse electrodialysis.

He published many other papers in Desalination and in other journals, but this pioneering paper was most significant for him. Not long before he passed away, Sid left me all his papers from which I published “The Collected Papers of Sidney Loeb 1917–2008” now available online (www.desline.com, www. deswater.com). Having reviewed and published over 20,000 papers over half a century, it is difficult to choose favorites. However, I will mention authors of some of the first significant papers: R.L. Riley, M.N. Ali El-Saie, K.S. Spiegler and O. Kedem, U. Merten, H. Lonsdale, D. Othmer and others.

Comments I was pleased to see that Prof. John Lienhard chose Prof. Robert Silver and Prof. Yehia M. El Sayed, pioneers in the field of desalination. Both were very significant to me.

I first met Prof. Silver at the memorable First International conference on Fresh Water from the Sea in Athens. He invited me to dinner and made sure that I knew that King James VI of Scotland became

Left to right: R.S. Silver, M. Balaban, K. Kraus, K. Fischbeck. Above: Zeus

King James I of England. This was the beginning of a life long friendship during which we discussed not only MSF and served on Dechema Committee on Fresh Water from the Sea, but also literature. He gave me the books he authored: The Bruce, Robert I King of Scots, a play and Poems: Conflict and Contexta and even music which he composed and sang to me over the phone, in his last days in the isle of Mull, Scotland.

I also enjoyed collaboration with Prof. Yehia M. El Sayed and Prof. K.S. Spiegler whose book I published.

Desalination Primer Introductory book for students and newcomers to desalination.

I wish to note that I greatly enjoyed collaboration with Prof. John Lienhard from his entrance into the field of desalination and swiftly becoming a major player in the field. He sustains the significant contributions of MIT from Prof. Ronald Probstein, Bill Katz, Frank Leitz and others.

About the nominator Miriam BALABAN is a graduate in chemistry from the University of Pennsylvania in Philadelphia, USA. She is the founder of Desalination, the international journal for desalting and purification of water, and was its Editor-in- Chief from 1966 to 2009. In 2009 she launched the monthly journal Desalination and Water Treatment to accommodate the growing flood of papers in the field and enable prompt publication. She is editor and publisher of the Desalination Directory, the international online database in desalination water reuse. She is the Secretary General of the European Desalination Society with its headquarters in Italy, where she organizes courses, conferences, and workshops in desalination. She is associated with the desalination program – Center for Clean Water and Energy – in the Department of Mechanical Engineering of the Massachusetts Institute of Technology (MIT). She has received the Lifetime Achievement Award from the International Desalination Association and Star of Honor from the President of Italy. She has been adviser to the African Academy of Science in establishing the journal “Discover” and establishing the African Association of Science Editors.

We hope that you found the above interesting or at least entertaining. How can we improve on the concept? Should we continue along this line and publish a second such column for the next issue? Most important, if you like the idea, who would you like us to tap next for their favorite papers? Please contact us directly with your thoughts.

Jantje Johnson,

IDA Publications Committee, Jantje@orangeboatsupport.com Jim Birkett,

at large, westneck@aol.com