PROFESSOR RAPHAEL SEMIAT
Personal Background
Date and place of birth: November 5, 1948; Haifa, Israel Marital status: Married + 3
Academic Degrees
1978 PhD Technion – ITT
1973 BSc (cum laude), Chemical Engineering, Technion – ITT
Professional Experience
1980 – 1983 Senior researcher: TAMI (IMI). Process development work
1983 – 1989 Head of Department: “Heat and Mass Transfer Processes”, TAMI (IMI), the Central Research and Development Laboratories of ICL - the Israel Chemicals Corporation. R&D projects performed to daughter companies of ICL (Dead Sea Works, Dead Sea Bromine, Bromine Compounds, Negev Phosphates, Rotem Fertilizers, Periclass, Fertilizers and Chemicals, Desalination Engineering).
1989 to present Faculty member, Technion – ITT
Current Academic Appointment
2003 Professor, Wolfson Faculty of Chemical Engineering, Technion Director of the Grand Water Research Institute
Research Interests
Heat and mass transfer phenomena in separation processes
Experimental hydrodynamics of industrial gas-liquid, liquid-liquid and solid-liquid systems
Application of electro-optical techniques in the study of two-phase flow systems Water technologies with emphasis on water desalination aspects
List of Recent Publications
1. Semiat, R., Hasson, D., Zelmanov, G. and Hemo,I., “Threshold scaling limits of RO concentrates flowing in a long waste disposal pipeline” Water Science & Technology 49,2 211–219 2004
2. Yang, Qingfeng; Ma, Zifeng; Hasson, David; Semiat, Raphael. “Destruction of anti-scalants in RO concentrates by electrochemical oxidation” Huagong Xuebao (Chinese Edition) (2004), 55(2), 339-340.
3. Sagiv, A. and Semiat, R. “Analysis of parameters affecting boron permeation through reverse osmosis membranes” Journal of Membrane Science (2004), 243(1-2), 79-87.
4. Ramon, G., Green, M., Semiat, R. and Dosoretz, C., “Low strength graywater characterization and treatment by direct membrane filtration” Desalination 170 (2004),241-250
5. Sagiv, A. and Semiat, R. “Backwash of RO spiral wound membranes”, Desalination, 179(2005)1-9
6. Greenberg, G., Hasson, D. and Semiat, R., “Limits of RO recovery imposed by calcium phosphate Precipitation”, Desalination 183 (2005) 273-288.
7. Lisitsin, D., Yang, Q., Hasson, D. and Semiat, R., “Inhibition of CaCO3 scaling on
RO membranes by trace amounts of zinc ions”, Desalination 183 (2005), 289-300
8. Ivnitsky H., I. Katz, D. Minz, E. Shimoni, Y. Chen, J. Tarchitzky, R. Semiat and C.G. Dosoretz, “Characterization of Membrane Biofouling in Nanofiltration Processes of Wastewater Treatment” Desalination 185 (2005),255-268.
9. Gimmelshtein (Modek) M. and R. Semiat, “Investigation of Flow Next to Membrane Walls” Journal of membrane Science (2005), 264(1-2), 137-150.
10. Lisitsin, D., Hasson, D. and Semiat, R. “Critical flux detection in a silica scaling RO system” Desalination 186, (2006) 311-318.
11. Singh, A., Nir, A. and Semiat, R., “Free-surface flow of concentrated suspensions” accepted to the Journal of Multi Phase Flow. International Journal of Multiphase Flow (2006), 32(7), 775-790.
12. Hasson, D. and Semiat, R. “Scale Control in Saline and Wastewater Desalination” Israel Journal of Chemistry (2006), 46(1), 97-104.
13. Yang Q., Lisitsin D., Hasson D. and Semiat, R. “Inhibition of CaCO3, scaling in reverse osmosis system by zinc ion” (vol. 14, pg 178, 2006) Chinese Journal of Chemical Engineering 14 (4): 554-554 AUG 2006
14. Geffen. N., Semiat, R., Eisen M., Balazs Y., Katz I. and Dosoretz, C. G., “Boron Removal from Water by Complexation to Polyol Compounds” Journal of membrane Science, (2006), 286(1-2), 45-51.
16. Hanan Ivnitsky, Ilan Katza, Dror Minz, Galit Volvovic, Eyal Shimoni, Elina Kesselman, Raphael Semiat and Carlos G. Dosoretz, “Bacterial community composition and structure of biofilms developing on nanofiltration membranes applied to wastewater treatment”, Water Research 41, 17, September (2007), 3924-3935.
17. Yang, Q., Lisitsin, D., Liu, Y., David, H., Semiat, R. ”Desupersaturation of RO concentrates by addition of coagulant and surfactant” Journal of Chemical Engineering of Japan 2007 40 (9), pp. 730-735
18. Yang, Q., Drak, A., Hasson, D., Semiat, R., “ RO module RTD analyses based on directly processing conductivity signals” Journal of Membrane Science, 306, 1-2, 2007, 355-364
19. Bach, A., Zelmanov, G. and Semiat, R. “Cold Catalytic Recovery of Loaded Activated Carbon Using Iron Oxide Nanoparticles, Water Research 42 (2008) 163 – 168
20. Zelmanov, G. and Semiat, R. “Iron (3)-OxideNanoparticles as Catalysts in Advanced Organic Aqueous Oxidation”, Water Research 42 (2008) 492 – 498.
21. Lisitsin, D., Hasson, D., Semiat,R., “The potential of CO2 stripping for pretreating brackish and wastewater desalination feeds” Desalination (2008), 222,50-58
22. Kabay, N., Sarp, S. Yuksel, M., Kitis, M., Koseoglu, H., Arar, O., Bryjak, M. and Semiat R.,”Removal of boron from SWRO permeate by boron selective ion exchange resins containing N-methyl glucamine groups” Desalination, (2008),223,49-56
23. Shannon, M. A. and Semiat, R., Guest Editors “Advancing Materials and Technologies for Water Purification” MRS Bulletin January 2008,: 33,1-4
24. Vainrot, N., Eisen, M. and Semiat, R. “Membranes in desalination and water treatment” in “Materials and Technologies for Water Purification” MRS Bulletin January 2008, 33,5-9.
25. Yang, Q.F., Drak, A., Hasson, D., Semiat, R. “Direct processing of RTD signals from conductivity data in spiral wound RO modules”, (2008) Journal of Chemical Engineering of Japan, 41 (1), pp. 1-5.
26. Yang, Q.F., Liu, Y., David, H., Semiat, R.” Scaling salt removal by addition of inorganic particles”, Journal of Chemical Engineering of Japan, (2008) 41 (1), pp. 6-12.
In print:
1. Zach-Maor A., Semiat R., Rahardianto A., Cohen Y., Wilson S., Gray S.R., “Diagnostic analysis of the technical feasibility of RO desalting of treated wastewater 230(2008)239-247
2. Hasson, D., Lumelsky L., Greenberg, G., Pinhas, Y. and Semiat, R., “Development of the Electrochemical Scale Removal Technique for Desalination Applications”, Desalination 230 (2008) 329-342.
3. Yuan, P.Q., Kong, N., and Semiat, R., “Electrostatic Potential on Anti-scalants Modified CaCO3 (104) Surface: A Molecular Simulation Study” Desalination 2xx
(2008) 000–000
4. Link N. and Semiat R. “Ink Drops Motion in Large Format Printers I. Drops Flow from DOD Printing Heads”. CEP
Abstracts
Critical flux detection in a silica scaling RO system
Lisitsin, D., Hasson, D. and Semiat, R.
Desalination 186, 311-318, 2006
Reverse osmosis desalination has achieved prominence as the most cost effective desalting technology. The objective of the present paper was to develop adequate tools for diagnosing malfunctioning of the generally adopted spiral wound module design. Efforts were undertaken to apply residence time distribution (RTD) techniques combined with concentration polarization (CP) determinations for characterizing the degree of uniformity of flow in spiral wound membrane passages and diagnosing flow mal-distribution defects.
Axial mixing intensities were evaluated from experimental RTD measurements on the basis of the Exponentially Modified Gaussian Model (EMG). The levels of the axial mixing intensities, characterized by the dispersion coefficient, indicated significant deviations from ideal plug flow. Theoretical analyses showed that the presence of axial dispersion can result in significant deviations from the module performance characteristics evaluated according to the usual assumption of ideal plug flow.
A striking concentration polarization result was that increase of the Reynolds number (Re) reduced the CP level as expected, but only up to a certain critical Re after which the CP level increased with Re. This result can be explained by the effect of Re on the dispersion level.
Free-surface flow of concentrated suspensions
Singh, A., Nir, A. and Semiat, R.
Accepted to the Journal of Multi Phase Flow. International Journal of Multiphase Flow
32(7), 775-790, 2006
Free surface flows of concentrated suspensions exhibit many interesting phenomena such as particle segregation and surface corrugation. In this work the flow structures associated with free surface has been studied experimentally. The free surface velocity for neutrally buoyant suspension of uniform spheres in a gravity driven inclined channel flow was determined by particle imaging velocimetry (PIV) technique. Experiments were carried out for concentrated suspensions with particle fractions φ ranging from 0.40 to 0.50. The measured velocities show blunted profile in the channel. The blunting of the velocity profile increases with the particle concentration. The rms velocity fluctuations measured at the free surface progressively increase with particle fraction φ and are linear in shear rate γ. The surface roughness were characterized by analyzing the power spectral density of the refracted light from the free surface. The characteristics observed are in support of the earlier findings of Loimer et al. (2002).
Scale control in saline and wastewater desalination
Hasson, D. and Semiat, R.
Israel Journal of Chemistry46(1), 97-104, 2006
Boron removal from water by complexation to polyol compounds
Geffen. N., Semiat, R., Eisen M., Balazs Y., Katz I. and Dosoretz, C. G.
Journal of Membrane Science286(1-2), 45-51, 2006
Boron is an important micronutrient for plants, animals and humans, although the range between deficiency and excess is narrow. The use of desalinated water and treated wastewater for irrigation may result in excess boron. In aqueous environments (i.e. neutral pH) boron is mainly present as boric acid, which is mostly undissociated and therefore only partially rejected by desalination membranes.
Boric acid/borate reacts with neutral polyolic compounds, generating anionic complexes. This work reports on the complexation of boron with mannitol integrated with membrane desalination. The separation of the complex was studied in a wide range of conditions by nanofiltration (NF), and partially by reverse osmosis (RO) membranes. NMR analysis and chemical equilibrium modeling system (Mineql+) were applied to provide a better understanding of experimentally observed rejection patterns.
The addition of mannitol in excess formed mainly a 2,2-di-borate ester and some monoborate esters as function of the pH, improving boron rejection by NF up to 90% at pH 9. Mineql+ calculations indicate that reactants concentration has a strong influence on the ionized boron species and therefore on the rejection of boron. Sea water-RO membranes having a much higher basal rejection for boric acid, rejected almost 97% mannitol-complexated boron at pH of 9.
Detection of fouling on RO modules by residence time distribution analyses
Hasson, D., Drak, A., Komlos, C., Yang, Q. and Semiat, R.
Desalination 204(1-3), 132-144, 2007
A simple and reliable technique for on line detection and diagnosis of scaling and fouling deposits could improve significantly operational control of RO plants. This paper presents results of an ongoing research project aiming to develop a novel method for online detection of membrane fouling by a residence time distribution (RTD) technique. The method is based on determination of flow dispersion intensities from online RTD signals that can be simply measured. The systems investigated in this paper are spiral wound membranes fouled with either Mg(OH)2 or CaCO3. Analyses of RTD data of fouled membranes show that an increasing
Bacterial community composition and structure of biofilms developing on nanofiltration membranes applied to wastewater treatment
Hanan Ivnitsky, Ilan Katza, Dror Minz, Galit Volvovic, Eyal Shimoni, Elina Kesselman, Raphael Semiat and Carlos G. Dosoretz
Water Research 41, 17, 3924-3935, September (2007)
The structure of biofilms and microbial communities developing on cross-flow nanofiltration (NF) membranes at different temperatures (20°C, 25°C, or 34°C) and operation lengths (8 h-24 d) were studied. Feedwater comprised tertiary quality wastewater effluent or synthetic media mimicking effluents of intermediate quality. After each run the membranes were autopsied for bacterial enumeration, bacterial community composition and microscopy visualization (SEM, CLSM and AFM/NSOM). Community composition was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCRDGGE) coupled with sequence analysis of 16S rRNA gene fragments from dominant bands.
Deposition of polysaccharides and initial bacterial colonization were observed within 8 hours, whereas developed biofilms markedly affecting membrane permeability were evident from day 2-3 onwards. Regardless of applied conditions, the heterotrophic plate counts in the biofilm were 2- 3-4×106 CFU/cm2 and the thickness of biofouling layer was 20-30 µm. From a total of 22 sequences obtained from 14 independent experiments most species identified were Gram-negative (19 of 22 sequences). Proteobacteria were found to be a prevalent group in all cases (16 of 22 sequences) and among it, the β-subclass was the most predominant (8 sequences) followed by the γ-subclass (5 sequences). Pseudomonas/Burkholderia, Ralstonia, Bacteroidetes and Sphingomonas, were the dominant groups found in most cases. Even though the microbial population might be important with respect to biofouling patterns, membrane permeability decline seems to be more substantially influenced by the formation and accumulation of exopolymeric substances (EPS).
Desupersaturation of RO concentrates by addition of coagulant and surfactant
Yang, Q., Lisitsin, D., Liu, Y., David, H., Semiat, R.
Journal of Chemical Engineering of Japan 40 (9), pp. 730-735, 2007
One way for the reuse of reverse osmosis (RO) concentrates and thus increasing the water recovery is to recycle part of the brine concentrate to the feed, after precipitating the scaling salts such as CaSO4/CaCO3 held in solution by antiscalants. However, antiscalants impart considerable
stability to the super-saturated solution. In the present study, desupersaturation of RO CaSO4
RO module RTD analyses based on directly processing conductivity signals
Yang, Q., Drak, A., Hasson, D., Semiat, R.
Journal of Membrane Science 306, 1-2, 355-364,2007
Residence time distribution (RTD) techniques can be used to diagnose the flow characteristics in spiral wound reverse osmosis (RO) modules. However, the methods of processing tracer response conductivity signals and mathematically modeling of RTD curves often involve complicated steps including conductivity-concentration transformation, baseline selection and the use of exit age distribution function of Et, or dimensionless exit age distribution function of Eθ. In this paper, a simple and direct method for processing RTD signals from conductivity data was developed for spiral wound membrane RO system. Two models were tested: axial dispersion (AD) model and exponentially modified Gaussian (EMG) model. The results show that the present method provides a simple, fast and accurate RTD data reduction. The levels of the axial mixing intensities, characterized by the dispersion number D/uL, indicated significant deviations from ideal plug flow in both the laboratory and the industrial size modules. In both the modules, the dispersion coefficient D increased roughly linearly with the Reynolds number. Membrane fouling and
worn-out led to an increase in D. Moreover, the values of mean residence time over(t, ̄) and D/uL
obtained from the EMG model were more stable against the change of the curve tail length, especially for the parameter D/uL. Furthermore, RTD analysis also indicated that the membrane wearing-out could lead to dead zones. © 2007 Elsevier B.V. All rights reserved.
Membranes in desalination and water treatment
Vainrot, Nataly; Eisen, Moris S.; Semiat, Raphael
MRS Bulletin 33(1), 16-20, 2008
