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PubMed | Dow Water and Process Solutions, Curtin University Australia, King Abdullah University of Science and Technology, Eawag - Swiss Federal Institute of Aquatic Science and Technology and University of the Pacific of Ecuador
Type: | Journal: Water research | Year: 2016

Reducing membrane fouling caused by seawater algal bloom is a challenge for regions of the world where most of their freshwater is produced by seawater desalination. This study aims to compare ultrafiltration (UF) fouling potential of three ubiquitous marine algal species cultures (i.e., Skeletonema costatum-SKC, Tetraselmis sp.-TET, and Hymenomonas sp.-HYM) sampled at different phases of growth. Results showed that flux reduction and irreversible fouling were more severe during the decline phase as compared to the exponential phase, for all species. SKC and TET were responsible for substantial irreversible fouling but their impact was significantly lower than HYM. The development of a transparent gel layer surrounding the cell during the HYM growth and accumulating in water is certainly responsible for the more severe observed fouling. Chemical backwash with a standard chlorine solution did not recover any membrane permeability. For TET and HYM, the Hydraulically Irreversible Fouling Index (HIFI) was correlated to their biopolymer content but this correlation is specific for each species. Solution pre-filtration through a 1.2 m membrane proved that cells and particulate algal organic matter (p-AOM) considerably contribute to fouling, especially for HYM for which the HIFI was reduced by a factor of 82.3.

Costanzo J.A.,University of Virginia | Ober C.A.,University of Virginia | Black R.,Dow Water and Process Solutions | Carta G.,University of Virginia | Fernandez E.J.,University of Virginia
Biomaterials | Year: 2010

Acute liver failure arises when potentially toxic metabolites accumulate in the bloodstream because of a breakdown in liver function. New extracorporeal systems combining membrane and adsorbent technologies are being developed to replace critical liver detoxification functions between diagnosis and transplantation. This study addresses the adsorption of representative plasma components on four different hydrophobic, polymeric adsorbents for possible use in an extracorporeal hemodialysis device. The adsorbents considered span a range of pore sizes and include both strongly hydrophobic divinylbenzene (DVB) matrices as well as a less hydrophobic acrylate matrix. Adsorption equilibrium and rate measurements were made for these matrices using human serum albumin (HSA), polyclonal human immunoglobulin G (IgG), and bilirubin (BR), as representative plasma components. Pore size was found to contribute significantly to selectivity. Results demonstrated that strongly hydrophobic materials with pore sizes that allow free access to protein-bound BR are most effective for BR removal whether they are initially clean or pre-saturated with HSA. © 2009 Elsevier Ltd. All rights reserved.

Majamaa K.,Dow Water and Process Solutions | Johnson J.E.,Dow Water and Process Solutions | Bertheas U.,Dow Microbial Control
Desalination and Water Treatment | Year: 2012

Exposure to water containing micro-organisms causes biofouling on reverse osmosis (RO) membranes as they adhere, multiply and produce extracellular polymeric substances (ESP) which form biofilm on the surface of the membrane. As micro-organisms are present in virtually every water system, biofouling is one the most commonly encountered fouling types in large and small scale RO installations treating surface, wasteor seawater. Biofouling control is significantly improved when multiple methods are combined in an integrated approach and prevention methods employed in the RO stage itself are applied. In this study the impact of new membrane chemistry, feed spacer thickness and the use of non-oxidative biocide upon to the rate of biofouling in RO systems was investigated using a pilot-scale experiment involving small membrane elements subject to a high-fouling feed and autopsy-based analysis of membrane foulant loading and composition. The results were as follows: (1) The benefit of using the newest development in the family of fouling resistant (FR) membranes, DOW FILMTEC™ BW30XFR, was validated with side-by-side operation where lower rate of flux loss was observed when compared to the current industry standard membrane, BW30. (2) Thicker feed spacers provided reduced pressure drop and reduced rate of pressure drop increase during episodes of fouling. Overall organic foulant loading and bacterial counts were found to be reduced on membrane used in combination with thicker spacers. (3) The clear benefit of DBNPA dosing was observed with both shock and continuous dosing regimes. The benefit was most visible in the evolution of Δp as the treated elements operated at significantly lower Δp. Autopsy based results verified significantly lower organic fouling loading on the biocide treated element. These results point to the value of the studied factors-membrane chemistry, feed spacer configuration, and biocide dosing-for use with high-fouling feeds. The suggested route is to combine the components for use as an integrated strategy to solve biofouling. Combining a FR membrane with a thick feed spacer is preferred whenever a high potential for biofouling is seen. The use of targeted biocides in the pretreatment section will further result in improved fouling prevention and ensure long-term trouble free operation, maximizing the membrane lifetime and minimizing the operational expenses of the treatment system. © 2012 Desalination Publications. All rights reserved.

Majamaa K.,Dow Water and Process Solutions | Warczok J.,Dow Water and Process Solutions | Lehtinen M.,Dow Water and Process Solutions
Water Science and Technology | Year: 2011

Nanofiltration (NF) is an attractive technology for potable and industrial water treatment because NF operates between ultrafiltration (UF) and reverse osmosis (RO) membranes. NF is designed to remove a high percentage of organic contaminants (humic acids, pesticides, color bodies) while passing a medium to high percentage of salt. Compared to UF membranes, the NF product water quality is significantly better; compared to comparable RO treatment systems NF systems require lower operating pressures. Due to these features, NF is increasingly used in a broad range of water treatment applications. The general applications include softening, as well as color, organics and micro-organism removal. DOW FILMTEC™ NF270-400 is one the most frequently used elements in water treatment and this paper presents examples of three recent NF270-400 installations in Europe. The first two plants, Eupen and Stembert, are located in Belgium and produce potable water from surface water. The third one is a Scandinavian plant which purifies groundwater for a brewery and soft drink production. The presented operation results prove NF to be a highly competitive technique for low cost water treatment. © IWA Publishing 2011.

Khan M.T.,King Abdullah University of Science and Technology | Busch M.,Dow Water and Process Solutions | Molina V.G.,Dow Water and Process Solutions | Emwas A.-H.,King Abdullah University of Science and Technology | And 2 more authors.
Water Research | Year: 2014

To study the effect of water quality and operating parameters on membrane fouling, a comparative analysis of wastewater (WW) and seawater (SW) fouled reverse osmosis (RO) membranes was conducted. Membranes were harvested from SWRO and WWRO pilot plants located in Vilaseca (East Spain), both using ultrafiltration as pretreatment. The SWRO unit was fed with Mediterranean seawater and the WWRO unit was operated using secondary effluent collected from the municipal wastewater treatment plant. Lead and terminal SWRO and WWRO modules were autopsied after five months and three months of operation, respectively. Ultrastructural, chemical, and microbiological analyses of the fouling layers were performed. Results showed that the WWRO train had mainly bio/organic fouling at the lead position element and inorganic fouling at terminal position element, whereas SWRO train had bio/organic fouling at both end position elements. In the case of WWRO membranes, Betaproteobacteria was the major colonizing species; while Ca, S, and P were the major present inorganic elements. The microbial population of SWRO membranes was mainly represented by Alpha and Gammaproteobacteria. Ca, Fe, and S were the main identified inorganic elements of the fouling layer of SWRO membranes. These results confirmed that the RO fouling layer composition is strongly impacted by the source water quality. © 2014 Elsevier Ltd.

Shu J.,Dow Water and Process Solutions | Johnson J.E.,Dow Water and Process Solutions
AWWA/AMTA 2014 Membrane Technology Conference and Exposition | Year: 2014

Controlled studies are needed which examine the anti-biofouling benefits of new membrane and module innovations. Such investigations are often very small in scale, or they may lack sufficient control over feed water properties, or fail to compare against a control group of membranes, or run outside the normal operating ranges of RO systems. To address these problems, a pilot-scale facility and test method were developed to carefully investigate biofouling of RO modules. To allow side-by-side comparisons, the test bench was designed with two banks of 2.5-inch diameter by 40-inch long membrane modules. The use of eight 40-inch modules in series ensured that the results were readily scaled to full-size RO systems. The banks of modules were operated at industry-typical values of flux and recovery, and were cleaned when the feed-side pressure drop reached limits commonly imposed upon 8-inch diameter modules in full-size systems. The banks were supplied a softened, filtered well water dosed with sodium acetate. This facilitated rapid bio-growth, so that three controlled fouling and cleaning cycles were executed over a period of eight weeks. Results are presented which demonstrate reproducibility between the banks of modules and repeatability in the rate of fouling. Measurement of the feed-side pressure drop across individual modules showed that fouling was limited to the first three modules in each bank. Estimation of the membrane permeance at each module position showed that the increase in system feed pressure was due primarily to increased pressure drop, rather than reduced permeability due to biofilm. Copyright © 2014 by the American Water Works Association.

Stevens D.M.,Dow Water and Process Solutions | Mickols B.,Dow Water and Process Solutions | V. Funk C.,Dow Water and Process Solutions
Journal of Membrane Science | Year: 2014

Reverse osmosis membranes based on partially disulfonated copolymers of biphenol and aryl sulfone (BPS) have been studied in an asymmetric architecture. In these films, BPS represents both the porous support and solute rejection layer of the membrane. A procedure was developed to fabricate these asymmetric films through phase inversion of BPS solutions. Recipe optimization and the inclusion of several post-treatment steps to densify the rejection layer and heal defects gave the largest improvements in salt passage and are described in detail. A strong dependence of the final salt passage on ionic strength and temperature of the annealing solution is demonstrated. Under 2000. ppm NaCl and 15.5. bar test conditions, membranes were developed with salt passage from 0.34% to 1.81% across a flux range of 2.5-20. lmh. This performance represents a step change in the capability of BPS membranes for reverse osmosis. To achieve competitiveness with commercial polyamide membranes, several challenges required for continued improvements and commercialization are discussed. © 2013.

Poppe G.,Dow Water and Process Solutions
Chemical Processing | Year: 2012

Some proactive steps that can maximize life and performance for water purification and reduce overall operating costs of the RO plant are discussed. It is essential to normalize the permeate flow, feed pressure and salt passage to a standard reference point. Before starting to clean, find out the cleaning pH and temperature limits set by the membrane manufacturer and make sure the cleaning chemicals are compatible with the membranes. Once cleaning chemicals have displaced water, recycle concentrate and permeate to the cleaning tank. After the soak, recirculate the cleaning solution at a high flow rate for 30-60 minutes to flush out foulants removed from the membrane surface. Flush out the cleaning solution using RO permeate or deionized water and during the flush, the minimum temperature should be 20°C.

Desai S.,Dow Water and Process Solutions | Klanecky D.A.,Dow Water and Process Solutions
Chemical Engineering Progress | Year: 2011

Engineers must understand the water-energy nexus in order to manage both efficiently and sustainably. All thermal cycle plants require large quantities of water for cooling and condensing. Where economically and environmentally feasible, electric companies prefer to use water from a lake or river or from a cooling pond, instead of a cooling tower. This type of cooling can eliminate the capital cost of building a cooling tower. Thermal cycle plants require water for cooling, but it does not have to be freshwater. A power generation facility located near the ocean has the option to use seawater. Such a site would not use cooling towers, and discharge water temperatures would have less of an environmental impact. Advances in chemical engineering can facilitate reductions in energy consumption for water processing in two important areas, water treatment and the treatment of contaminated water and wastewater for reuse. New approaches to reducing the energy footprint of water treatment systems involve capturing waste energy throughout the treatment process.

Funk C.V.,Dow Water and Process Solutions | Koreltz M.S.,Dow Water and Process Solutions | Billovits G.F.,Dow Chemical Company
Journal of Applied Polymer Science | Year: 2016

Nylon 11 and Nylon 12 are commercially important polymers due to their unique combination of mechanical strength, chemical resistance, and processability. Products have been prepared from these polymers via thermally induced phase separation (TIPS) for many years. Nevertheless, known diluents for Nylon 11 and 12 pose specific processing problems, and it would be desirable to find a diluent that allows low processing temperatures, has a high flash point, is inexpensive, and exhibits low toxicity. This work investigated a variety of alternative diluents not previously documented in the literature. A fundamental study was also performed to determine which factors are important in selecting a diluent for preparing Nylon liquid-liquid TIPS membranes. The information gathered in this study, including phase diagrams for all feasible systems investigated, will be important in shaping future formulation work for Nylon use in microporous membranes. © 2015 Wiley Periodicals, Inc.

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