Effect of membrane character and solution chemistry on microfiltration performance

To help understand and predict the role of natural organic matter (NOM) in the fouling of low-pressure membranes, experiments were carried out with an apparatus that incorporates automatic backwashing and long filtration runs. Three hollow fibre membranes of varying character were included in the study, and the filtration of two different surface waters was compared. The hydrophilic membrane had greater flux recovery after backwashing than the hydrophobic membranes, but the efficiency of backwashing decreased at extended filtration times. NOM concentration of these waters (7.9 and 9.1 mg/L) had little effect on the flux of the membranes at extended filtration times, as backwashing of the membrane restored the flux to similar values regardless of the NOM concentration. The solution pH also had little effect at extended filtration times. The backwashing efficiency of the hydrophilic membrane was dramatically different for the two waters, and the presence of colloid NOM alone could not explain these differences. It is proposed that colloidal NOM forms a filter cake on the surface of the membranes and that small molecular weight organics that have an adsorption peak at 220 nm but not 254 nm were responsible for “gluing” the colloids to the membrane surface. Alum coagulation improved membrane performance in all instances, and this was suggested to be because coagulation reduced the concentration of “glue” that holds the organic colloids to the membrane surface

Fouling mechanisms in constant flux crossflow ultrafiltration

Four fouling models due to Hermia (complete pore blocking, intermediate pore blocking, cake filtration and standard pore blocking), have long been used to describe membrane filtration and fouling in constant transmembrane pressure (ΔP) operation of membranes. A few studies apply these models to constant flux dead-end filtration systems. However, these models have not been reported for constant flux crossflow filtration, despite the frequent use of this mode of membrane operation in practical applications. We report derivation of these models for constant flux crossflow filtration. Of the four models, complete pore blocking and standard pore blocking were deemed inapplicable due to contradicting assumptions and relevance, respectively. Constant flux crossflow fouling experiments of dilute latex bead suspensions and soybean oil emulsions were conducted on commercial poly (ether sulfone) flat sheet ultrafiltration membranes to explore the models’ abilities to describe such data. A model combining intermediate pore blocking and cake filtration appeared to give the best agreement with the experimental data. Below the threshold flux, both the intermediate pore blocking model and the combined model fit the data well. As permeate flux approached and passed the threshold flux, the combined model was required for accurate fits. Based on this observation, a physical interpretation of the threshold flux is proposed: the threshold flux is the flux below which cake buildup is negligible and above which cake filtration becomes the dominant fouling mechanism

Slow colloidal aggregation and membrane fouling

We observed that the concept of critical flux, although established on physical bases, does not describe all typical fouling situations found in membrane filtration. We especially focus on the slow flux decline that is observed in many industrial membrane applications, and that has found several types of explanations that we briefly discuss. In order to get a better understanding of this situation, we have considered the orders of magnitude of the slow aggregation kinetics that are expected to happen within a boundary layer, on an ultrafiltration or microfiltration membrane in operation. The results help to understand that whereas the critical flux is limiting cross-flow filtration of stable colloids, it should be combined to kinetics aspects of slow aggregation in cases of colloids of intermediate stability (metastable). We discuss some consequences on the design and operation of processes using membrane filtration

ENMat international projects: FP7 NMP coordination action: 2BFUNTEX

Boosting collaboration between research centres and industry to enhance rapid industrial uptake of innovative functional textile structures and textile-related materials in a mondial market 2BFUNTEX will exploit the untapped potential in functional textile structures and textile related materials. It will bring together all innovation actors in the field fostering a multidisciplinary approach between universities, research institutes, SMEs and sector associations. The 2BFUNTEX team will identify technological gaps and eliminate barriers resulting in a faster industrial uptake of added value functional materials with new functionalities and improved performance and resulting in creation of new business worldwide. Technological needs will be mapped, new joint international research disciplines will be identified and multidisciplinary lab teams will be created. International cooperation will be favoured to exploit the worldwide market expansion potential. Industry will be involved at all stages of the process. The inventory will enlarge the team of important textile universities and renowned materials research centres and will identify new collaborations. Synergy will be reinforced and created which will enable to identify and develop new functional materials. Training materials regarding functional materials for research and industrial purposes will be developed and implemented to allow a common language regarding functional textile structures and text ile related materials, and will increase the number of well-trained people in this field. Further, the 2BFUNTEX partners will organise and participate in conferences, workshops and brokerage events. Along with a website with an extensive database comprising all information gained throughout the project, collaboration will be boosted and rapid industrial uptake catalysed and enhanced. The project duration will be 4 years and the consortium includes 26 partners from 16 countries. Start date : 01/01/2012 More information: Ir. Els Van der Burght Department of Textiles/Ghent University [email protected] [email protected] URL: http://www.2bfuntex.e

Description of the biofouling phenomena affecting membranes by the boundary flux concept

Membrane fouling, showing up with a significant reduction of process productivity and membrane lifetime, is one of the main issues in membrane technologies and has been successfully described by the boundary flux concept. Although the concept was applied for both organic and inorganic fouling, biofouling enjoys partial treatises in literature. In this work, a model extending the boundary flux concept to biofouling issues was developed. A population dynamics-based model considering the development of a fouling layer originated by attached growing biomass on the surface of the membrane using nutrients and substrates available in the processed feed has been developed. The manuscript highlights the critical aspects of the developed model and the possible connection points between it and the boundary flux concept

ENMat international projects: FP7 NMP large collaborative project: 3D-LightTrans

Large scale manufacturing technology for high-performance lightweight 3D multifunctional composites The goal of the 3D-LightTrans project is to provide groundbreaking, highly flexible, efficient and adaptable low-cost technologies for the manufacturing of integral large scale 3D textile reinforced plastic composites, including innovative approaches for the individual processes and its integration in complete manufacturing chains, which will enable to shift them from its current position in cost intensive, small series niche markets, to broadly extended mass product applications, not only in transportation, but also in other key sectors, like health and leisure. To fulfil this goal, the 3DLightTrans manufacturing chains will be based on multimaterial semifinished fabrics, processed to deep draped prefixed multilayered and multifunctional 3D -textile preforms, which will be processed into composites by a thermoforming process. By integrating these new, innovative process steps with full automation in -nowadays mostly manually performed- complex handling operations, it will be possible to obtain a fully automated and highly adaptable manufacturing chain to achieve integral large scale 3D composites. 3D-LightTrans will open the way to a totally new concept for the design, manufacturing and application of composites for low-cost mass products in a wide range of sectors. The Consortium brings together multidisciplinary research teams involving European leading companies, including industrial stakeholders from machine tools and machine automation and several OEM active in the field of processing of flexible materials and composite manufacturing, as well as from the application sector, and extensive expertise from well known research specialists in the area of materials, production research and technical textiles in particular. Start date : 01/04/2011 Project duration : 4 years More information: Dr. Erich Kny Austrian Institute of Technology, [email protected] URL: http://www.3d-lighttrans.com

Sequential biological and photocatalysis based treatments for shipboard slop purification: A pilot plant investigation

This study investigated the treatment of a shipboard slop containing commercial gasoline in a pilot plant scale consisting of a membrane biological reactor (MBR) and photocatalytic reactor (PCR) acting in series. The MBR contributed for approximately 70% to the overall slop purification. More precisely, the biological process was able to remove approximately 40%, on average, of the organic pollution in the slop. Nevertheless, the membrane was capable to retain a large amount of organic molecules within the system, amounting for a further 30% of the influent total organic content removal. However, this affected the membrane fouling, thus resulting in the increase of the pore blocking mechanism that accounted for approximately 20% to the total resistance to filtration (2.85∙10 13 m −1 ), even if a significant restoration of the original membrane permeability was obtained after chemical cleanings. On the other hand, the biological treatment produced a clear solution for the photocatalytic system, thereby optimizing the light penetration and generation of highly oxidizing active oxygen species that enabled the degradation of bio-recalcitrant compounds. Indeed, low total organic carbon (TOC) values (<10 mg L −1 ) were achieved in the output of the photocatalytic reactor by means of only 60 Einstein (E) of cumulative impinging energy after the addition of K 2 S 2 O 8 . Overall, coupling the two processes enabled very high TOC removal (ca. 95%)

Ultrasound enhancement of microfiltration performance for natural organic matter removal

Sonication of water at 1500 W power prior to microfiltration showed that short sonication times (60 s) gave a reduced flux decline. It is suggested that a less potent, smaller molecular form of the natural organic matter (NOM) was produced by sonication. Longer sonication times diminished this beneficial effect. This may be due to the formation of aggregates or compounds that are more readily adsorbed on the membrane. Where the sonication was preceded by an alum treatment, the flux loss showed a regular decrease with longer sonication times. It is suggested that the effects of sonication on the alum flocs and on the flocs; NOM interactions may play a critical role in regulating the flux. Where sand was present on sonication at 800 and 1400 W, the cavitational energy was focussed on adsorbed organic material, resulting in more efficient destruction and the formation of compounds that counteracted the flux enhancement