Showing papers on "Fouling published in 2002"
TL;DR: An integrated approach is suggested which includes the analysis of the fouling situation, a selection of suitable components from the anti-fouling menu and an effective and representative monitoring of biofilm development.
Abstract: Biofouling is referred to as the unwanted deposition and growth of biofilms. This phenomenon can occur in an extremely wide range of situations, from the colonisation of medical devices to the production of ultra-pure, drinking and process water and the fouling of ship hulls, pipelines and reservoirs. Although biofouling occurs in such different areas, it has a common cause, which is the biofilm. Biofilms are the most successful form of life on Earth and tolerate high amounts of biocides. For a sustainable anti-fouling strategy, an integrated approach is suggested which includes the analysis of the fouling situation, a selection of suitable components from the anti-fouling menu and an effective and representative monitoring of biofilm development.
833 citations
TL;DR: Establishing a general model to describe membrane fouling in such a process is made extremely difficult by the inherent heterogeneity of the biomass matrix, which is highly heterogeneous and includes living microorganisms.
Abstract: Membrane bioreactors (MBRs), in which membranes are applied to biological wastewater treatment for biomass separation, provide many advantages over conventional treatment. However, membrane fouling in MBRs restricts their widespread application because it reduces productivity and increases maintenance and operating costs. Recently much research and development has taken place to investigate, model, and control membrane fouling processes. However, unified and well-structured theories on membrane fouling are not currently available because of the complexity of the biomass matrix, which is highly heterogeneous and includes living microorganisms. Membrane fouling in MBR systems can be reversible (i.e., removable by physical washing) or irreversible (removable by chemical cleaning only), and can take place on the membrane surface or into the membrane pores. Although establishing a general model to describe membrane fouling in such a process is made extremely difficult by the inherent heterogeneity of the syste...
714 citations
TL;DR: Although other studies have identified DOM as a major foulant during filtration of natural waters, this work shows that a small fraction of DOM may be responsible for fouling, and adsorption was demonstrated to be an important mechanism for fouled by colloids.
Abstract: Membrane filtration (microfiltration and ultrafiltration) has become an accepted process for drinking water treatment, but membrane fouling remains a significant problem. The objective of this study was to systematically investigate the mechanisms and components in natural waters that contribute to fouling. Natural waters from five sources were filtered in a benchtop filtration system. A sequential filtration process was used in most experiments. The first filtration steps removed specific components from the water, and the latter filtration steps investigated membrane fouling by the remaining components. Particulate matter (larger than 0.45 microm) was relatively unimportant in fouling as compared to dissolved matter. Very small colloids, ranging from about 3-20 nm in diameter, appeared to be important membrane foulants based on this experimental protocol. The colloidal foulants included both inorganic and organic matter, but the greatest fraction of material was organic. When the colloidal fraction of material was removed, the remaining dissolved organic matter (DOM), which was smaller than about 3 nm and included about 85-90% of the total DOM, caused very little fouling. Thus, although other studies have identified DOM as a major foulant during filtration of natural waters, this work shows that a small fraction of DOM may be responsible for fouling. Adsorption was demonstrated to be an important mechanism for fouling by colloids.
503 citations
TL;DR: In this article, the development of fouling in a cross-flow microfilter coupled to an anaerobic bioreactor has been studied, and a characteristic two-stage transmembrane pressure (TMP) profile was observed with an initially extended period of slow TMP rise followed by a sudden transition to a rapid TMP increase.
461 citations
TL;DR: In this article, the role of hydrodynamics (initial permeate flux and crossflow rate) and divalent cations (calcium) in natural organic matter (NOM) fouling of nanofiltration (NF) membranes is reported.
400 citations
TL;DR: In this article, the authors determined the impact of various operating factors on membrane fouling in activated sludge membrane bioreactor (MBR) process, typically used for water reclamation.
297 citations
TL;DR: In this paper, a laboratory-scale crossflow membrane filtration apparatus was designed to investigate the relative influence of filter geometry and shear rate on colloidal fouling of reverse osmosis (RO) and nanofiltration (NF) membranes.
Abstract: A laboratory-scale crossflow membrane filtration apparatus was designed to investigate the relative influence of filter geometry and shear rate on colloidal fouling of reverse osmosis (RO) and nanofiltration (NF) membranes. An expression that allows clarification of the mechanisms of flux decline due to colloidal fouling in RO and NF separations was derived by combining the solution-diffusion model, film-theory, and a modified cake filtration model. With this new fouling model, the interplay between the salt concentration polarization layer and a growing colloid deposit layer may be quantified. The hydraulic pressure drop across a colloid deposit layer was shown to be negligible compared to cake-enhanced osmotic pressure. The difference in flux decline observed in filters with different channel heights resulted from different cake layer thickness, and thus, different cake-enhanced osmotic pressure. A moderate reduction in the initial concentration polarization and cake-enhanced osmotic pressure was obtain...
291 citations
TL;DR: In this paper, both the NaCl solution and real seawater are used as the feed of MD processes to investigate the differences in permeate flux, product water quality and membrane fouling.
235 citations
TL;DR: In this article, the authors developed a fundamental understanding of the underlying mechanisms governing humic acid fouling during microfiltration using a combined pore blockage-cake filtration model.
226 citations
TL;DR: In this paper, the performance of an integrated activated sludge bioreactor-membrane microfiltration system was investigated, and the results reveal that the smaller particles played a more important role in membrane fouling.
214 citations
TL;DR: In this paper, a suitable reference membrane for the modified fouling index (MFI0.45), based on cake filtration, was investigated using polysulphone (PS) and polyacrylonitrile (PAN) UF membranes of 1-100kDa molecular-weight cut-off (MWCO) in tap water experiments.
TL;DR: In this article, an in-line coagulation (without settling)/UF process has been studied to improve membrane performance and water quality for surface water treatment, where the extent of dissolved organic matter removal is controlled by the coagulations step.
TL;DR: In this article, the authors evaluated the cleaning efficiency and effects of several cleaning agents on NF255 nanofiltration membrane and showed that the choice of chemical cleaning agent is critical to cleaning efficiency, both technically and economically.
TL;DR: In this paper, an ultrasonic technique was successfully applied to remove fouling and recover the permeate flux of flat sheet microfiltration (MF) membranes, and three kinds of cleaning methods were used, namely, forward flushing, ultrasonic cleaning and ultrasound with forwardflushing, and their cleaning efficiencies were compared.
TL;DR: In this paper, the effect of adsorption on membrane fouling during filtration of a membrane bioreactor (MBR) mixed liquor suspension was quantified using β-lactoglobulin solutions.
TL;DR: In this article, the most common causes of microfiltration membrane fouling are summarized and reviewed, the range of methods covered include feed pre-treatment, choice of membrane material, flow manipulation, the use of high shear, gas sparging and additional force fields.
TL;DR: In this article, the conditions of membrane surface gypsum scale formation during nanofiltration (NF) of agricultural drainage water were investigated, and a small plate-and-frame cross-flow membrane re-circulation unit was used to measure the effect of increasing recovery on the onset of scaling.
TL;DR: In this paper, a colourimetric staining technique was developed to determine the nature of organic foulants adsorbed onto the membranes and the anti-fouling potential of noncovalently attached coating materials was investigated as a possible membrane pretreatment technique.
TL;DR: In this article, the effect of pulsed electric fields on membrane fouling in electrodialysis was studied with NaCl solution containing humate and the optimum frequency was found to be 100 Hz in terms of conductivity and cell resistance changes.
TL;DR: In this paper, the Boltac Coagulation and Flocculation simulator was used to evaluate the effectiveness of chemical pretreatment for removal of silica and other species such as magnesium, calcium, iron and manganese which affect silica fouling.
TL;DR: A new mathematical model is developed to describe the change in transmembrane pressure during constant flux microfiltration, assumed to occur first by pore blockage, with a cake then forming over the blocked areas of the membrane.
TL;DR: In this paper, charged and non-charged hydrophilic polymers were grafted as a flexible layer onto a polypropylene hollow fibre to alter the surface properties and the electrostatic interactions between the feed components and the membrane surface.
TL;DR: In this article, the authors presented a correlation analysis of the data set obtained by Knudsen et al. for threshold fouling experiments performed in a pilot plant, which represented an attempt to model measured physical parameters that actually resulted in no observable fouling.
TL;DR: In this article, the cleaning of an ultrafiltration polyethersulfone (PES) membrane fouled by skimmed milk was studied by ATR-FTIR showing the functional groups of fouling species and EDX coupled with SEM measuring the atomic composition.
TL;DR: In this paper, the fouling characteristics of anion exchange membranes were investigated according to their electric resistances, hydrophobicities, exchange capacities and zeta potentials, and the results showed that AMX had the lowest fouling potential while ACM the highest.
TL;DR: The findings suggest that the broad antifouling properties of the crude extract of L. obtusa inhibit the settlement of fouling as well as hinder the development of settled fouling species, thereby reducing the richness of species.
Abstract: Antifouling activity is one poorly investigated property of seaweed natural products. To determine, in the field, whether seaweeds contain chemicals able to influence the settlement of fouling organisms, crude organic extracts from Stypopodium zonale, Dictyota menstrualis (Phaeophyceae) and Laurencia obtusa (Rhodophyceae) were incorporated at natural volumetric concentrations, into hard stable gels that served as substrata for fouling in the experiments. Fouling organisms settled at a significantly higher rate on plates treated with S. zonale extracts than on control gels, while settlement was strongly inhibited on gels containing L. obtusa extracts. Fouling on gels treated with the D. menstrualis extract was not significantly different from the fouling found on control gels. The findings suggest that the broad antifouling properties of the crude extract of L. obtusa inhibit the settlement of fouling as well as hinder the development of settled fouling species, thereby reducing the richness of species. Th...
TL;DR: In this paper, three feed pretreatments for a spiral wound reverse osmosis (RO) membrane filtration were evaluated, including: (i) membrane ultrafiltration (System I); (ii) dual media filter and granular activated carbon (GAC) adsorption (System II); (iii) dual medium filter and GAC with dosage of organic flocculant (15 mg/l to form filterable flocs).
TL;DR: In this paper, the dipole moment, the polarisability, the dielectric constant, the solubility in water, the octanol-water partition coefficient, the contact angle membrane/water, the Small number, the modified small number, molecular size, pKa, and the Taft parameter were selected for a detailed investigation of the adsorption process.
TL;DR: In this article, the ability of wine soluble constituents to foul organic cross-flow microfiltration membranes, to weight the respective impact of polysaccharides and polyphenols and to determine the incidence of membrane surface polarity in fouling was investigated.