Showing papers on "Fouling published in 1997"
TL;DR: In this paper, the role of chemical and physical interactions in natural organic matter (NOM) fouling of nanofiltration membranes is systematically investigated, and it is demonstrated that the rate of fouling is controlled by an interplay between permeation drag and electrostatic double layer repulsion.
1,281 citations
TL;DR: In this article, the authors compared the fouling behavior of cellulose acetate and aromatic polyamide thin-film composite reverse osmosis (RO) membranes at identical initial permeation rates.
587 citations
TL;DR: In this article, a fiber optical device which provides real-time, on-line, in situ information non-destructively is proposed which can be adjusted to membrane modules, including microbiological and biochemical parameters, and the differentiation between scaling or organic fouling can be performed by FTIR-ATR spectroscopical analysis.
565 citations
TL;DR: In this paper, the most effective coagulant between ferric chloride and aluminium sulphate, optimal pH and most effective flocculant between anionic, cationic and nonionic polymers were examined in order to reduce the landfill leachates high fouling power, coagulation-flocculation is examined as reverse osmosis pretreatment.
405 citations
TL;DR: In this article, the effect of chemical and physical interactions on the fouling rate of cellulose acetate and aromatic polyamide composite reverse osmosis (RO) membranes by silica colloids is investigated.
Abstract: The effect of chemical and physical interactions on the fouling rate of cellulose acetate and aromatic polyamide composite reverse osmosis (RO) membranes by silica colloids is investigated. Results...
345 citations
TL;DR: In this article, five different chemically modified versions of polysulfone were prepared via two different homogeneous chemical reaction pathways, and each membrane was then exposed to deionized water, 0.08 g/l bovine serum albumin solution and deionised water using a standard filtration procedure to simulate protein fouling and cleaning potential.
296 citations
TL;DR: In this paper, α-alumina ceramic membranes (0.2 and 0.8 μm pore sizes) and a surface-modified polyacrylonitrile membrane ( 0.1 μm size) were tested with an oily water, containing various concentrations (250-1000 ppm) of heavy crude oil droplets of 1-10 μm diameter.
259 citations
TL;DR: In this paper, a general overview of the main factors in the fouling of processing equipment used for heating dairy fluids is given, and special attention is given to the parameters affecting the formation of both types of particles and how their formation can be retarded or prohibited.
244 citations
TL;DR: In this article, a review describes research into both the engineering and the chemical factors that lead to deposition of β-lactoglobulin in food fluids, and the rate of cleaning depends on both the deposit present and the type of chemical treatment used.
228 citations
TL;DR: In this article, a general overview of the basic physicochemical factors playing a role in fouling and some practical aspects related to the theoretical reasoning to help prevent or at least mitigate fouling are discussed.
177 citations
TL;DR: In this article, the authors explored the chemical and physical processes that cause fouling in organic mixtures under non-oxidative conditions, including autoxidation, polymerization and thermal decomposition.
TL;DR: In this paper, the authors examined the impact of several operating parameters on fouling including flux, concentrate velocity in hollow fibers, backwash frequency, and transmembrane pressure.
TL;DR: In this paper, the authors proposed a quantitative reaction model to optimize process conditions to reduce the fouling of equipment surfaces in milk processing, which can reduce more than 50% in many cases.
Abstract: Fouling of equipment surfaces in milk processing has been a costly problem for many years. However, with increasing knowledge of the fouling mechanism and the development of quantitative reaction models, it is becoming possible to optimize process conditions. Industrial application of the proposed approach shows that in many cases fouling can be reduced by more than 50%.
TL;DR: The results clearly demonstrate the importance of the protein structure, charge, and reactivity in determining the rate and extent of protein fouling during microfiltration.
Abstract: Recent studies of protein fouling have provided considerable insight into both the underlying fouling mechanisms and the mathematical description of the flux decline. However, most of the data have been obtained with a single model protein, making it difficult to generalize the results to commercially relevant process streams. Experiments were thus performed using a range of proteins with different physicochemical characteristics to determine the relationship between the protein structure and fouling behavior. Fouling in these systems occurred by two distinct mechanisms: deposition of large protein aggregates and chemical attachment of native proteins to the growing deposit. The chemical attachment generally occurred via the formation of intermolecular disulfide linkages involving a free sulfhydryl group in the native protein. Proteins without a free sulfhydryl group were typically unable to form these intermolecular linkages. The quasi-steady flux for the different proteins was proportional to the square of the protein surface charge density, consistent with a model in which protein deposition occurs when the drag force on the proteins associated with the convective filtrate flow is sufficient to overcome electrostatic repulsive interactions. These results clearly demonstrate the importance of the protein structure, charge, and reactivity in determining the rate and extent of protein fouling during microfiltration.
TL;DR: In this article, the development of stainless steel surfaces with low surface energy by ion implantation is described, which experience considerably reduced fouling without the inherent disadvantages of surface coatings, chemical additives and mechanical on-line cleaning methods.
TL;DR: In this article, an optimization of a backflushing technique combined with reverse asymmetric membranes (backshock) was used to avoid the fouling and concentration polarization problems, allowing the use of low linear velocities and resulting in low energy costs.
TL;DR: In this paper, a brief review of scale formation under boiling conditions and the deposition of wax crystals from organic liquids is presented, concluding with a brief discussion of the mechanism of crystallization on surfaces, and it is difficult to explain in mathematical terms.
TL;DR: In this article, the effect of operating parameters on the deposition of calcium sulphate on heat transfer surface during subcooled flow boiling was studied and a mechanistic model was suggested for prediction of fouling resistances, which is in good agreement with the experimental data.
TL;DR: In this article, an integrated membrane system pilot study compared microfiltration, ultrafiltration and conventional treatment as pretreatment strategies for surface water nanofiltration (BF) using spiral wound elements.
Abstract: An integrated membrane system pilot study compared microfiltration (MF), Ultrafiltration (UF), and conventional treatment as pretreatment strategies for surface water nanofiltration (BF) using spiral wound elements. MF and UF pretreatment resulted in lower NF fouling rates and longer cleaning intervals compared with those measured following conventional treatment. NF fouling rates evaluated under a wide range of hydrodynamic conditions following conventional treatment suggest NF fouling is more influenced by permeate flux than by feedwater recovery. NF was shownto be capable of meeting all current and anticipated trihalomethane and haloacetic acid regulations.
TL;DR: In this paper, the results of cleaning have been studied with flux and with charge characterization, and the results showed that the precleaned membranes had been modified by the detergent used.
TL;DR: The results show that the initial internal pore blocking can be attributed to protein adsorption while the long-time fouling should be caused mainly by solute-solute interactions.
TL;DR: The design of the cleaning head and displacement of netting away from the cleaner reduced the severity of scrubbing, but with increased contact between the brushes and netting the cleaner prevented significant fouling development over a 10-week period.
TL;DR: In this article, an experimental study of beer microfiltration has been carried out on ceramic membranes with the eventual aim of carrying this process through to the commercial scale, and the effect of surface hydrodynamics through flow pulsation had little impact on flux suggesting that pore blocking by in-depth adsorption/deposition was the dominant factor.
Abstract: An experimental study of beer microfiltration has been carried out on ceramic membranes with the eventual aim of carrying this process through to the commercial scale Enhancement of surface hydrodynamics through flow pulsation had little impact on flux suggesting that pore blocking by in-depth adsorption/deposition was the dominant factor and this was indeed found to be so The nature of the foulants has been determined by studying the filtration rates of beer treated with various enzymes which degrade potential foulant species Specific classes of carbohydrates and minerals have been identified as foulants In particular, pentosans (carbohydrates composed of 5 numbered sugar rings) make a major contribution A multi-stage backflush programme was developed and optimized in an attempt to achieve maximum pore clearance with minimal use of permeate and time Moreover, when backflush (BF) was employed, staged increases in trans-membrane pressure had a more positive impact on flux improvement The effect of membrane pore size on product quality and flux was also investigated in this work Use of the BF programme achieved a flux improvement of 400%
TL;DR: In this article, the Modified Fouling Index using ultrafiltration modules was used as a water quality indicator and to predict flux decline occurring in membrane filtration installations, which can be used to predict the flux decline in feed water.
TL;DR: In this article, the authors investigated the effects of calcium sulphate particles and alumina particles on calcium sulfate crystallization fouling in a plate heat exchanger and found that the presence of suspended particles in solutions significantly affects the crystallization rate.
Abstract: The presence of suspended particles in solutions significantly affects the crystallization rate. This study investigates the effects of calcium sulphate (crystallizing) particles and alumina (noncrystallizing) particles on calcium sulphate crystallization fouling in a plate heat exchanger. Calcium sulphate particles are formed during the preparation of calcium sulphate solution due to breakage of calcium sulphate crystals growing on the heat transfer surface. These suspended particles settle on the heat transfer surface and act as nuclei. The availability of extra nucleation sites increases the crystallization rate significantly. These particles can be removed with a filter, and the removal of the particles prevents this extra assistance available for crystallization. Therefore, the crystallization rate is reduced markedly. Alumina particles were purposely added during the preparation of calcium sulphate solutions. These particles attach loosely to the heat transfer surface compared with crystalline deposits which adhere strongly. Therefore, calcium sulphate crystals growing on these particles are removed easily. Also, alumina particles settling on the growth faces of calcium sulphate crystals may act as a distorting agent. This slows down the growth of the crystals.
TL;DR: In this article, the authors provided a scientific explanation for the operating principle of the electronic anti-fouling (EAF) technology, which produces an oscillating electric field via Faraday's law to provide necessary molecular agitation to dissolved mineral ions.
TL;DR: In this article, the authors used a heat flux sensor to measure the thermal resistance of whey protein deposits and their effective thermal conductivity in a concentric tube device using aqueous solutions of 3.5 wt% whey proteins concentrate.
TL;DR: The local phenomenology associated with membrane fouling has been investigated experimentally at laboratory scale for the crossflow microfiltration (CMF) of beer as mentioned in this paper, where two downstream membrane processes were involved: clarification and sterilisation of beer Fouling mechanisms were interpreted and compared for two types of beer (clarified beer and rough beer), filtered through a track-etched polycarbonate membrane.
Abstract: The local phenomenology associated with membrane fouling has been investigated experimentally at laboratory scale for the crossflow microfiltration (CMF) of beer Two downstream membrane processes were involved: clarification and sterilisation of beer Fouling mechanisms were interpreted and compared for two types of beer (clarified beer and rough beer), filtered through a track-etched 02 μm polycarbonate membrane Flux decay was analysed by using the combination of the constant pressure blocking filtration laws with the measurement of membrane resistances arranged in series It was found that for both types of beer the permeate flux was governed by two identical fouling mechanisms: an internal fouling of pores at the initial stages of filtration that conforms to the standard blocking model, followed by an external surface fouling conforming to the cake filtration model It was shown that the predominant membrane resistance arises from the build-up of a loosely bound and reversible fouling layer over the membrane surface (representing more than 80% of the total filtration resistance) Macrosolutes and colloids are likely to be involved both in the progressive pore plugging and in the external fouling layer (in combination with the yeast cells cake in the case of rough beer), because of their high tendency to interact with porous material Thus the relevance of using the so-called classical filtration laws for the investigation of fouling mechanisms in terms of total resistance of the membrane in beer CMF has been demonstrated
TL;DR: It is proposed that the microfiltration pore acts in a way similar to a pressure-relief valve where shear-induced protein denaturation has been observed, and narrowing of the pore in the immediate vicinity ofThe pore entrance is proposed.
TL;DR: In this paper, the authors focused on the filtration of an anaerobic suspension fed with acetic acid as the sole carbon source at 2 g/l TOC.