Filtration Flux Research Articles

A novel anaerobic filter membrane bioreactor: prototype start-up and filtration assays.

Anaerobic digestion allows efficient treatment of high loaded wastewater, and membrane technology allows obtaining high quality effluents with complete biomass retention. However, high biomass concentration interferes with membrane fouling. In the present work, a new bioreactor that integrates an attached biomass anaerobic culture on a fixed bed and a submerged membrane has been started up. The recirculation between the digestion and filtration chambers is coupled to the gas-lift effect of the bubbling employed for the scouring of the membranes, avoiding the use or electromechanical pumps that damage the suspended biomass. The support material retains the biomass in the digestion tank despite the downwards flow, avoiding the submerged membrane contacting with a high concentrated suspension. This novel system, called an anaerobic filter membrane bioreactor was immediately started up, achieving chemical oxygen demand (COD) removal efficiencies of 96% at an organic loading rate (OLR) of 7 kg COD/m3·d. In order to select filtration flux, specific gas demand and filtration cycle duration, the results of 15 short term assays, eight hours for each one, is presented for fluxes between 15.7 and 17.7 L/m2·h, cycle duration between 10 and 30 minutes, and three levels of scouring. It was checked that reversible and irreversible fouling were directly related when dTMP/dt > 2.5 mbar/min.

Nano-porous SAPO-34 enhanced thin-film nanocomposite polymeric membrane: Simultaneously high water permeation and complete removal of cationic/anionic dyes from water

Thin-film nanocomposite (TFN) membranes were prepared by embedding nano-porous SAPO-34 nanoparticles in a polypyrrole thin-film layer polymerized on PES substrate. SEM, EDX, AFM, hydrophilicity, zeta potential and MWCO measurements were applied to verify characteristics of membranes. TFN membranes presented considerably higher pure water permeability (by more than 300%) due to high hydrophilicity and also nano-channels created in thin-film. Performance of TFN membranes were also evaluated by removal of different anionic and cationic dyes (methyl violet 6B, reactive blue 4 and acid blue 193) from water. TFN membranes effectively removed 100% of all dyes from feed aqueous solutions with a low concentration (50 mg/l). Moreover, TFN membrane prepared with the highest amount of nano-filler presented an elevated water flux in filtration of solutions containing each dyes (e.g. more than 500% for reactive blue 4), a reduced flux decline ratio (36%) and also a higher flux recovery ratio (85%) in comparison with the pristine thin-film membrane, consequently indicating high performance of TFN membranes and potential of recovery just after a simple water washing. TFN membranes also revealed an efficient performance in filtration of high concentrations of dye solutions as well as in treatment of a real wastewater produced by a weaving company.

Diatomite precoat filtration for wastewater treatment: Filtration performance and pollution mechanisms

As wastewater processing facilities deal with increasing amount in combination with enhanced environmental pressures, diatomite precoat filtration is becoming one of the promising methods for wastewater treatment. Filtration performance of diatomite precoat filtration with five different coating layer thicknesses for wastewater treatment was investigated in terms of permeate flux, fouling grade, filtration resistance, permeate quality and fouling reversibility. Pollution mechanism was revealed by fitting Hermia’s fouling models, detecting the pollutant transport and analyzing the changes in microstructure of diatomite. The optimal thickness of diatomite precoat filtration was 4mm, which exhibited that the highest average permeate flux was 16.53L/m2h, total fouling resistance reduced by 59.5%, and lowest cake water content was 55.1%. Contact angle measurement indicated that the fouling formed on the diatomite coating layer was highly reversible. Compared with individual fouling model, the combination of three Hermia’s fouling models at different stages fitted the flux data well. FESEM images of diatomite particles confirmed high filtration flux and supported the pollutant transport results. The superiority of diatomite precoat filtration in improving filtration performance and mitigation fouling was demonstrated. The present study could also provide an experimental basis for optimizing precoat filtration process.

Erythrocyte fouling on micro-engineered membranes.

Crossflow microfiltration of plasma from blood through microsieves in a microchannel is potentially useful in many biomedical applications, including clinically as a wearable water removal device under development by the authors. We report experiments that correlate filtration rates, transmembrane pressures (TMP) and shear rates during filtration through a microscopically high channel bounded by a low intrinsic resistance photolithographically-produced porous semiconductor membrane. These experiments allowed observation of erythrocyte behavior at the filtering surface and showed how their unique deformability properties dominated filtration resistance. At low filtration rates (corresponding to low TMP), they rolled along the filter surface, but at higher filtration rates (corresponding to higher TMP), they anchored themselves to the filter membrane, forming a self-assembled, incomplete monolayer. The incompleteness of the layer was an essential feature of the monolayer's ability to support sustainable filtration. Maximum steady-state filtration flux was a function of wall shear rate, as predicted by conventional crossflow filtration theory, but, contrary to theories based on convective diffusion, showed weak dependence of filtration on erythrocyte concentration. Post-filtration scanning electron micrographs revealed significant capture and deformation of erythrocytes in all filter pores in the range 0.25 to 2 μm diameter. We report filtration rates through these filters and describe a largely unrecognized mechanism that allows stable filtration in the presence of substantial cell layers.

The effect of infiltration flux on air counterflow and entrapment in a 2-D sand chamber

The effect of infiltration flux on air counterflow and entrapment in a 2-D sand chamber

Mitigating the aftermath of Malaysia's worst flood in 50 years: emergency drinking water supply with ultrafiltration

Abstract In December 2014, a massive flood hit northern states of Peninsular Malaysia causing severe damage to thousands of houses and leaving the area in a disastrous condition. Electricity and public piped water supplies were cut-off, as sub-stations and municipal water treatment plants were submerged in flood water. As part of Techkem Water's corporate social responsibility initiatives, mobile ultrafiltration membrane water treatment systems were deployed to provide emergency drinking water supplies to flood victims. Four types of mobile system were evaluated in this case study. The operational parameters of the systems such as feed water turbidity, system capacity, filtrate quality, filtration flux, footprint required and specific energy requirement details are presented. Each system has distinctive features that help to accommodate different site conditions.

A generalized groundwater fluctuation model based on precipitation for estimating water table levels of deep unconfined aquifers

A generalized water table fluctuation model based on precipitation was developed using a statistical conceptualization of unsaturated infiltration fluxes. A gamma distribution function was adopted as a transfer function due to its versatility in representing recharge rates with temporally dispersed infiltration fluxes, and a Laplace transformation was used to obtain an analytical solution. To prove the general applicability of the model, convergences with previous water table fluctuation models were shown as special cases. For validation, a few hypothetical cases were developed, where the applicability of the model to a wide range of unsaturated zone conditions was confirmed. For further validation, the model was applied to water table level estimations of three monitoring wells with considerably thick unsaturated zones on Jeju Island. The results show that the developed model represented the pattern of hydrographs from the two monitoring wells fairly well. The lag times from precipitation to recharge estimated from the developed system transfer function were found to agree with those from a conventional cross-correlation analysis. The developed model has the potential to be adopted for the hydraulic characterization of both saturated and unsaturated zones by being calibrated to actual data when extraneous and exogenous causes of water table fluctuation are limited. In addition, as it provides reference estimates, the model can be adopted as a tool for surveilling groundwater resources under hydraulically stressed conditions.

Biological hydrogen production via dark fermentation by using a side-stream dynamic membrane bioreactor: Effect of substrate concentration

This study investigates the possibility of using dynamic membranes (DMs) as a solid-liquid separation medium for fermentative H2 production under mesophilic conditions. In particular, the fouling behaviour of DM and H2 production are studied in response to different influent COD concentrations (10–100 gCOD L−1). The results demonstrate that the influent feed concentration significantly affects the filtration behaviour of DM. In fact, the decrease in influent COD concentration determined an improvement of both DM permeability and solids separation. In addition, high influent COD concentration (above 30 g L−1) and resulting high organic loading rates, favoured the accumulation of volatile fatty acids (VFA), leading to the inhibition of bio-hydrogen production. The results, thus, demonstrated that stable DM filtration and H2 production can be achieved by operating the bench-scale anaerobic DM bioreactor at low influent COD concentration (10–30 g L−1) and at an HRT of approximately 1 d. However, stable DM was achieved applying rather low filtration fluxes (approximately 2 L m−2 h−1).

Structural design of a rotating disk dynamic microfilter in improving filtration performance for fine particle removal

This study investigated the selection of optimal operating conditions and the design of efficient rotating disk structures for removing particles from seawater. The distributions of fluid velocity and shear stress on the membrane surface under various operating conditions were simulated using computational fluid dynamics. Type 1 rotating disk had two vans, Type 2 rotating disk had four vanes shaped identically to those of the Type 1 rotating disk, and Type 3 rotating disk had two vanes with circular orifices located at the center of each vane. The simulated results indicated that the disk rotation speed is the main factor affecting shear stress on the membrane surface. Cake mass and filtration flux were estimated from shear stress and were calculated using empirical equations. The results showed that flux in Type 1 increased by 28% when the disk rotation speed increased from 1000 to 3000 rpm; the installation of extra vanes caused an ineffective increase in flux at 3000 rpm. Although Type 2 exhibited the highest filtration performance and the lowest cake resistance, Type 3 is the optimal design because it exhibited the highest specific filtration flux among all tested rotating disk types. The rotating disk with two vanes with a circular orifice at a low disk rotation speed demonstrated the optimal design and operating conditions for removing particles from seawater, because it resulted in high filtration fluxes and relatively low power consumption.

Two‐Dimensional Probabilistic Infiltration Analysis in a Hillslope Using First‐Order Moment Approach

A first-order moment analysis method is introduced to evaluate the pore-water pressure variability within a hillslope due to spatial variability in saturated hydraulic conductivity (Ks ) during rainfall. The influences of the variance of the natural logarithm of Ks (ln Ks ), spatial structure anisotropy of ln Ks , and normalized vertical infiltration flux (q) on the evaluations of the pore-water pressure uncertainty are investigated. Results indicate different responses of pressure head variability in the unsaturated region and the saturated region. In the unsaturated region, a larger variance of ln Ks , a higher spatial structure anisotropy, and a smaller q lead to a larger variability in pressure head, while in the saturated region, the variability in pressure head increases with the increase of variance of ln Ks , the decrease of spatial structure anisotropy, or the increase of q. These variables have great impacts on the range of fluctuation of the phreatic surface within the hillslope. The influences of these three variables on the variance of pressure head within the saturated region are greater than those within the unsaturated region, and the variance of ln Ks has the greatest impact. These results yield useful insight into the effects of heterogeneity on pressure head and uncertainty associated with predicted flow field.

Glomerular Endothelium and its Impact on Glomerular Filtration Barrier in Diabetes: Are the Gaps Still Illusive?

Glomerular capillaries are lined with highly specialized fenestrated endothelium which are primarily responsible to regulate high flux filtration of fluid and small solutes. During filtration, plasma passes through the fenestrated endothelium and basement membrane before it reaches the slit diaphragm, a specialized type of intercellular junction that connects neighbouring podocytes. A PubMed search was done for recent articles on components of the glomerular filtration barrier such as glomerular endothelial cells, podocytes and glomerular basement membrane, and the effect of diabetes on these structures. Generally, the onset of kidney dysfunction in many diabetic patients is characterized by albuminuria/proteinuria, a pathophysiological event triggered by several factors including; (i) endothelial activation and shading of glycocalyx, (ii) loss of endothelial cell function, (ii) re-uptake of albumin by podocyte through a scavenger receptors and (iv) rearrangement of podocyte cytoskeleton. Howeover, as podocyte effacement does not always lead to proteinuria, the dynamic interplay between all constituents of the glomerular filtration barrier including podocytes, endothelial cells and the basement membrane may be fundamental for the effective filtration in healthy individuals. Thus, a putative cross-talk amongst podocytes, endothelial cells and the basement membrane in the homeostasis of glomerular function is envisaged. Although, the exact nature of this cross-talk remains to be clearly elucidated, it is possible that the interaction between: (i) glomerular endothelial cells and podocytes, (ii) glomerular endothelial cells and glomerular basement membrane, (iii) podocytes and glomerular basement membrane, and (iv) the simultaneous interaction amongst the three components collectively underpin effective filtration in healthy individuals. A comprehensive understanding of these different interactions still remains elusive. The elucidation of these multifaceted interactions will set the stage for greater understanding of the pathophysiology of kidney dysfunction.

Inverse correlation between vascular endothelial growth factor back-filtration and capillary filtration pressures

Vascular endothelial growth factor A (VEGF) is an essential growth factor during glomerular development and postnatal homeostasis. VEGF is secreted in high amounts by podocytes into the primary urine, back-filtered across the glomerular capillary wall to act on endothelial cells. So far it has been assumed that VEGF back-filtration is driven at a constant rate exclusively by diffusion. In the present work, glomerular VEGF back-filtration was investigated in vivo using a novel extended model based on endothelial fenestrations as surrogate marker for local VEGF concentrations. Single nephron glomerular filtration rate (SNGFR) and/or local filtration flux were manipulated by partial renal mass ablation, tubular ablation, and in transgenic mouse models of systemic or podocytic VEGF overexpression or reduction. Our study shows positive correlations between VEGF back-filtration and SNGFR as well as effective filtration rate under physiological conditions along individual glomerular capillaries in rodents and humans. Our results suggest that an additional force drives VEGF back-filtration, potentially regulated by SNGFR.

Production of a β-d-glucan-rich extract from Shiitake mushrooms (Lentinula edodes) by an extraction/microfiltration/reverse osmosis (nanofiltration) process

A pilot-scale process combining extraction of Shiitake mushroom (Lentinula edodes) powder in water (98 °C, 1 h), cross-flow microfiltration and reverse osmosis (nanofiltration) was performed to obtain β-glucan-rich extracts. Suspensions (45–80 L) obtained after 3 extractions were clarified by microfiltration reducing their turbidity to <1 NTU. Membrane flux was completely recovered after filtration. One of the clarified extracts was concentrated (to 6–7 L) by reverse osmosis (Nanomax95) and the other two by nanofiltration (Nanomax50 and ALNF99-2517). Different physicochemical parameters (permeate flux, total soluble substances, total suspended particles and electrical conductivity) were monitored during filtration and the bioactive compounds present in the obtained fractions (β-glucans, total carbohydrates, chitins, eritadenine, lenthionine, ergosterol) were analyzed. The more adequate membrane for Shiitake extract concentration was Nanomax50 because it showed higher filtration flux and higher values of bioactive compounds in the obtained extract than the extracts obtained with the other two membranes. This work describes a pilot-scale procedure for obtaining β-d-glucan-rich extracts from Lentinula edodes (Shiitake mushrooms). The extracts might be used in novel functional foods due to their high content in hypocholesterolemic compounds. The process combines extraction with boiling water, cross-flow membrane clarification and reverse osmosis/nanofiltration concentration of β-d-glucans. The procedure is scalable to industrial level.

Dynamic membrane bioreactor performance enhancement by powdered activated carbon addition: Evaluation of sludge morphological, aggregative and microbial properties

The effects of powdered activated carbon (PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor (DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane (DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes (protists and metazoans) and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC (BPAC), which promoted the enrichment of Acinetobacter (13.9%), Comamonas (2.9%), Flavobacterium (0.31%) and Pseudomonas (0.62%), all contributing to sludge flocs formation and several (such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.

Mineral Fertilizer and Manure Effects on Leached Inorganic Nitrogen, Nitrate Isotopic Composition, Phosphorus, and Dissolved Organic Carbon under Furrow Irrigation.

A better understanding of nutrient leaching in furrow irrigated agriculture is needed to optimize fertilizer use and avoid contamination of water supplies. In this field study (2003-2006), we measured deep percolation fluxes at 1.2-m depth and associated nutrient concentrations and mass losses from dairy manure nitrogen (N) or mineral N (urea, sodium nitrate [NaNO])-amended soils (372 kg available N ha in 4 yr) and nonamended controls and determined the δN-NO and δO-NO isotope ratios in the leached nitrate. Flow-weighted concentration means for individual irrigations varied widely, from near zero to as much as 250 mg L for NO-N, 480 μg L for dissolved reactive phosphorus (DRP), 43 mg L for dissolved organic C (DOC), and 390 mg L for chloride (Cl). Relative to other treatments, mineral fertilizer increased NO-N concentrations 2.6- to 3-fold and Cl concentrations 2.6- to 3.6-fold in deep leachate, particularly when NaNO was applied in 2004 and 2006, and produced maximum mean season-long NO-N and Cl losses. Manure and control treatments produced similar leachate nutrient mass losses, and for some irrigation periods, mineral fertilizer produced 85 and 97% lesser DRP losses and two times greater Cl losses compared with manure and control treatments. Four-year cumulative losses among treatments differed only for Cl. Isotopic composition of deep-leached nitrate indicates that both transformation and biologic cycling of mineral and manure N are rapid in these soils, which, with percolation volume, influence the amounts of NO-N and DOC leached. In light of the potential negative effects associated with either fertilizer type, and because even nonamended soils produced substantial amounts of leached NO-N (69.5 kg ha yr), management must minimize percolation water losses to limit nutrient losses from these fertilized, furrow-irrigated soils.

Intermittent flux from a sand filter for household wastewater and integrated solute transfer to the vadose zone.

Depending on the actual number of soil-based on-site wastewater treatment system (OWTS) in an area, on-site sanitation may be a significant source of pollutants and a threat to groundwater. Even in the case of a system functioning correctly, here, a sand filter substituted for the in-situ soil, as the treated effluent may reach to the water table, it is necessary evaluating in situ how much the sand and underneath soil respectively contribute to pollutant removal. On the plot of a household in a small rural community, the functioning of a real scale OWTS was monitored for 1.5years. This system, composed of a septic tank connected to a 5 × 5m2 and 0.7-m thick aerobic sand filter was equipped with soil hydrodynamic probes (water content and matrix potential) during construction. By using the instantaneous profile method of water content, the intermittent infiltrated flux was determined across the sand-pack according to position and time. Treated water infiltrates into underneath soil acting as post-treatment. Quality of interstitial liquid from the sand and the soil was analysed each month on a 12-h pumping sample obtained through porous plates. Results of water fluxes and concentrations provide an estimate of the annual flux to the vadose zone and groundwater of metals, nutrients and some organic micro-pollutants (parabens and triclosan) through the OWTS and subsoil.

Membrane development for improved performance of a magnetically induced vibration system for anaerobic sludge filtration

Abstract Magnetically induced membrane vibration as an alternative method to prevent membrane fouling was introduced in the past but membranes were never optimised for these systems. The starting hypothesis of this work is that a more open membrane, which entails a larger flux, can be used to fully benefit from these vibrations. This mechanical movement is expected to drastically reduce the foulant concentration at the membrane surface, thereby giving possibilities for a more open membrane. Polyvinylidene fluoride membranes were thus optimised by adding poly ethylene glycol as a pore-forming agent in different concentrations and with different molecular weight (MW) and by adjusting the polymer concentration in the casting solution. Overall performance of the modified membranes were evaluated using filtration indices (FIs) and a modified critical flux (CF) filtration method. A membrane composed of 12 wt% PVDF, 10 wt% 1000 Da PEG gave the best performance when the MMV was operated at 15 Hz in AnMBR sludge of 35 °C. The state of the art flux for anaerobic membrane bioreactors of 6 L/m 2 h could thus be improved by more than 60%. Surface pore size and membrane bulk porosity were identified as the two important parameters to optimise membranes for vibration systems.

Influence of graphene oxide sheets on the pore structure and filtration performance of a novel graphene oxide/silica/polyacrylonitrile mixed matrix membrane

The novel graphene oxide (GO)/silica (SiO2)/polyacrylonitrile (PAN) mixed matrix membranes (MMMs) with high filtration flux and excellent antifouling performance were designed and fabricated in situ by the method of non-solvent induced phase separation (NIPS) from the precursor of PAN hybridized with GO, tetraethoxysilane and 3-aminopropyltriethoxysilane. The influences of GO sheets on the pore and chemical structure, hydrophilic nature and filtration performance of derived GO/SiO2/PAN MMMs were investigated by the scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray, Fourier transform infrared spectrometer, pure water contact angles and filtration performance. Results indicated that in situ incorporation of GO sheets and SiO2 molecules into PAN matrix via NIPS reconstructs the porous structure of derived GO/SiO2/PAN MMMs with the upright finger-like holes, porous bottom, thinner top layer and high porosity. The spontaneous surface migration or segregation of hydrophilic GO sheets and SiO2 molecules as well as their synergistic interaction occurred during NIPS greatly ameliorate the top surface structure and property of derived membranes with smoother surface, uniform pore structure and good hydrophilicity. The derived GO/SiO2/PAN MMMs exhibit a high water filtration flux of 387 L m−2 h−1 with the bull serum albumin rejection rate up to 99% and significant enhancement of antifouling performance.

Effect of Phosphate on Ultrafiltration Membrane Performance After Predeposition of Fe3O4

The effect of predeposition of Fe3O4 on ultrafiltration (UF) processes has been widely studied in recent years. However, there have been no reports of effects of phosphate on the predeposition process. In this article, the fluxes of humic acid (HA) solutions filtered by Fe3O4+UF and Fe3O4+H2PO4−+UF were studied and filtered water was analyzed. Results indicate that the optimum concentration of Fe3O4 for the predeposition process was 0.45 g/L. Filtration fluxes of HA solutions using UF, Fe3O4+UF, and Fe3O4+H2PO4−+UF were 0.32, 0.52, and 0.41, respectively, after 10 min. Removal efficiencies of HA filtrated by UF, Fe3O4+UF, and Fe3O4+H2PO4−+UF were 32.6%, 41.1%, and 35.8%, respectively, according to dissolved organic matter results. After Fe3O4 adsorbed phosphate, the effect of Fe3O4 predeposition on removal of high and medium molecular weight HA was weaker. However, Fe3O4 predeposition enhanced removal of low molecular weight HA. Scanning electron microscopy and atomic force microscopy demonstrated that phosphate decreased compactness of the Fe3O4 predeposition layer. These data provide new insights into use of Fe3O4 predeposition in UF applications.

Study on Pollutant Removal Efficiency of Industrial Wastewater Using Submerged Anaerobic Membrane Bio-Reactor

The industrial effluents contain more organic pollutants, the most favorable option to treat this by anaerobic treatment process. In this study, a lab scale submerged anaerobic flat membrane bioreactor was operated with pumping operation for the treatment of tannery effluent. This Reactor was used to investigate the Residence Time Distribution and Rheology of the wastewater in the reactor under different Organic Loading Rate. Initially, treatment efficiency of the Submerged Membrane Bio – reactor was studied by monitoring various parameters (COD, TSS, TS, Alkalinity, VFA and pH). The COD removal efficiency was increasing from 66.67% to 88.89% invariably of the sludge retention inside the reactor. The results also showed that the membrane fouling was also occurring simultaneously, which is always predominant in any type of membrane treatment process. In order to decrease the membrane fouling rate, gas recirculation and effluent recirculation were employed and it proved efficient throughout the rheology study. The combined use of gas bubbles and periodic backwashing enables operation in high filtrate fluxes without seriously increasing the fouling resistance. RTD was maintained between 6 to 12 days with 18kg/m3/day was found to be optimum in efficient removal efficiency.