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In the classical contamination models, such as the gross-error (Huber and Tukey contamination model or Case-wise Contamination), observations are considered as the units to be identified as outliers or not. This model is very useful when the number of considered variables is moderately small. Alqallaf et al. [2009] shows the limits of this approach for a larger number of variables and introduced the Independent contamination model (Cell-wise Contamination) where now the cells are the units to be identified as outliers or not. One approach to deal, at the same time, with both type of contamination is filter out the contaminated cells from the data set and then apply a robust procedure able to handle case-wise outliers and missing values. Here we develop a general framework to build filters in any dimension based on statistical data depth functions. We show that previous approaches, e.g. Agostinelli et al. [2015a] and Leung et al. [2017], are special cases. We illustrate our method by using the half-space depth., Comment: 25 pages, 11 figures. TEST (2021)

Remote houses cannot use sewerage systems and so they must make their own arrangements for waste disposal. A solution is the use of ash depth filters which simultaneously trap nitrogen and phosphorus from human waste streams and all bacteria during long periods (750 ml per day for more than 6 weeks) of operation by filtration under gravity. Bacteria entering the filtration system, those trapped by the filter and the living material which eventually emerges if the system is operated till it eventually fails, are characterized. Reduction of bacterial numbers is achieved by two mechanisms: physical filtration and chemical sanitation.

Ash depth filters were developed which can simultaneously remove nitrogen, phosphorus and bacteria from human waste streams while simultaneously maintaining a flow rate which is acceptable for domestic use processing urine from one individual for 1 month if the filter bed has a volume of approximately 3 l. Nitrogen and phosphorus depletion is achieved by the formation of Struvite Enriched Ash, which can subsequently be used as a slow-release garden fertilizer. Depth filtration and sanitation by high pH removed all detectable bacteria from this home-based system.

Simultaneous Localization and Mapping (SLAM) has been widely applied in computer vision and robotics. For the dynamic environments which are very common in the real word, traditional visual SLAM system faces significant drop in localization and mapping accuracy due to the static world assumption. Recently, the semantic visual SLAM systems towards dynamic scenes have gradually attracted more and more attentions, which use the semantic information of images to help remove dynamic feature points. Existing semantic visual SLAM systems commonly detect the dynamic feature points by the semantic prior, geometry constraint or the combine of them, then map points corresponding to dynamic feature points are removed. In the visual SLAM framework, pose calculation is essentially around the 3D map points, so the essence of improving the accuracy of visual SLAM system is to build a more accurate and reliable map. These existing semantic visual SLAM systems are actually adopting an indirect way to acquire reliable map points, and several drawbacks exist. In this paper, we present SDF-SLAM: Semantic Depth Filter SLAM, a visual semantic SLAM system towards dynamic environments, which utilizes the technology of depth filter to directly judge whether a 3D map point is dynamic or not. First, the semantic information is integrated into the original pure geometry SLAM system by the semantic optical flow method to perform reliable map initialization. Second, design the semantic depth filter that satisfies the Gaussian Uniform mixture distribution to describe the inverse depth of each map point. Third, updating the inverse depth of 3D map point in a Bayesian estimation framework, and dividing the 3D map point into active one or inactive one. Last, only the active map points are utilized to achieve robust camera pose tracking. Experiments on TUM dataset demonstrate that our approach outperforms original ORB-SLAM2 and other state-of-the-art semantic SLAM systems.

Textile industry production processes generate one of the most highly polluted wastewaters in the world. Unfortunately, the field is also challenged by the availability of relatively cheap and highly effective technologies for wastewater purification. The application of natural zeolite as a depth filter offers an alternative and potential approach for textile wastewater treatment. The performance of a depth filter treatment system can be deeply affected by the column depth and the characteristics of the wastewater to be treated. Regrettably, the information on the potential of these filter materials for the purification of textile wastewater is still scarce. Therefore, this study investigated the potential applicability of natural zeolite in terms of column depth for the treatment of textile wastewater. From the analysis results, it was observed that the filtration efficiencies were relatively low (6.1 to 13.7%) for some parameters such as total dissolved solids, electrical conductivity, chemical oxygen demand, and sodium chloride when the wastewater samples were subjected to the 0.5 m column depth. Relatively high efficiency of 82 and 93.8% was observed from color and total suspended solids, respectively, when the wastewater samples were subjected to the 0.5 m column depth. Generally, the 0.75 m column depth achieved removal efficiencies ranging from 52.3% to 97.5%, whereas the 1 m column depth achieved removal efficiencies ranging from 86.9% to 99.4%. The highest removal efficiency was achieved with a combination of total suspended solids and 1 m column depth (99.4%). In summary, the treatment approach was observed to be highly effective for the removal of total suspended solids, with a 93.8% removal efficiency when the wastewater was subjected to the 0.5 m column depth, 97.5% for 0.75 m column depth, and 99.4% for 1 m column depth. Moreover, up to 218.233 mg of color per g of the filter material was captured. The results derived in this study provide useful information towards the potential applicability of natural zeolite in the textile wastewater treatment field.

A multiple length scale approach to the imaging and measurement of depth filters using X-ray computed tomography is described. Three different filter grades of varying nominal retention ratings were visualized in 3D and compared quantitatively based on porosity, pore size and tortuosity. Positional based analysis within the filters revealed greater voidage and average pore sizes in the upstream quartile before reducing progressively through the filter from the center to the downstream quartile, with these results visually supported by voidage distance maps in each case. Flow simulation to display tortuous paths that flow may take through internal voidage were examined.Digital reconstructions were capable of identifying individual constituents of voidage, cellulose and perlite inside each depth filter grade, with elemental analysis on upstream and downstream surfaces confirming perlite presence. Achieving an appropriate pixel size was of particular importance when optimizing imaging conditions for all grades examined. A 3 µm pixel size was capable of representing internal macropores of each filter structure; however, for the finest grade, an improvement to a 1 µm pixel size was required in order to resolve micropores and small perlite shards. Enhancing the pixel size resulted in average porosity measurements of 70% to 80% for all grades. Graphical abstract

Microfiltration membranes retain bacteria predominantly by size-exclusion. However, some empirical data points towards the fact, that alterations in flow rate as well as changes in the quality of adhesive interactions between the membrane surface and the bacteria can affect their retention. For parvo virus retaining normal flow virus-filters, systematic investigations have been undertaken to characterize the impact of flow alterations as well as modulations of particle-membrane interactions on virus particle retention. For depth filters used, e.g., for the clarification of fermentation broths, it is well known that alterations in flow rate typically lead to elevated levels of turbidity. This work adopts the acquired knowledge from virus- and depth-filters and investigates their applicability for bacteria retention by microfiltration membranes. It presents particle retention data for mycoplasma and Gram-negative and Gram-positive bacteria. Single layer flat sheet PES model microfiltration membranes with maximum pore sizes varying from 0.3 to 1.5 µm and an overall low retention were used in order to easily detect and differentiate their retention properties for the different particle species. The event of particle breakthrough is elucidated depending on the adsorptive character of the membrane surface, the pore size, and changes in flow rate including the interruption of flow. Moreover, this work investigates how the chemical and physical solution properties influence bacterial retention. These properties include the temperature of the fluid, the presence of a surfactant, the salt concentration and the pH. Flow interruptions using B. diminuta were also applied to commercially available PES sterilizing-grade microfiltration membranes showing no bacterial breakthrough.

The purpose of this study was to investigate the effect of alcoholic strength by volume (ASV) and storage conditions on turbidity in plum brandies. Different types of filter sheet were also tested for their effects on turbidity, as well as on the chemical composition and organoleptic characteristics of the distillates. The raw materials used were two plum distillates with initial ASVs of 76.77% v/v and 81.92% v/v. The distillates were diluted to alcohol contents of 37.5%, 40% and 50% v/v and stored under various conditions for 64 days. Filtration was performed using two depth filter sheets, with nominal retention rates of 0.40–0.48 μm and 0.80 μm, or with an activated carbon-based filter sheet. The lowest turbidity was observed in samples stored at ambient temperature with an ASV of 50% v/v. Reducing the alcohol content and storage temperature caused turbidity to increase. Samples prepared from distillate with an initial alcohol content of 76.77% v/v were characterized by significantly higher turbidity than those produced from spirit with an initial ASV of 81.92% v/v. Lowering the storage temperature resulted in a larger decrease in the concentration of volatile compounds after filtration. Use of an activated carbon filter sheet caused the greatest decrease in the majority of volatiles. Use of a filter sheet with a nominal retention rate of 0.80 μm led to the greatest improvement in the organoleptics of the tested plum distillates.

We report a comprehensive study on depth filter functionality by using a slurry, colloidal silica, used for chemical mechanical polishing process in semiconductor manufacturing. We show that the depth filters with nominal pore size ranging from 0.1 $\mu \text{m}$ to 0.5 $\mu \text{m}$ selectively reduces the concentration of ‘large’ particles up to 80%, and maintains other critical properties of slurry including solid content ratio, mean diameter of particles, pH, zeta potential, and conductivity. Furthermore, we find the particle size-dependent filter efficiency, and the stable and allowable pressure drop across the filters. The depth filtration efficiently reduces the large particle concentration in slurry, and thus could be useful for suppressing the associated manufacturing defects such as micro-scratches and pits on the polished wafers.

Depth filtration is a commonly-used bioprocessing unit operation for harvest clarification that reduces the levels of process- and product-related impurities such as cell debris, host-cell proteins, nucleic acids and protein aggregates. Since depth filters comprise multiple components, different functionalities may contribute to such retention, making the mechanisms by which different impurities are removed difficult to decouple. Here we probe the mechanisms by which double-stranded DNA (dsDNA) is retained on depth filter media by visualizing the distribution of fluorescently-labeled retained DNA on spent depth filter discs using confocal fluorescence microscopy. The extent of DNA displacement into the depth filter was found to increase with decreasing DNA length with increasing operational parameters such as wash volume and buffer ionic strength. Finally, using 5ethynyl-2'-deoxyuridine (EdU) to label DNA in dividing CHO cells, we showed that Chinese hamster ovary (CHO) cellular DNA in the lysate supernatant migrates deeper into the depth filter than the lysate re-suspended pellet, elucidating the role of the size of the DNA in its form as an impurity. Apart from aiding DNA purification and removal, our experimental approaches and findings can be leveraged in studying the transport and retention of nucleic acids and other impurities on depth filters at a small scale.

A self-standing filter with a porosity of 80% is prepared from naturally abundant cellulose biopolymer in its native state by water-based cationization and freeze-drying processes. The positive surface charge of the filter in a wide pH range favors its interaction with various nanoparticles (NPs), while its tortuous sheet structure builds a contact between cellulose nanofibers (CNF) and the NPs, and hinders them to pass through the filter. Unlike membranes used for the retention of NPs and viruses, the separation in the CNF filter is not only limited to its surface but occurs also in its interior even when the NPs are orders of magnitude smaller than the filter pores. Additional functionalities added to the filter enlarge the spectrum of NPs it can separate. NPs supported onto the filter can thereafter be utilized for the reduction of harmful chemicals into their benign form. The present filter concept may not only address shortcomings of the current membrane systems, but could offer a disruptive technology for the sustainable and universal water purification.

Tangential flow filtration is advantageous for bioreactor clarification as the permeate stream could be introduced directly to the subsequent product capture step. However, membrane fouling coupled with high product rejection has limited its use. Here, the performance of a reverse asymmetric hollow fiber membrane where the more open pore structure faces the feed stream and the barrier layer faces the permeate stream has been investigated. The open surface contains pores up to 40 μm in diameter while the tighter barrier layer has an average pore size of 0.4 μm. Filtration of Chinese hamster ovary cell feed streams has been investigated under conditions that could be expected in fed batch operations. The performance of the reverse asymmetric membrane is compared to that of symmetric hollow fiber membranes with nominal pore sizes of 0.2 and 0.65 μm. Laser scanning confocal microscopy was used to observe the locations of particle entrapment. The throughput of the reverse asymmetric membrane is significantly greater than the symmetric membranes. The membrane stabilizes an internal high permeability cake that acts like a depth filter. This stabilized cake can remove particulate matter that would foul the barrier layer if it faced the feed stream. An empirical model has been developed to describe the variation of flux and transmembrane pressure drop during filtration using reverse asymmetric membranes. Our results suggest that using a reverse asymmetric membrane could avoid severe flux decline associated with fouling of the barrier layer during bioreactor clarification.

For solid–liquid separation, filter meshes are still used across large areas today, as they offer a cost-effective alternative, for example, compared to membranes. However, particle interaction leads to a continuous blocking of the pores, which lowers the flow rate of the mesh and reduces its lifetime. This can be remedied by filter aids. In precoat filtration, these provide an already fully formed filter cake on the fabric, which acts as a surface and depth filter. This prevents interaction of the particles to be separated with the mesh and thus increases the service life of the mesh. In this work, the influence of a precoat layer with different fibre lengths of cellulose on the filtration behavior is investigated. A satin with a pore size of 11 µm is used as the filter medium. The effects of the precoat layer on the filter media resistance, the filter cake resistance, the turbidity impact, and the regenerability of the fabrics are investigated. This study shows an overview of the suitability of various cellulose fibres based on different aspects as filter aids for particles in ultrafine filtration.

The paper presents a novel instrumental analytical endotoxin quantification assay. It uses common analytical laboratory equipment (HPLC-FLD) and allows quantifying endotoxins (ETs) in different matrices from about 109 EU per mL down to about 40 EU per mL (RSE based). Test results are obtained in concentration units (e.g. ng ET per mL), which can then be converted to commonly used endotoxin units (EU per mL) in case of known pyrogenic activity. During endotoxin hydrolysis, the endotoxin specific rare sugar acid KDO is obtained quantitatively. After that, KDO is stoichiometrically reacted with DMB, which results in a highly fluorescent derivative. The mixture is separated using RP-HPLC followed by KDO-DMB quantification with a fluorescence detector. Based on the KDO content, the endotoxin content in the sample is calculated. The developed assay is economic and has a small error. Its applicability was demonstrated in applied research. ETs were quantified in purified bacterial biopolymers, which were produced by Gram-negative bacteria. Results were compared to LAL results obtained for the same samples. A high correlation was found between the results of both methods. Further, the new assay was utilized with high success during the development of novel endotoxin specific depth filters, which allow efficient, economic and sustainable ET removal during DSP. Those examples demonstrate that the new assay has the potential to complement the animal-based biological LAL pyrogenic quantification tests, which are accepted today by the major health authorities worldwide for the release of commercial pharmaceutical products.

Technologies suitable for the harvest clarification of cell cultures have experienced significant advancements in recent years. These advancements are motivated in part by increased cell densities and impurity levels, widespread industry adoption of single-use technologies, evolving regulatory landscapes, and a resurgence of perfusion cell cultures for continuous processing. This chapter details the major recent developments in the field of harvest clarification and includes discussions of core methods as well as emerging technologies. Core solid/liquid separation technologies such as centrifugation and depth filtration remain as cornerstones for the clarification of batch and fed-batch processes while microfiltration processes are being adopted for perfusion processes. Legacy methods, such as centrifugation have also advanced to incorporate new bowl designs for high density cell cultures, and process modifications have been made to improve product quality. Scale-down models for replicating shear and separation efficiencies have been reported. Recent developments for depth filters include new encapsulated devices, multistage depth filtration, and all-synthetic depth media grades. Tangential flow filtration and alternating tangential flow microfiltration methods are being adopted for high cell density perfusion processes. Recent developments in the areas of cell culture pretreatment and flocculation technologies, particle size characterization, and indirect analytical methods will also be discussed.

Despite the world practice, in the Russian Federation immunization against hemophilic infection is carried out only for the children from risk groups, which may be due to the lack of production of this vaccine in the Russian Federation. Therefore, the development of technology for the preparation of polyribosylribitol phosphate (PRP, the active substance of the Hib vaccine) remains relevant. Earlier, the employees of the federal state unitary enterprise “Saint-Petersburg scientific research institute of vaccines and serums and the enterprise for the production of bacterial preparations” of Federal medical and biologic agency of Russia isolated and identified the strain of Haemophilus influenzae SPB type b B-7884. The conditions for cultivation of the strain B-7884 and primary isolation of PRP from the culture liquid were arranged. The aim of the work was to study the possibility of excluding the centrifugation stage for separating H. influenzae SPB type b B-7884 biomass before clarification on the cascade of filter discs, and the development of subsequent stages of PRP isolation from the obtained intermediate product. Materials and methods. PRP isolation from an inactivated culture liquid of strain B-7884 was carried out by centrifugation, filtration, precipitation, homogenization, extraction under various conditions. The concentration of PRP in the intermediate products was determined by the orcinol method, the identity was determined by the latex agglutination test. Results and discussion. The optimal scheme for isolation and purification of the active pharmaceutical ingredient PRP, including filtration through the cascade of deep filters Zeta plus LP 60 (0.3–0.6 μm) and Zeta plus LP 90 (0.1–0.3 μm), concentration and diafiltration on ultrafiltration cassettes with nominal molecular weight cut-off of 30 kDa, precipitation with 10% cetyltrimethylammonium bromide solution (5% v/v), with subsequent homogenization of the obtained precipitate (in the presence of 12.5% of ethanol from the concentrate volume) and extraction (32.5% ethanol), filtration through depth filters Zeta Plus SP 30 and carbon filters Zeta Plus Carbon R53, and precipitation by 1.0% (v/v) 4.0 M sodium chloride solution and freezing at –(20 ± 2)°C, was developed. Conclusion. The obtained results will become the basis for the further development of the polysaccharide substance and allow us to proceed to the next stage in the development of the vaccine against Haemophilus influenzae type b – conjugation with the carrier protein.

Background Integrated continuous production technology is of great interest in biopharmaceutical industry. Efficient, flexible and cost effective methods for continuous cell removal have to be developed, before a fully continuous and integrated product train can be realized. The paper describes the development and testing of such an integrated continuous and disposable set-up for cell separation by flocculation combined with depth filtration. Results Screening of multiple flocculation agents, depth filters, and conditions demonstrated that the best performance was obtained with 0.0375% polydiallyldimethylammonium chloride (pDADMAC; a polycationic flocculation agent) in combination with Clarisolve® depth filters. Using this set-up, a 4-fold decrease of filtration area was achieved relative to standard filtration without flocculation, with yields of ≥97% and DNA depletion of up to 99%. Continuous operation was accomplished using a simple tubular reactor design with parallelization of the filtration. The reactor length was selected to allow a 13.2-min residence time, which was sufficient to complete flocculation in batch experiments. Continuous flocculation performance was monitored on-line using focused beam reflectance measurement. Filter switch cycles based on upstream pressure were controlled by in-line pressure sensors, and were stable from one filter to the next. Conclusion It was demonstrated that stable and efficient continuous flocculation associated with depth filtration can be easily accomplished using tubular reactors and parallelization. Continuous cell separation is essential for the development of fully continuous integrated process trains. This cost-efficient disposable design run in continuous mode significantly reduces facility foot print, process costs and enables great flexbility. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Depth filters are used throughout downstream bioprocessing, with specialized filter chemistries developed for removal of host cell proteins, DNA, and protein aggregates. These filters often show very broad breakthrough curves, but there have not been any previous analyses of this phenomenon. Protein breakthrough curves were evaluated for Ribonuclease A and α-chymotrypsin in two small-scale depth filter modules using PDH4 media containing diatomaceous earth. Computational fluid dynamics (CFD) simulations were developed, with flow in the porous media described using the modified Navier-Stokes equations incorporating a Brinkman flow term and a Langmuir binding model. The breakthrough curve in the stainless-steel module was much sharper than that in the commercial Supracap™ 50 capsule due to the more uniform axisymmetric flow field. The behavior in the Supracap™ 50 capsule was more complex, with multiple inflection points observed due to the different flow paths and the time-dependent saturation of the two layers of the depth filter media. These results provide important insights into the factors controlling protein binding/breakthrough in commercial depth filter modules.

Recent progress in mammalian cell culture process has resulted in significantly increased product titers, but also a substantial increase in process- and product-related impurities. Due to the diverse physicochemical properties of these impurities, there is constant need for new technologies that offer higher productivity and improved economics without sacrificing the process robustness required to meet final drug substance specifications. Here, we examined the use of new synthetic adsorptive hybrid filters (AHF) modified with the high binding capacity of quaternary amine (Emphaze™ AEX) and salt-tolerant biomimetic (Emphaze™ ST-AEX) ligands for clearance of process-related impurities like host cell protein (HCP), residual DNA, and virus. The potential to remove soluble aggregates was also examined. Our aim was to develop a mechanistic understanding of the interactions governing adsorptive removal of impurities during filtration by evaluating the effect of various filter types, feed streams, and process conditions on impurity removal. The ionic capacity of these filters was measured and correlated with their ability to remove impurities for multiple molecules. The ionic capacity of AHF significantly exceeded that of traditional adsorptive depth filters (ADF) by 40% for the Emphaze™ AEX and by 700% for the Emphaze™ ST-AEX, providing substantially higher reduction of soluble anionic impurities, including DNA, HCPs and model virus. Nevertheless, we determined that ADF with filter aid provided additional hydrophobic functionality that resulted in removal of higher molecular weight species than AHF. Implementing AHF demonstrated improved process-related impurity removal and viral clearance after Protein A chromatography and enabled a two-step purification process. The consequences of enhanced process performance are far reaching because it allows the downstream polishing train to be restructured and simplified, and chromatographic purity standards to be met with a reduced number of chromatographic steps.

Depth filtration is widely used for clarification of liquid feeds, including the purification of biopharmaceuticals. The performance characteristics of these depth filters can be strongly influenced by the local flow and pressure distribution within the filter capsule, but there is currently little information on these phenomena in commercial depth filter modules. This work used a combination of computational fluid dynamics (CFD), residence time distribution (RTD) measurements, and dye binding experiments to obtain detailed information on the pressure and flow distribution within a small-scale Supracap™ depth filtration capsule, containing two layers of depth filter media with different pore size, that is of high interest in bioprocessing. The results confirmed the presence of four distinct flow paths through the capsule, with less than 40% of the flow passing completely through both layers of the depth filter media and nearly 11% bypassing the large pore size prefilter layer. Model calculations were in good agreement with the measured RTD and images of dye binding, providing further confirmation of the flow phenomena. These studies provide important insights into the performance characteristics of these depth filters, while providing a framework that can be applied to analyze the pressure and flow distribution in other membrane and depth filtration modules.

Ultra scale‐down (USD) methods operating at the millilitre scale were used to characterise full‐scale processing of E. coli fermentation broths autolysed to different extents for release of a domain antibody. The focus was on the primary clarification stages involving continuous centrifugation followed by depth filtration. The performance of this sequence was predicted by USD studies to decrease significantly with increased extents of cell lysis. The use of polyethyleneimine reagent was studied to treat the lysed cell broth by precipitation of soluble contaminants such as DNA and flocculation of cell debris material. The USD studies were used to predict the impact of this treatment on the performance and here it was found that the fermentation could be run to maximum productivity using an acceptable clarification process (e.g., a centrifugation stage operating at 0.11 L/m2 equivalent gravity settling area per hour followed by a resultant required depth filter area of 0.07 m2/L supernatant). A range of USD predictions was verified at the pilot scale for centrifugation followed by depth filtration. © 2016 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 32:382–392, 2016

Depth filtration is employed in the production of many biological products. Although high throughput process development is available for most purification operations, options for high throughput depth filtration are limited. In this report, we describe the development and qualification of an ultra scale-down (USD) device for high throughput depth filtration. The system enables the parallel evaluation of eight single- or multi-layer depth filters approximately 0.2 cm2 in cross-sectional area, greater than two logs smaller than the smallest commercially available devices. To assess precision, scalability, modularity, and media heterogeneity in USD depth filtration, several types of adsorbent media were qualified in the USD device, with filtration performance compared to lab-scale devices (cross-sectional area: 23–25 cm2). The performance was further investigated with several high throughput clarity measurements, including particle characterization of filtrate fractions. Historically, depth filtration development has been limited by the amount of material required to run lab-scale filters. The described high throughput technology enables the screening of filter media early in development, optimization of operating parameters, and coupling of upstream operations to filtration performance. These high throughput capabilities will create efficiencies for development and manufacturing that were unattainable previously and create an important tool for screening novel biological entities.

Depth type composite filters are used to remove contaminants from liquids by combining mechanical entrapment and adsorption. Commonly, depth filters can adsorb either anionic or cationic charged contaminants, but not both, as well as filter micron-sized particles. Therefore, there is still a need to improve the existing depth filter performance. In this study, we developed a two-layer filters with enhanced functionality by spray coating an anionically charged cellulose nanofibre (CNF) layer onto a cationically charged depth filter layer. The depth filter layer was prepared via papermaking technique of vacuum filtration from wood pulp fibres, perlite adsorbent and cationic polyamide-amine epichlorohydrin (PAE) wet strength resin. The CNF coat weight ranged from 4 to 30 g per square metre (gsm). The two layer filters were proven to have triple functionality, capable of adsorbing anionic molecules in the cationic depth filter layer, while the anionic CNF layer could adsorb cationic molecules and was also a microfiltration membrane. A gradual increase in CNF coat weight improved filtration performance but decreased the filter flux. The optimum performance was found at an 8 gsm CNF coat weight, where the membrane layer rejected 80% of 5000 kDa molecular weight polyethylene glycol, at a flux of 133 Litres per square meter per hour (LMH) under 1.5 bar pressure, while still achieving a good breakthrough curve when absorbing cationic methylene blue dye.

Rapid depth filtration is the dominant pre-treatment technology in seawater desalination industry today. Optimizing the pre-treatment filter’s energy performance provides economies of scale in the total energy usage of desalination facilities on a broader sense. However, this objective remains difficult to achieve by far. In this study, we develop a numerical algorithm, termed as Dynamical Rapid Filtration Model (DRFM), to simulate the effective clogging dynamics occurring inside a depth filter which depends on a multitude of controlled and non-controlled operating parameters. DRFM quantifies the filtration kinetics with a modified Yao’s model to represent the particle removal mechanisms occurring within the simulated filter. A unique length scale is also introduced to account for the particle size effect on the filter’s energy loss rate incurred, i.e. its energy performance, during its effective filtration stage. Concurrently, we performed an experimental study with a lab-scale depth filter to develop a model equation for measuring its total contaminant mass removal rate ( R c ) due to effective clogging conditions. For a predicted R c transient profile, good agreement is obtained between the experimental results and predicted values from DRFM. We then extensively discuss on a novel DRFM hybrid model to optimize the filter’s energy performance which subsequently affects the filter’s optimized backwashing timing for achieving economies of scale. The simulation results from the hybrid model demonstrates on how various filter configurations can result in lower energy cost to effectively pre-treat each unit volume of intake seawater as compared to the current industrial average of 0.39 kWh / m 3 . Finally, we include a cost analysis to demonstrate on how the obtained economies of scale alleviates a portion of the total energy cost for each unit volume of desalinated water.

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High titer (>10 g/L) monoclonal antibody (mAb) cell culture processes are typically achieved by maintaining high viable cell densities over longer culture durations. A corresponding increase in the solids and sub-micron cellular debris particle levels are also observed. This higher burden of solids (≥15%) and sub-micron particles typically exceeds the capabilities of a continuous centrifuge to effectively remove the solids without a substantial loss of product and/or the capacity of the harvest filtration train (depth filter followed by membrane filter) used to clarify the centrate. We discuss here the use of a novel and simple two-polymer flocculation method used to harvest mAb from high cell mass cell culture processes. The addition of the polycationic polymer, poly diallyldimethylammonium chloride (PDADMAC) to the cell culture broth flocculates negatively-charged cells and cellular debris via an ionic interaction mechanism. Incorporation of a non-ionic polymer such as polyethylene glycol (PEG) into the PDADMAC flocculation results in larger flocculated particles with faster settling rate compared to PDADMAC-only flocculation. PDADMAC also flocculates the negatively-charged sub-micron particles to produce a feed stream with a significantly higher harvest filter train throughput compared to a typical centrifuged harvest feed stream. Cell culture process variability such as lactate production, cellular debris and cellular densities were investigated to determine the effect on flocculation. Since PDADMAC is cytotoxic, purification process clearance and toxicity assessment were performed.

The surface charging properties of silica micro-particles in aqueous solutions before and after surface chemical amination were measured and analysed using a new approach to the theoretical modelling of ion adsorption. The surface of aminated silica microspheres were further modified by chemical adsorption of l -cysteine groups to determine their ability to adsorb low levels of arsenic ions from aqueous solution. The adsorption of arsenic ions was observed both from changes in particle surface charge and from direct solution analysis, using ICP-OES. The results obtained indicate adsorption levels of about 2–5% of the cysteine surface density, from low-level arsenic solutions (i.e. less than 1 ppm). These initial results indicate that a suitable silica-based depth filter could be developed for the removal of low-level arsenic ions from contaminated water.

The impacts and dynamic penetration of nanoparticle suspension drops into porous filter membranes are studied experimentally and theoretically. This type of penetration is associated with hydrodynamic focusing and is radically different from the wettability-driven imbibition. In the case of hydrodynamic focusing water can penetrate into a non-wettable porous medium at very low values of the dynamic pressure associated with drop impact. Two types of membranes are used in the experiments: (i) glass fiber filter membrane wettable by the carrier fluid (water), and (ii) polytetrafluoroethylene (PTFE) depth filter membrane, non-wettable by the carrier fluid. The nanoparticle entrainment and deposition inside the membrane bulk is used to mostly visualize the ultimate penetration fronts by observing the cut cross-sections of the membranes, albeit also provide an insight into innovative applications like circuit printing on nonwovens. The deposition patterns inside the membranes are also linked to the drop splashing patterns at their front surfaces. The experimental results confirm that during the dynamic focusing water can penetrate into a non-wettable porous medium (PTFE). Water also penetrates by the same hydrodynamic focusing mechanism into the wettable glass fiber membrane, where it additionally spreads on a much longer time scale due to the wettability-driven flow. A theory explaining hydrodynamic focusing penetration of liquid into porous medium after drop impact is proposed. It is used to explain and predict water penetration into the non-wettable filter medium after drop impact, and the results are compared with the experimental data. Also the critical thickness of non-wettable membranes determined by dissipation of the kinetic energy in flow inside membrane is evaluated and compared with the experimental data.

This work investigates the performance and optimization of a hybrid process consisting of a fixed-bed adsorption (FBA) column and a dead-end filtration (DEF) cell for the removal of methylene blue (MB) from water. Granular activated carbon and cellulose acetate depth filter sheets were used as adsorbent and filter medium, respectively. Effects of four operation parameters (initial concentration, feed flowrate, bed length, and filter type) on the MB removal rate (RR) were investigated using breakthrough data analysis and response surface methodology. This RR (mass of MB removed per second) captures the removal capacity and separation rate, simultaneously. The maximum RR was found theoretically equal to 3.875 s−1 at the optimized conditions of initial concentration =39.86 mg/L, flowrate = 1.15 L/min, bed length =29.95 cm, and filter type = OS100, and validated with the experimental data with 99% agreement. The performance of the hybrid process operating at the optimal operation conditions was found to be superior to those of the individual FBA column and DEF cell. After 100 s from the process commencement, the RR obtained with the hybrid process was about 64% higher than that obtained with the FBA column and 30% higher than that obtained with the DEF cell.

Depth filter media are usually composed of multiple layers to attain optimal values of main filtration parameters such as pressure drop and particle collection efficiency (PCE). Understanding the performance of the single layers that make up the filter media can contribute to attaining these optimum values. For the purpose of this study, we have developed two samples of depth filter media, 2LM and 3LM, composed of two and three layers, respectively. Samples of the media and single layers have been prepared in flat sheet form. Filtration performance of these samples has been evaluated using a lab-scale flat sheet filter media test unit with KCl as the test aerosol. Results from these tests have been compared with those from an automated filter tester (AFT) with NaCl as the test aerosol. These media have been characterized based on filter media properties and data from the filtration performance tests and the effect of layers on filtration performance has been observed. Pressure drop data from the tests wit...

In this paper, we present an adaptive joint trilateral filter (AJTF), which consists of domain, range, and depth filters. The AJTF is used for the joint enhancement of images and depth maps, which is achieved by suppressing the noise and sharpening the edges simultaneously. For improving the sharpness of the image and depth map, the AJTF parameters, the offsets, and the standard deviations of the range and depth filters are determined in such a way that image edges that match well with depth edges are emphasized. To this end, pattern matching between local patches in the image and depth map is performed and the matching result is utilized to adjust the AJTF parameters. Experimental results show that the AJTF produces sharpness-enhanced images and depth maps without overshoot and undershoot artifacts, while successfully reducing noise as well. A comparison of the performance of the AJTF with those of conventional image and depth enhancement algorithms shows that the proposed algorithm is effective.

Considering the common use of sheet filtration for clarification of fruit brandies, the aim of this study was to evaluate the influence of its application on the stability and composition of volatile compounds of apricot brandy after cold stabilisation. Cold stabilisation treatment involved holding of the brandy at -1°C during 24 hours. Five depth filter sheets with the nominal retention rate of 0.3 μm, 0.5-0.7 μm, 0.7-1.0 μm, 1.0-2.0 μm and 2.5-4.0 μm, were tested in the study. It was shown that all assessed filter sheets were efficient in removing chill haze by significantly reducing the content of fatty acid esters (primarily ethyl palmitate and ethyl laurate). Other volatile and aromatic compounds were not significantly influenced by the applied treatments. However, the filter sheets with higher nominal retention rate (> 0.7 μm), had a smaller impact on the sensory characteristics of the apricot brandy. The re-exposure to lower temperatures did not lead to chill haze formation in any sample obtained after sheet filtration. [Projekat Ministarstva nauke Republike Srbije, br. TR-31002]

Part 6: Image Understanding; International audience; 3D reconstruction is an important technique in the environmental perception and rehabilitation process. With the help of active depth-aware sensors, such as Kinect from Microsoft and SwissRanger, the depth map can be captured at the video frame rate together with color information to enable the real-time reconstruction. Particularly, it features prominently in the activity recognition and remote rehabilitation. Unfortunately, the coarseness of the depth map make it difficult to extract the detailed information in 3D reconstruction of the scene and tracking of thin objects. Especially, geometric distortions occur around the edge of an object. Therefore, this paper presents a confidence weighted real-time depth filter for the edge recovery to reduce the extra artifacts due to the uncertainty of each depth measurement. Also the intensity of depth map is taken into account to optimize the weighting term in the algorithm. Moreover, the GPU implementation guarantees the high computational efficiency for the real-time applications. Experimental results are shown to illustrate the performance of the proposed method by the comparisons with the traditional methods.

Conventional foodborne pathogen assays currently used in the food industry often require long culture enrichments to increase pathogen levels so they can be detected. Even using sensitive real-time PCR assays, culture enrichment at least overnight is necessary especially for detection of pathogens with slow growth rates such as Listeria monocytogenes. To eliminate this cumbersome enrichment step and detect minute amounts of pathogens within 1 day, filter-based pathogen enrichment technology was developed utilizing a unique combination of glass fiber depth filter and porous filter aid materials to efficiently separate pathogens from food homogenates and avoid filter clogging by food particles. After pathogen immobilization in depth filters, only viable pathogens were selectively collected in a small volume of growth medium via microbial multiplication and migration; nonviable pathogens remained inside the filters. By assaying viable pathogens using real-time PCRs, multiple species of foodborne pathogens were detected, including L. monocytogenes, Salmonella enterica, and Escherichia coli O157:H7, at around 1 CFU/ml or 1 CFU/g in various food samples. This filter-based pathogen enrichment technology is a unique bacterial enrichment alternative to the conventional culture enrichment step and can significantly shorten the time necessary to obtain assay results.

Depth filter microfiltration membranes produced from biodegradable poly( l -lactic acid) (PLLA) are reported in this paper. The asymmetric porous membranes reported here were formed via a process that combined nonsolvent-induced and thermally induced phase separation. The membranes served as efficient and rapid depth filters to retain bacterial cells when cell suspensions were filtered from the porous or rough side of the membrane, while serving as screen filters when the suspension was fed from the smooth skin side. After use, the depth filters were disposed of by non-enzymatic degradation – a process that was significantly accelerated in wet conditions at 60 °C, conditions under which composting is usually operated. The fact that the PLLA depth filters reported here can be disposed of by composting will help reduce industrial wastes in biochemical and food industries when they are used as a pre-filter.

This paper explores the viability of developing high surface area pre-filters through electrospinning. Pre-filters are regularly used in removing particulate contaminants that can have a deleterious effect on downstream membrane elements such as ultrafiltration and nanofiltration. They should possess high internal surface area and thus sub-micron size fibers are ideal. In this study, polysulfone nanofibers were electrospun into membranes and their ability to remove micro-particles from solution was investigated. The nanofibrous membranes possess high porosity together with high surface area to produce high flux pre-filters with high loading capacity. The membrane had a bubble-point of 4.6 μm and was able to remove above 99% of 10, 8 and 7 μm particles without any permanent fouling. However, the membrane was observed to foul irreversibly by 2 and 1 μm particles with a ‘cake-layer’ forming on the membrane surface. Below 1 μm, the membrane behaved as a depth filter with 0.5 and 0.1 μm particles being attracted onto the nanofiber surface. This study highlights that nanofibers do have potential as pre-filters for particulate removal. Such nanofibrous pre-filters can be used in various applications such as removal of micro-particles from waste-water, prior to ultrafiltration or nanofiltration membranes, to prolong the life of these membranes.

In the production of biopharmaceuticals disk‐stack centrifugation is widely used as a harvest step for the removal of cells and cellular debris. Depth filters followed by sterile filters are often then employed to remove residual solids remaining in the centrate. Process development of centrifugation is usually conducted at pilot‐scale so as to mimic the commercial scale equipment but this method requires large quantities of cell culture and significant levels of effort for successful characterization. A scale‐down approach based upon the use of a shear device and a bench‐top centrifuge has been extended in this work towards a preparative methodology that successfully predicts the performance of the continuous centrifuge and polishing filters. The use of this methodology allows the effects of cell culture conditions and large‐scale centrifugal process parameters on subsequent filtration performance to be assessed at an early stage of process development where material availability is limited. Biotechnol. Bioeng. 2016;113: 1934–1941. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

The clarification of biological feed stocks during the production of biopharmaceutical proteins is challenging when large quantities of particles must be removed, e.g., when processing crude plant extracts. Single-use depth filters are often preferred for clarification because they are simple to integrate and have a good safety profile. However, the combination of filter layers must be optimized in terms of nominal retention ratings to account for the unique particle size distribution in each feed stock. We have recently shown that predictive models can facilitate filter screening and the selection of appropriate filter layers. Here we expand our previous study by testing several filters with different retention ratings. The filters typically contain diatomite to facilitate the removal of fine particles. However, diatomite can interfere with the recovery of large biopharmaceutical molecules such as virus-like particles and aggregated proteins. Therefore, we also tested filtration devices composed solely of cellulose fibers and cohesive resin. The capacities of both filter types varied from 10 to 50 L m(-2) when challenged with tobacco leaf extracts, but the filtrate turbidity was ~500-fold lower (~3.5 NTU) when diatomite filters were used. We also tested pre-coat filtration with dispersed diatomite, which achieved capacities of up to 120 L m(-2) with turbidities of ~100 NTU using bulk plant extracts, and in contrast to the other depth filters did not require an upstream bag filter. Single pre-coat filtration devices can thus replace combinations of bag and depth filters to simplify the processing of plant extracts, potentially saving on time, labor and consumables. The protein concentrations of TSP, DsRed and antibody 2G12 were not affected by pre-coat filtration, indicating its general applicability during the manufacture of plant-derived biopharmaceutical proteins.