An investigation into the microbial clogging potential of selected filter media as a result of biodegradation of a high-strength sulphate-rich alkaline leachate

The research examines the potential for bio-clogging in filter packs containing fine sand of the type typically used in extraction wells for pumping leachates containing fine particulate matter, such as cement kiln dust (CKD). Three filter media with different particle sizes were used: 1.7–4.75, 0.35–1.0, and 0.235–0.45 mm. Each sand filter was tested using a leachate recirculating column reactor with a free drainage layer, on top of which was placed the filtration medium which was kept saturated and at a positive hydrostatic head by a 2-l reservoir of leachate. The leachate was collected from a landfill site that had been used for the co-disposal of municipal solid waste (MSW) and CKD. The leachate used was filtered by passing through a Whatman GFA filter paper before being added to the reactors in order to eliminate as far as possible the non-biological clogging which might have resulted from the introduction of particulate matter in the form of CKD. The filters and a control experiment were run under anaerobic conditions at 35 °C. The bio-clogging potential was observed by taking differential manometer readings from manometers located in the drainage and reservoir sections of the reactor. No clogging was detected using the coarser of the filter media, but there was some clogging when a finer filter medium was used. Head space gas analysis indicated that methanogenic activity was inhibited and analysis of the liquid phase indicated that the microbial process responsible for removal of chemical oxygen demand (COD) was principally one of sulphate reduction.     

Analysis of flow acceleration during erythrocyte filtration: Dependence of hematocrit and cell rigidity

At flow onset the blood filtration rate accelerates to a steady state, this may affect the interpretation of red blood cell (RBC) filterability. We studied the acceleration of flow while the pressure is built up across the filter to analyse effects of various hematocrits and RBC rigidity by glutaraldehyde (GA) hardening. This was analysed by a new filtration system with high time resolution and unlimited filtration volume. The system uses a digital balance that samples the accumulated weight (e.g., filtration rate through 5 μm Nuclepore membranes) with on-line computer communication. The filtration is computer controlled via a pneumatic valve. White blood cells (WBC) were removed prior to filtration by a WBC-eliminating filter to avoid clogging artifacts. When flow is initiated a steady state is reached at 0.3–0.4 s. This timing was also tested and confirmed by a video monitoring technique of filtration flow into a horizontal pipette. The digital balance has a mathematical function to reduce the effects of vibration noise; when this function was activated the apparent acceleration was retarded to 1.2 s. With any of these techniques the steady state timing did not vary with the hematocrit, however, the volume of filtered suspension during acceleration varied with both the hematocrit and the GA hardening (p < 0.001). Extrapolation to yield the initial filtration rate from the relative flow curve (RBC suspension divided by buffer flow) varied depending on if the acceleration phase was included or not. In the most unfavourable situation, with GA-hardened RBC, this difference was 340% (p < 0.01). The slope to calculate clogging rate was affected in a similar way. Moreover, with the most GA-hardened RBC a delay in flow onset was observed with this technique. The acceleration phenomenon may cause artifacts in systems employing volumederived filtration kinetics because of fixed volumes of filtrated medium.     

Use of polyester leukocyte elimination filters in blood filterability research

We tested a new routine to eliminate leukocytes for blood rheology measurements using commercial leukocyte absorbing filters (here PALL RC400). These filters were punched out and fitted in smaller chambers through which blood was filtered under controlled suction pressure (< 30 mm Hg). This technique resulted in a very effective leukocyte elimination to 0.0022% but also a platelet reduction to 0.2%. The process causes a small but significant hemolysis with free hemoglobin, of the order of 0.06% of the filtered erythrocytes. A small fraction of the erythrocytes were retained in the filter, versus plasma, to reduce the hematocrit on the order of 1.4%. The leukocyte filtration did not cause any detectable functional trauma to the erythrocytes, measured as micro-pore filterability of normal and glutaraldehyde (GA) hardened erythrocytes. However, when 10% of the erythrocytes were hardened with GA, which caused an increase in pore clogging slope (p < 0.05), the additional passage through the leukocyte elimination filter removed this measured change in clogging. This observation suggests that the leukocyte elimination filter may selectively remove, not only leukocytes and platelets, but also hardened erythrocytes. Reticulocyte counting did not reveal any selective removal of young erythrocytes. In general, we find the presented method reproducible, efficient and easy for eliminating leukocytes for blood rheology research although the risk of removing undeformable erythrocytes must be considered.     

Evaluation of a sterile filtration process for viral vaccines using a model nanoparticle suspension

There is growing interest in the development of new vaccines based on live‐attenuated viruses (LAVs) and virus‐like particles. The large size of these vaccines, typically 100–400 nm, significantly complicates the use of sterile filtration. The objectives of this study are to examine the performance of several commercial sterile filters for filtration of a cytomegalovirus vaccine candidate (referred to as the LAV) and to develop and evaluate the use of a model nanoparticle suspension to perform a more quantitative assessment. Data obtained with a mixture of 200‐ and 300‐nm fluorescent particles provided yield and pressure profiles that captured the behavior of the viral vaccine. This included the excellent performance of the Sartorius Sartobran P filter, which provided greater than 80% yield of both the vaccine and model particles even though the average particle size was more than 250 nm. The particle yield for the Sartobran P was independent of filtrate flux above 200 L/m²/h, but increased with increasing particle concentration, varying from less than 10% at concentrations around 10⁷ particles/ml to more than 80% at concentrations above 10¹⁰ particles/ml due to saturation of particle capture/binding sites within the filter. These results provide important insights into the factors controlling transmission and fouling during sterile filtration of large vaccine products.     

Dewatering of phosphorus extracted from liquid swine waste

Phosphorus (P) recovery from liquid swine manure is an attractive technology when on-farm application of liquid swine manure is not an option. We developed a technology that enables separation of this P, but its high moisture content makes transportation difficult. In this work, we investigated dewatering procedures to concentrate the P product. Sludge rich in calcium phosphate (> 20% P2O5) was obtained using a field prototype, and it was further dewatered using a combination of polymer treatment and filter bags. Anionic polyacrylamide polymer treatment (> or = 20 mg/L) was effective to flocculate the P-rich sludge, which enhanced filtration and dewatering. Without polymer, filtration was incomplete due to clogging of filters. Non-woven polypropylene and monofilament filter bag fabrics with mesh size < or = 200 microm retained > 99% of suspended solids and total P. Solids content dramatically increased from about 1.5% to > 90%. These dewatered solids can be transported more economically off the farm for use as a valuable fertilizer material.     

Computational Fluid Dynamics of Fish Gill Rakers During Crossflow Filtration

We study crossflow filtration mechanisms in suspension-feeding fishes using computational fluid dynamics to model fluid flow and food particle movement in the vicinity of the gill rakers. During industrial and biological crossflow filtration, particles are retained when they remain suspended in the mainstream flow traveling across the filter surface rather than traveling perpendicularly to the filter. Here we identify physical parameters and hydrodynamic processes that determine food particle movement and retention inside the fish oral cavity. We demonstrate how five variables affect flow patterns and particle trajectories: (1) flow speed inside the fish oral cavity, (2) incident angle of the flow approaching the filter, (3) dimensions of filter structures, (4) particle size, and (5) particle density. Our study indicates that empirical experiments are needed to quantify flow parameters inside the oral cavity, and morphological research is needed to quantify dimensions of the filter apparatus such as gill rakers, the gaps between rakers, and downstream barriers. Ecological studies on suspension-feeding fishes are also needed to quantify food particle size and density, as these variables can affect particle retention due to hydrodynamic processes during crossflow filtration.     

Effect of particle size distribution on filtration performance of cell culture medium

Cell culture media used in CHO-based biologic processes are typically sterile filtered to prevent microbial contamination prior to inoculation. In this study, the impact of common sterile filter throughput on a different, commercially available cell culture media was evaluated from the intermediate-adsorption fouling model of the filtration model. The key particle size range for optimum filter performance was discussed and identified by measuring the submicron order particle size distribution. It may be possible to predict the performance of filter capacity with size-exclusive separation by understanding the media particle counts and size distribution.     

Multi-laboratory evaluation of procedures for reducing the volume of cord blood: influence on cell recoveries

BACKGROUND: Various procedures can be used to isolate stem and progenitor cells from cord blood. This study evaluated the hydroxyethyl starch sedimentation (HES) with two centrifugation steps, and the top and bottom (T&B) isolation of buffy coat following a single centrifugation, and two filter systems for processing cord blood, one developed by Asahi Kasei Medical (filter A) and the second by Terumo (filter B). METHODS: Each of seven laboratories was randomly assigned the evaluation of either the HES or T&B method and one of the filter methods (n=8 cord blood units, per laboratory, for each method). The leukocyte-containing fraction with the stem/progenitor cells was recovered from the filters by reverse flushing. Utilizing the routine traditional processing and testing procedures of each laboratory, in vitro parameters were determined, with samples obtained after collection, after processing and after freezing/thawing. The results were expressed as the percentage recovery of viable cells in processed vs. collected samples (performance 1; PF1) and in thawed vs. processed samples (performance 2; PF2). The composite results obtained by the seven laboratories were summarized. RESULTS: The median PF1 percentage recovery of total nucleated cells (TNC) was comparable with both traditional methods (HES 79%, T&B 86%) and statistically reduced with both filtration procedures (filter A 58%, filter B 61%). Mononuclear cell (MNC) PF1 recovery was highest statistically with the T&B method (91%) and reduced on using filter A (77%) and filter B (70%) and the HES method (72%). CD34+ cell recovery was judged to be essentially comparable with the four methods, although the range of unit recoveries differed. The percentage recovery of TNC and MNC in PF1 was influenced by the volume of the collected cord blood, especially with use of the filtration procedures. This correlated with TNC content. A greater percentage of red cells and platelets was removed during processing with both filter methods. The time to process cord blood preparations with filter A was significantly shorter than the other methods. Processing with the HES method took the longest time. The recoveries for TNC, MNC and CD34+ cells in PF2 did not appear to be influenced by the specific processing procedure. DISCUSSION: These data indicate that filters that capture stem and progenitor cells may be an appropriate methodology for processing cord blood collected for banking.     

Pilot plant scale extraction of alginates from Macrocystis pyrifera. 2. Studies on extraction conditions andmethods of separating the alkaline-insoluble residue

The effect of temperature (70, 80, 90 ^°C) and time (1–9 h) during the alkaline extraction step on alginate yield and quality were studied. The alginate yield increased with time and maximum yield was obtained after 3.5 h treatment, ranging from19.4% at 70 ^°C to 21.9% at 90 ^°C. The viscosity of the alginate produced was inversely correlated with the temperature and time. At70 ^°C the slope of the curve was almost zero(753 to 923 mPa s); at 90 ^°C the viscosity loss was 154 mPa s per hour during the first two hours, reducing from 523 to 86 mPa s after 5 h; 80 ^°C yielded values between those for 70 ^°C and90 ^°C. The best conditions for alkaline extraction were using pH 10 at 80 ^°C for two hours. The curves obtained gave useful information for controlling the viscosity of the alginate during production. It was found that viscosity of the paste formed during alkaline extraction (`process viscosity') was the best parameter to determine there action rate during extraction. Alginate yield increased during filtration time from 17.6% to 23.7%after 55 min at 70 ^°C. In this step the viscosity of the alginate obtained remained almost constant (522–610 mPa s), indicating no degradation of the products during filtration. The best dilution to filter the alginate extract was obtained at 45 mPa s. Diatomaceous earth (Celite) and expanded lava(Perlite) were tested as filter aids. Expanded lava was the best filter aid, using 1 kg per kilogram of alginate produced. Three methods were studied to separate the alkaline-insoluble residues after extraction: filtration, centrifugation, flocculation, and combinations of them. The best system found was filtration with flocculant in a rotary vacuum filter, with a knife advance of 0.1 mm every 3.5 seconds and drum rotation of 2 rpm, yielding an average filtration flow rate of 10.5 L min^-1. This revised version was published online in August 2006 with corrections to the Cover Date.     

水平潜流人工湿地堵塞初期微生物群落结构变化

为了寻找合适的湿地堵塞监测指标,文章通过运行4组湿地装置来模拟水平潜流人工湿地堵塞的过程,并研究人工湿地中微生物群落在湿地堵塞初期的响应。在人工湿地反应器运行过程中,定期监测基质过滤速率与人工湿地处理性能,包括化学需氧量(COD)、总氮(TN)和总磷(TP)去除效率,同时应用高通量测序技术测定并分析湿地反应器中微生物群落结构组成与多样性。结果表明:随着堵塞的形成,在4组人工湿地中,基质过滤速率和TP的去除效率持续下降,而COD和TN的去除效率分别为50%—85%和10%—20%; 16S rDNA测序结果表明堵塞会降低细菌群落的丰富度和多样性;人工湿地系统中的优势菌门主要是变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和绿弯菌门(Chloroflexi)等,且当湿地进入堵塞初期后,变形菌门丰度明显增加,具体表现为其门下的反硝化细菌属(Thauera、Zoogloea和Rhizobium)丰度显著增加,此外厚壁菌门和绿弯菌门的有机物降解菌属(Clostridium sensu stricto、Gracilibacter和Levilinea)的丰度也明显增加,这...     

Discrete particle simulations predicting mixing behavior of solid substrate particles in a rotating drum fermenter.

A soft-sphere discrete particle model was used to simulate mixing behavior of solid substrate particles in a slow rotating drum for solid-state fermentation. In this approach, forces acting on and subsequent motion of individual particles can be predicted. The (2D) simulations were qualitatively and quantitatively validated by mixing experiments using video and image analysis techniques. It was found that the simulations successfully predicted the mixing progress as a function of the degree of filling and size of the drum. It is shown that only relatively large, straight baffles perpendicular to the drum wall (67% of the drum radius) increase the mixing performance of the rotating drum. Considering the different aspects of mixing dealt with in this work, it is concluded that the soft sphere discrete particle model can serve as a valuable tool for investigating mixing of solid substrate particles. Finally, it is expected that this model may evolve into a potential tool for design and scale-up of mixed solid-state fermenters.     

Clogging of the glomerular basement membrane

The negative charges of the sulfated glycosaminoglycans (GAGs) of the glomerular basement membrane (GBM) were differentially neutralized by perfusin with high molarity buffers in order to determine whether or not these charges protect the GBM from being clogged by circulating plasma macromolecules. Progressive elimination of the negative charges resulted in clogging of the GBM by perfused native ferritin (NF) and bovine serum albumin as evidenced ultrastructurally by the increase in accumulation of NF in the GBM. In addition, the permeability of the GBM to 125I-insulin, a macromolecule which is normally freely permeable, and the glomerular filtration rate (as determined by [3H]inulin clearance) were markedly reduced after the GBM had been clogged with NF in the presence of high molarity buffer, thereby indicating that clogging severely reduces the ability of the GMB to act as a selective filter. These findings are consistent with the idea that the sulfated GAGs of the GBM serve as anticlogging agents.     

Capture of bacteria from fermentation broth by body feed filtration: a solved problem?

The direct capture of bacteria produced in high cell density fermentation by filtration is not possible once the milliliter-scale has been surpassed. Filtration in the presence of a filter aid (body feed filtration) constitutes a putative and scalable alternative, but only if conditions proposed by industry for large-scale filtration processes, namely, flow rates (for aqueous solutions) in the range of 500-1,500 L/(m(2) x h) and a filter aid concentration of 相似文献   

Three-dimensional simulation of grain mixing in three different rotating drum designs for solid-state fermentation

A previously published two-dimensional discrete particle simulation model for radial mixing behavior of various slowly rotating drums for solid-state fermentation (SSF) has been extended to a three-dimensional model that also predicts axial mixing. Radial and axial mixing characteristics were predicted for three different drum designs: (1) without baffles; (2) with straight baffles; and (3) with curved baffles. The axial mixing behavior was studied experimentally with video- and image-analysis techniques. In the drum without baffles and with curved baffles the predicted mixing behavior matched the observed behavior adequately. The predicted axial mixing behavior in the drum with straight baffles was predicted less accurately, and it appeared to be strongly dependent on particle rotation, which was in contrast to the other drum designs. In the drum with curved baffles complete mixing in the radial and axial direction was achieved much faster than in the other designs; that is, it was already achieved after three to four rotations. This drum design may therefore be very well suited to SSF. It is concluded that discrete particle simulations provide valuable detailed knowledge about particle transport processes, and this may help to understand and optimize related heat and mass transfer processes in SSF.     

Development of a novel disposable filter bag for separation of biomolecules with functionalized magnetic particles

The integration of disposable magnetic filters in combination with functionalized magnetic particles represents a fast and cost‐effective alternative for enzyme purification in comparison to solid/liquid separation by means of centrifugation followed by chromatographic purification. The main advantage of the particle‐based process is the solid/solid/liquid separation in one step combined with disposable equipment. Furthermore this combination provides the possibility to also process biocatalytic reactions in cell‐containing media into disposable equipment with preimmobilized enzymes onto the magnetic particles. The focus of the presented study is on the design and performance of a disposable filtration unit consisting of a plastic bag with an inlet and outlet and a stainless steel filter matrix. During magnetic separation, the magnetic particles selectively retard at the filter matrix due to the magnetic force, which counteracts the drag force. It was found that the length of a lengthwise aligned filter matrix should be longer than the magnetic pole surfaces in fluid flow direction. Hereby, a filtration capacity of 5.6 g magnetic particles was measured with a loss of below 0.5%. Introducing a two‐phase flow optimizes the cleaning of the bag after a magnetic filtration. The procedure offered a high cleaning efficiency. Herewith, the cleaned filter unit could be discarded with minimum losses of product and magnet particles.     

Ultrasound-assisted hydrolysis and acidogenesis of solid organic wastes in a rotational drum fermentation system

The hydrolysis and acidogenesis of solid organic wastes in a rotational drum fermentation system (RDFS) were improved by direct ultrasonic irradiation (DUSI) and a modified ultrasonic treatment (MUST) composed of dilution, ultrasonic irradiation, and filtration. The effect of DUSI on VA desorption from particle surfaces was estimated. DUSI delivered few distinctions from the broth characteristics, but elevated pH and VS degradation rate (53% higher than the control) in the subsequent acidogenesis. The results demonstrated that DUSI could dislodge VA from particle surfaces and disrupt large-size particles by hydro-mechanical shear force. To improve VA desorption and removal, a MUST process was constructed. The influences of MUST on the characteristics of the fermentation broth and the subsequent acidogenic performance were investigated. MUST raise the broth pH level from 5.1 to 5.5 and remarkably decreased VA concentration from 11.0 to 3.5g/L. At the end of the subsequent acidogenesis, VA increasing ratios, VS degradation ratios, and surface based hydrolysis constants of the fermentors with the control broth (CF) and the treated broth (MUSTF) were 166.7% and 732.0%, 17.0% and 26.7%, and 16.9% and 26.8x10(-6)kgm(-2)d(-1), respectively. With the assistance of MUST, a considerably improved acidogenic performance of solid organic wastes was accomplished in terms of VA production, VS degradation, and particle hydrolysis.     

Recycling of wood chips and wheat dregs for sludge processing

A Buchner filtration study was conducted to investigate the effect on sludge dewatering of adding organic waste solids (wood chips or wheat dregs) to sludge after chemical preconditioning (with ferric chloride or alum). Increasing the dose of wood chips or wheat dregs enhanced sludge filtration performance and increased the energy content of the filter cake, but did not consistently increase the total filtrate removed. The additional filtrate removal was found to balance the inert solids load only when the chemical preconditioner used did not result in sufficient coagulation of the sludge and the skeleton builder dose was low (< or = 90%). Accordingly, various dose ranges of wood chips and wheat dregs are suggested for different sludge management schemes.     

A dense cell retention culture system using stirred ceramic membrane reactor

A novel reactor design incorporating porous ceramic tubes into a stirred jar fermentor was developed. The stirred ceramic membrane reactor has two ceramic tubular membrane units inside the vessel and maintains high filtration flux by alternating use for filtering and recovering from clogging. Each filter unit was linked for both extraction of culture broth and gas sparging. High permeability was maintained for long periods by applying the periodical control between filtering and air sparging during the stirred retention culture of Saccharomyces cerevisiae. The ceramic filter aeration system increased the k(L)a to about five times that of ordinary gas sparing. Using the automatic feeding and filtering system, cell mass concentration reached 207 g/L in a short time, while it was 64 g/L in a fed-batch culture. More than 99% of the growing cells were retained in the fermentor by the filtering culture. Both yield and productivity of cells were also increased by controlling the feeding of fresh medium and filtering the supernatant of the dense cells culture. (c) 1994 John Wiley & Sons, Inc.     

The processing of a plasmid-based gene from E. Coli. Primary recovery by filtration

We describe the primary recovery of plasmid DNA from alkaline lysis mixtures using a nutsche filter operated under pressure. Six different filter cloths constructed of polypropylene, polyester and stainless steel were tested, with pore sizes ranging from 5–160?μm. Both pore size and the material of the filter membranes employed in filtration experiments exerted considerable impact on the purity and yield of the plasmid DNA. The greatest degree of solids extrusion, shearing of chromosomal DNA and subsequent contamination of the filtrate was observed with the 160?μm polyester filter. The best compromise was obtained with a 5?μm polypropylene cloth. For an alkaline lysis mixture containing 101?g wet weight solids per litre, filtration through this cloth proceeded at an average rate of 22.5?cm?h^?1. Virtually complete removal of solids (99.4%) and protein (96.8%) was achieved, with a 8.2-fold purification of plasmid DNA at the expense of a 33% loss in yield. The filtration performance of this membrane was further modified by precoating with diatomaceous earths of different permeabilities (0.07–1.2?darcies). The finest filter aid resulted in very pure plasmid DNA (65%), complete suspended solids removal and ?1), and some losses of plasmid DNA, due to adsorption on to the diatomaceous earth, were also observed (5.7%).     

Cryptosporidium and giardia recoveries in natural waters by using environmental protection agency method 1623

Relatively few studies have examined recoveries from source waters by using Environmental Protection Agency method 1623 with organism spike doses that are environmentally realistic and at turbidity levels commonly found in surface waters. In this study, we evaluated the filtration capacities and recovery efficiencies of the Gelman Envirochek (standard filter) and the Gelman Envirochek high-volume (HV) sampling capsules under environmental conditions. We also examined the performance of method 1623 under ambient conditions with matrix spike experiments using 10 organisms/liter. Under turbid conditions, the HV capsule filtered approximately twice the volume filtered by the standard filter, but neither could filter 10 liters without clogging. In low-turbidity waters, oocyst, but not cyst, recoveries were significantly higher when the HV capsule was used. In turbid waters, organism recoveries were lower than those in nonturbid waters and were not significantly different for the different filters. When the HV capsule was used, Cryptosporidium recoveries ranged from 36 to 75%, and Giardia recoveries ranged from 0.5 to 53%. For both organisms, recoveries varied significantly by site. Turbidity could explain variation in Giardia recoveries (r(2) = 0.80) but not variation in Cryptosporidium recoveries (r(2) = 0.16). The inconsistent recoveries across sites suggested that the background matrix of the ambient water affected recovery by method 1623. A control sample collected at the height of the winter rainy season detected one organism, highlighting the difficulty of using this method to accurately measure pathogen abundance under natural conditions. Our findings support the use of the HV filter under field conditions but suggest that designing a cost-effective and statistically valid monitoring program to evaluate sources and loads of protozoan pathogens may be difficult.