Filter Clogging Research Articles

Enhanced nano-aerosol loading performance of multilayer PVDF nanofiber electret filters

Aerosol loading behavior of PVDF nanofiber electret filters using neutrally charged nano- and submicron aerosols was investigated experimentally for the first time. The loading behavior include variations of filtration efficiency and pressure drop and distribution of deposited aerosols in the filters all having the same fiber basis weight (3.060 gsm). Through the filtration efficiency variations of uncharged/charged, single-/multi-layer filters with aerosol loading, it was observed that mechanical PVDF filters had continuously increasing filtration efficiency, while PVDF electret filters had initially decreasing and subsequently increasing filtration efficiency until reaching 100% due to diminishing electrostatic effect and enhancing mechanical effect.By combining the pressure drop evolution of different filters during aerosol loading and detailed SEM images of the loaded filters, we have demonstrated that multilayer PVDF filters, especially the electret ones, could significantly slow down the pace of filter clogging (skin effect) and increase significantly the aerosol holding capacity during depth filtration. Generally, the multilayer nanofiber filters received the most aerosol deposit during depth filtration, whereas the single-layer nanofiber filters with the same basis weight of fibers received the most deposit during cake filtration. The multilayer nanofiber filters had approximately 70% aerosol deposit in the filter during depth filtration fully utilizing the full filter thickness, especially for the electret filters that had charged fibers, and only 30% deposit in the cake. On the contrary, the single-layer uncharged/charged nanofiber filters were exactly the reverse due to persistency of the skin effect with only 30% deposit in the filter mostly located in the upstream layer, yet 70% deposit in the cake. During depth filtration, the pressure drop per added mass deposit for the multilayer electret filter was very low at 11 Pa gsm−1, which was at least twice below any other nanofiber filters. This was all attributed to the uniform capture of aerosols by electrostatic effect across the entire filter depth from the upstream to downstream layers of the multilayer electret filter. The above conclusion was confirmed by the detailed SEM images taken across the different filter layers for the multilayer filter configuration. The 4-layer electret nanofiber filter with a 3.060-gsm basis weight has 4 times more aerosol holding capacity than the single uncharged/charged nanofiber filter with the same fiber basis weight in depth filtration. Based on the standpoint of highest efficiency and capacity with maximum pressure drop 800 Pa imposed on the filtration operation, the 4-layer nanofiber electret was the best among all 4 filters. It had 52% more aerosol holding capacity than the single layer uncharged nanofiber filter and 38% more capacity than the charged single-layer and the uncharged multilayer nanofiber filters. The multilayer PVDF electret filters have excellent filtration performance for long-term aerosol filtration and also great potential applications in the fields of personal health care and environmental protection.

Undulating Multislit Impactor in Ultrahigh-Volume Aerosol Sampler to Reduce Filter Clogging

AbstractUltrahigh-volume samplers with a flow rate of approximately 500 m3/h are widely used for atmospheric radionuclide monitoring. These samplers are often shut down during heavy particulate po...

Effects of filtration methods and water volume on the quantification of brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) eDNA concentrations via droplet digital PCR

AbstractThe quantification of the abundance of aquatic organisms via the use of environmental DNA (eDNA) molecules present in water is potentially a useful tool for efficient and noninvasive population monitoring. However, questions remain about the reliability of molecular methods. Among the factors that can hamper the reliability of the eDNA quantification, we investigated the influence of five filtration methods (filter pore size, filter type) and filtered water volume (1 and 2 L) on the total eDNA and the fish eDNA concentrations of two species, brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) from tanks with known number of individuals and biomass. We applied a droplet digital PCR (ddPCR) approach to DNA extracted from water samples collected from two cultivation tanks (each of them containing one of the targeted species). Results showed that the quantification of fish eDNA concentrations of both species varies with filtration methods. More specifically, the 0.45‐µm Sterivex enclosed filters were identified to recover the highest eDNA concentrations. Difficulties to filter 2 L water samples were present for small pore size filters (≤0.45 µm) and likely caused by filter clogging. To overcome issues related to filter clogging, common in studies aiming to quantify fish eDNA molecules from water samples, we recommend a procedure involving filtration of multiple 1 L water samples with 0.45‐µm enclosed filters, to recover both high quality and high concentrations of eDNA from targeted species, and subsequent processing of independent DNA extracts with the ddPCR method.

Preuse/Poststerilization Integrity Testing (PUPSIT): To Do or Not to Do?

In manufacture of heat labile sterile drug products, the final step involves filtration through sterilizing grade filters. It is the drug manufacturer's responsibility to check whether an integral filter has been used. One method used widely to check the integrity of a filter is the bubble point test. To confirm that the filter used is integral, the postuse integrity test is made obligatory by regulatory bodies. However, preuse/poststerilization integrity testing (PUPSIT) of filters remains debatable for the risks associated in its execution. Although PUPSIT is recommended by regulatory bodies, it poses a risk of compromising downstream sterility and involves high costs to mitigate such risks. This study highlights the impact of filter clogging on bubble point values with the consequent possibility of a nonintegral filter passing postuse integrity testing. The results clearly show an increase in postuse bubble point values, which can camouflage a possible flaw in sterilizing filters. The fluid streams 20% dextrose, 0.001% bentonite, paclitaxel, and 0.05% sodium hyaluronate were selected based not only on the commonality of their clogging propensity but also on the different nature of streams that influence the clogging of sterilizing filters. Paclitaxel is an injectable for oncotherapy, and 0.05% sodium hyaluronate is an ophthalmic. The study was conducted with 0.2 μm sterilizing filters from four different manufacturers. It was observed that some fluid streams show a significant increase in the postuse bubble point test values over the preuse bubble point values. This establishes the necessity of performing PUPSIT in certain cases based on the postfiltration shift in bubble point values. As part of the filter validation studies with specific drug products, additional testing should be carried out to establish the need for PUPSIT on a case-by-case basis.

A new air-washing method to clean fabric filters clogged with submicron fume particles: A pilot-scale study

This study investigates a new air-washing cleaning system that directly injects compressed air on the filter surface for filter regeneration in a fabric filter (FF) dust collector. A pilot-scale FF is designed to test the new system and to compare it with the conventional pulse-jet cleaning system with regard to filter clogging by fume particles. A pleated filter with a filtration area of 2.4 m2 is installed in the FF and a thermal steel spraying gun is used to supply the fume particles. Pressure drop and particle emission concentration are monitored to examine the effect of the new system on filter regeneration and collection efficiency. The results show that the air-washing cleaning is effective for filter regeneration, as it allows the FF to operate stably for a long time, whereas the pulse-jet cleaning fails to achieve filter regeneration, resulting in a continuously increasing pressure drop. In addition, air-washing cleaning shows better performance on collection efficiency than the pulse-jet cleaning method, as it reduces the outlet particulate matter concentration to less than half that of the pulse-jet cleaning.

Determination of the upper limit of monoglyceride content in biodiesel for B30 implementation based on the measurement of the precipitate in a Biodiesel–Petrodiesel fuel blend (BXX)

Biodiesel, in the form of a blended fuel (BXX) with 20%-vol biodiesel (B20), has been on sale on the Indonesian market since early 2016. There is a plan to increase its percentage by up to 30% by 2020, as stated in the biodiesel mandatory phase implementation report. One of the important parameters in biodiesel quality for the implementation of higher biodiesel percentage is monoglyceride content. Monoglyceride presence in biodiesel is caused by the incomplete conversion of raw material oils during the transesterification process, with alcohol, and it remains in the biodiesel product. The presence of monoglyceride in BXX fuel, especially at low-temperature conditions, can cause the formation of a precipitate that accelerates fuel filter clogging. The monoglyceride impurities, even in very low amounts, can trigger the formation of a precipitate. The amount of precipitate is an important factor that can affect the time taken before the fuel filter becomes blocked. The determination of the newly proposed upper limit of monoglyceride content parameter in biodiesel standard is necessary for B30 implementation so the potential amount of monoglyceride precipitate can be anticipated. The limit was proposed to be determined by benchmarking the amount of precipitate formed in B20 or B10 at various temperature conditions. The research was carried out by applying a modified cold soak filtration test method of ASTM D7501 for the precipitation test. Monopalmitin was added to biodiesel with low monoglyceride content to vary monoglyceride content so that each sample had approximate monoglyceride contents of 0.17%, 0.2%, 0.4%, 0.6% and 0.8%. Each biodiesel sample was then blended with petroleum diesel fuel to produce B10, B20 and B30. Each 100 ml sample was separately soaked in the cooling chamber at constant temperature conditions of 15 °C, 20 °C and 25 °C and at a room temperature condition for 21 days. Each sample was then filtered, washed with petro-ether, vacuum-dried and weighed for a constant amount of precipitate retained on the filter. The proposed upper limits of monoglyceride content in biodiesel for B30 with respect to the same amount of precipitate at each corresponding temperature condition in B20 and B10 were found to be 0.62% and 0.50%, respectively. However, with respect to the same amount of precipitate at room temperature in B20, the proposed upper limit of monoglyceride content in biodiesel for B30 was found to be in the range of 0.40–0.62%, while in the range of 0.33–0.51% for B10. From these results, the upper limit of monoglyceride content in biodiesel for B30 implementation should be lower than the current standard limit to achieve the same quality as biodiesel for B20 use.

Evaluation of continuous flow centrifugation as an alternative technique to sample microplastic from water bodies

The scientific and public interest regarding environmental pollution with microplastic has considerably increased within the last 15 years. Nevertheless, up to now there is no widely applied standard operation procedure for microplastic sampling, resulting in a lack of inter-study comparability. In addition, many studies on microplastic occurrences do not indicate a sound methodological validation of the applied methods and procedures. This study presents an alternative volume-reduced sampling technique to sample the entire load of suspended particulate matter including microplastic particles in natural waters, based on continuous flow centrifugation. For the lab-scale validation of the proposed instrumental setup, six different microplastic types (PE, PET, PS, PVDC, EPS and PP) were used. The particles covered a size range from 1 μm to 1 mm and a density range from 0.94 g mL-1 to 1.63 g mL-1. Recoveries ranged from 95.0% ± 2.3% - 99.1% ± 0.3% for virgin powders and from 96.1% ± 0.6% - 99.4% ± 0.2% (1 SD, n = 2 - 3) for microplastic suspended in river water for 40 days. Gravimetric and microscopic analysis of the effluent indicates efficient removal of microplastic from the suspensions. Static light scattering analysis of the microplastic suspensions prior to and after centrifugation confirmed that no change of the particle size distribution has occurred – neither through aggregation nor through size-discrimination during centrifugation. Moreover, the system was tested in the field and used twice to sample suspended particulate matter from the Elbe estuary directly on site. Based on these first lab-scale experiments, continuous flow centrifugation proves a promising technique bearing potential to alleviate drawbacks such as contamination, filter clogging and particle size-discrimination of commonly used volume-reduced microplastic sampling approaches.

A survey of microbial contamination in aviation fuel from aircraft fuel tanks.

Microbial contamination poses a great threat to aviation system security through mechanisms such as microbiologically influenced corrosion (MIC), fuel filter clogging, and fuel deterioration. In this study, a survey of microbial contamination in aviation fuel obtained from aircraft fuel tanks was performed to test the relationship between microbial contamination and aircraft service life. The contaminating microorganisms were counted, isolated, identified, and subjected to preliminary characterization. A low risk of microbial contamination in the selected samples was confirmed, and there was no significant difference in the counts between culturable bacteria and fungi (p > 0.05). Phylogenetic analysis tree indicated that the diversity of culturable microorganisms was rather low, with 17 bacterial isolates belonging to 13 genera and 12 fungal isolates belonging to 5 genera. No yeast was isolated. The growth characteristics of these isolates indicated that the aircraft fuel tanks harbored various microorganisms that were able to utilize the aviation fuel as a source of carbon and energy. Meanwhile, some isolates caused emulsification and produced acid. The conclusions of this study were that various hazardous microorganisms can root in aircraft aviation fuel tanks. There was no relationship between microbial contamination and aircraft service life (p > 0.05), and continuous good maintenance suppressed microbial proliferation.

The impact of biodegradable carbon sources on microbial clogging of vertical up-flow sand filters treating inorganic nitrogen wastewater.

The addition of biodegradable carbon sources to sand filters can enhance microbial activity but may lead to substrate clogging, a major operational problem. In laboratory-scale soil columns emulating vertical up-flow filters, the clogging effect of two readily biodegradable organic substrates-sucrose as a sugar source and ethanol as an alcohol source-were examined with coarse sand as the substrate medium. Wastewater without the addition of supplemental organics and a 'control' treated with tap water were monitored as references. Changes in saturated hydraulic conductivity were measured for all treatments over time. Other parameters that can influence the clogging rate, including temperature, dissolved oxygen, chemical oxygen demand, protein, and polysaccharides, were measured in the influent and effluent wastewater on a weekly basis. At the end of the clogging experiment, the main layer of each filter bed was separated into three sections and saturated hydraulic conductivity, organic matter content, and protein and polysaccharide concentrations were measured in each section. The rate of clogging development in the columns depended on treatment, with ethanol-treated cores clogging more quickly than sucrose-treated cores. Wastewater-treated cores took far longer to clog and the tap water control did not clog, but the saturated hydraulic conductivity declined by 60% over a year. Saturated hydraulic conductivity within the treated cores declined far less than the calculated decline in saturated hydraulic conductivities for the entire cores at the end of the experiment, indicating that clogging in the vicinity of the inlet plate by microbial mats was a major factor influencing the reduction in flow through the columns. To reduce bio-clogging in inlet filters, it may be advantageous to inject organic amendments directly into the bed, rather than pass them through the filters, as is usually the case.

Rapid Clogging of High-Efficiency Particulate Air Filters During In-Cell Solvent Fires at Reprocessing Facilities

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. Moreover, an analysis of the aerosol revealed an increase in unburned solvent content and aerosol particle size generated during the rapid clogging. As such, the rapid clogging may be caused by the unburned solvent release or interactions between the soot and unburned solvent vapor. Overall, this work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.

Microfluidic single valve oscillator for blood plasma filtration

Microfluidic chips analogous to electronic circuits have potential to significantly reduce the reliance of dynamic off-chip controllers for parallel, multiple biochemical fluidic processing. However, even an oscillator for timing reference and biochemical waveform synthesis requires the interaction of multiple on-chip components, substantially increasing formational complexity and internal pressure drop of the total chip. Here, we present a constant flow-driven oscillator consisting of a single microvalve. Without the interaction of other cascaded on-chip components, the microvalve periodically opens and closes, thereby converting the constant inflow into pulsatile outflows. The adjustment of modular mechanical membranes enabled the control of the oscillation periods in the range of 0.4 s–30 min, with duty cycles of 0.03–0.8. We also demonstrate the ability of the microvalve oscillator in performing pulsatile blood plasma filtrations. The device could continuously filter plasma, without being significantly affected by filter clogging by red blood cells, for 1 h. Our microvalve oscillator without any cascaded multiple elements can be used for parallel and multiple biochemical fluidic processing.

A New Hybrid Prognostic Methodology

Methodologies for prognostics usually centre on physics-based or data-driven approaches. Both have advantages and disadvantages, but accurate prediction relies on extensive data being available. For industrial applications, this is very rarely the case, and hence the chosen method’s performance can deteriorate quite markedly from optimal. For this reason, a hybrid methodology, merging physics-based and data-driven approaches, has been developed and is reported here. Most, if not all, hybrid methods apply physics-based and data-driven approaches in different steps of the prognostics process (i.e. state estimation and state forecasting). The presented technique combines both methods in forecasting, and integrates the short-term prediction of a physics-based model with the longer-term projection of a similarity-based data-driven model, to obtain remaining useful life estimation. The proposed hybrid prognostic methodology has been tested on two engineering datasets, one for crack growth and the other for filter clogging. The performance of the presented methodology has been evaluated by comparing remaining useful life estimations obtained from both hybrid and individual prognostic models. The results show that the presented methodology improves accuracy, robustness and applicability, especially in the case of minimal data being available.

Diesel Engine Acoustic Emission Airflow Clogging Diagnostics With Machine Learning

A diesel engine electrical generator set (“gen-set”) was instrumented with in-cylinder indicating sensors as well as acoustic emission microphones near the engine. Air filter clogging was emulated by progressive restriction of the engine's inlet air flow path during which comprehensive engine and acoustic data were collected. Fast Fourier transforms (FFTs) were analyzed on the acoustic data. Dominant FFT peaks were then applied to supervised machine learning neural network analysis with matlab-based tools. The progressive detection of the air path clogging was audibly determined with correlation coefficients greater than 95% on test data sets for various FFT minimum intensity thresholds. Further, unsupervised machine learning self-organizing maps (SOMs) were produced during normal-baseline operation of the engine. The degrading air flow engine sound data were then applied to the normal-baseline operation SOM. The quantization error (QE) of the degraded engine data showed clear statistical differentiation from the normal operation data map. This unsupervised SOM-based approach does not know the engine degradation behavior in advance, yet shows clear promise as a method to monitor and detect changing engine operation. Companion in-cylinder combustion data additionally shows the degrading nature of the engine's combustion with progressive airflow restriction (richer and lower density combustion).

The use of hollow fiber dialysis filters operated in axial flow mode for recovery of microorganisms in large volume water samples with high loadings of particulate matter

Ultrafiltration concentration of microorganisms in large volume water samples containing high levels of particulate matter was evaluated in a proof of concept study. The organisms tested were Bacillus atrophaeus subspecies globigii spores and MS2 bacteriophage. To produce the large volume samples, fresh water sediment of a known particle size was added to 51 l of tap water. Five different concentrations of particulate matter were studied: 0, 50, 100, 150 and 750 mg solids/l. The concentration procedure used a dialysis filter as the ultrafilter configured for axial flow, either with or without recirculation. The target number of organisms spiked was 1 × 105 of either spores or bacteriophage per 51 l. After concentration, the filters were dissected to retrieve the fibers which were then washed using surfactant solution which was then analyzed for the target organisms. Two washes of the filter fibers were carried out sequentially. For axial flow with recirculation, the first wash produced statistically greater recovery of B. globigii spores (26–40% of spike) compared to the second wash (8–13% of spike). Total recovery (the sum of the recoveries for the first and second washes) ranged from 35 to 53%. Recovery increased as the solids level increased from 0 to 150 mg solids/l. Recovery at the 100 and 150 mg solids/L loadings was statistically higher at the P < .05 level than recovery at 0 mg/L solids. At 150 mg solids/L, axial flow without recirculation (dead end) yielded lower recovery than axial flow with recirculation, however the difference was not significant at the P < .05 level. Recovery of B. globigii at 750 mg solids/L averaged 38% using dead end axial flow. The average recovery of MS2 bacteriophage was 45% at a solids concentration of 150 mg/L using axial flow with recirculation. PhiX174 and Phi8 were also studied, however these bacteriophage appeared to be inactivated in the matrix of concentrated wash water. One hundred liters of water containing 750 mg solids/L was concentrated using dead end axial flow, and only minimal problems with filter clogging were observed. Results described herein suggest axial flow ultrafiltration is an effective concentration method for microorganisms in water containing high levels of particulate matter.

Pilot scale recovery of lignin from black liquor and advanced characterization of the final product

Recently, the academic and industrial interest in lignin as a renewable resource for many valuable applications has been on the rise. However, the current biomass separation technologies are focused on obtaining high quality cellulose which can be further processed, e.g., in the paper industry, resulting in a lignin of rather low quality. Moreover, lignin recovery from black liquor is often accompanied with filter clogging and a severe flux decline, limiting the cost-efficiency of its valorization. In this work, the pilot scale recovery of lignin from a black liquor derived from a mild soda pulping process of Miscanthus x giganteus chips is studied with the aim to develop a straightforward procedure that yields a high quality final product. A first pilot scale experiment demonstrated the pH to be crucial for optimal precipitation. Moreover, adding an enzyme mixture containing cellulases, hemicellulases and β-glucosidases, clearly enhanced the flocculation and filterability. Thorough characterization of the obtained lignin showed a native-like structure which can be related to the mild pulping conditions and revealed that the p-coumarates and ferulates were converted to the free acids as a result of the base catalyzed hydrolysis as well as the enzymatic cleavage of the ester linkages leading to the complete removal of the hydrophilic (poly)saccharides. Moreover, this resulted in a slightly more hydrophobic lignin material that was more amenable to flocculation. Building on lab scale experiments aimed at optimization of the process conditions, a second pilot scale experiment was performed resulting in improved precipitation and flocculation by means of acidification, an enzymatic treatment as well as the addition of a flocculant. This allowed for smooth filtration and resulted in a high purity of the isolated lignin.

Improving eDNA yield and inhibitor reduction through increased water volumes and multi-filter isolation techniques

To inform management and conservation decisions, environmental DNA (eDNA) methods are used to detect genetic material shed into the water by imperiled and invasive species. Methodological enhancements are needed to reduce filter clogging, PCR inhibition, and false-negative detections when eDNA is at low concentrations. In the first of three simple experiments, we sought to ameliorate filter clogging from particulates and organic material through a scaled-up, multi-filter protocol. We combined four filters in a 5 mL Phenol-Chloroform-Isoamyl (PCI) procedure to allow for larger volumes of water (~1 L) to be filtered rapidly. Increasing the filtered water volume by four times resulted in 4.4X the yield of target DNA. Next, inhibition from organic material can reduce or block eDNA detections in PCR-based assays. To remove inhibitory compounds retained during eDNA isolation, we tested three methods to chemically strip inhibitors from eDNA molecules. The use of CTAB as a short-term (5–8 day) storage buffer, followed by a PCI isolation, resulted in the highest eDNA yields. Finally, as opposed to a linear relationship among increasing concentrations of filtered genomic eDNA, we observed a sharp change between the lower (70–280 ng) and higher (420–560 ng) amounts. This may be important for effectively precipitating eDNA during protocol testing.

Detection of ESAs in equine urine and blood by SAR-PAGE.

AbstractErythropoiesis‐stimulating agents (ESAs) have been used in horses for doping purposes to increase the performance of these animals in endurance sports. Currently, enzyme‐linked immunosorbent assay (ELISA) and mass spectrometry methods are used to detect ESA abuse in equines. However, the sarcosyl polyacrylamide gel‐electrophoresis (SAR‐PAGE) technique could also be used, since its application in human doping control is well established and has proven to be more sensitive. In this work, the SAR‐PAGE method was used to detect recombinant human erythropoietin (rHuEPO), novel erythropoiesis stimulating protein (NESP), continuous erythropoietin receptor activator (CERA), and fusion protein of erythropoietin with human immunoglobulin heavy chain Fc region (EPO‐Fc) in horse blood and urine. The purification technique for human blood using MAIIA kits worked well for horse samples. The major challenge was horse urine immunopurification, which proved difficult due to filter clogging, but heating and cooling of the horse urine followed by filtration in 30‐kDa molecular weight cut‐off filters solved this problem. The limits of detection (LODs) of 1.3, 1.6, 6.6, and 13.3 pg/mL for rHuEPO, NESP, CERA, and EPO‐Fc, respectively, obtained in spiked urine and 40, 100, 80, and 400 pg/mL for rHuEPO, NESP, CERA, and EPO‐Fc, respectively, acquired in spiked blood are lower than the LODs reported in the literature using liquid chromatography–mass spectrometry (LC–MS) methods. In addition, the presence of ESAs was detected up to 9 days after the administration of microdoses of Hemax (rHuEPO), NESP, and CERA in horse blood and urine. SAR‐PAGE may be implemented in the routine analysis of horse doping control laboratories for screening and confirmation of ESA abuse, mainly due to its high sensitivity for both matrices compared to published mass spectrometric methods.

Efficiency of cleaning and the life cycle of the modernized filter for rough cleaning of diesel fuel

The paper considers the problem of the reliability of the fuel equipment of tractor diesel engines at low temperatures. The main problem of the operation of such engines is the deterioration of fuel pumpability through the fuel lines, waxing and clogging of fine filters. The authors propose a new design of the coarse filter (CF), where the filter element is a filter tape made of nonwoven needle-punched material with variable compression, which has increased filtration efficiency with the possibility of simultaneous heating of the fuel. The advantage of the proposed changes is the use of a standard coarse filter housing. Performance tests are presented. According to the results of operational tests of the upgraded coarse filter, it was found that, unlike the standard element, the mass concentration of contaminants is reduced by about half, and the probability of dropping out particles larger than 30 microns is 90 %. The particle size distribution curves of contaminants after a standard and upgraded filter and a resource characteristic are built. The results of comparative operational tests of filters for pollution are presented. The pressure drop across the filter at the onset of maintenance is estimated, and an increase in scheduled filter replacement is suggested. The degree of compression of the filtering material was determined to exclude the appearance of particles larger than 35 μm after the CF.

Accelerated Sample Preparation for Fast Salmonella Detection in Poultry Products.

Salmonella is the most burdensome foodborne pathogen in the USA and a major causal agent of foodborne outbreaks. Detection of a pathogen such as Salmonella can be achieved within a few hours using commercially available rapid methods, but the sample preparation is time consuming and may require multiple days. We have developed and successfully tested an accelerated sample preparation method based on microfiltration, in some cases preceded by a short enrichment step, for the rapid detection of selected pathogens. The time-frame of the overall process, from sample preparation (i.e., food rinse or homogenate preparation, microbial enrichment, and filtration steps) to detection is 8h or less. While microfiltration has been practiced for 70years, the complex interactions between food substances and filter membrane surfaces have shown that food pretreatment methods need to be developed on a case by case basis for the recovery of bacteria from food homogenates and/or rinses. We have also demonstrated that addition of protease to treat homogenates of different poultry products prior to microfiltration avoids the rapid decrease in flux that otherwise occurs during microfiltration. This protease treatment minimizes filter clogging, so that the microbial concentration, recovery and detection of 1 to 10CFU/g of Salmonella in poultry products is possible in less than 8h.

Using upstream oxidants to minimize surface biofouling and improve hydraulic performance in GAC biofilters

The combination of biological growth and particle loading can adversely affect hydraulic performance in drinking water biofilters. In this study, upstream oxidant addition was used to distribute biologically-derived filter clogging in granular activated carbon (GAC) biofilters. Oxidant penetration was assessed during pilot-scale operation and backwashing of dual media (GAC/sand) and multimedia (GAC/anthracite/sand) biofilters. Influent chlorine (HOCl), monochloramine (NH2Cl), and hydrogen peroxide (H2O2) residuals were optimized to react with the GAC surface in the upper portion of the filter media bed (depth < 0.5 m) to attenuate biomass development. As the oxidant residual was quenched by surface-mediated reaction with the filter media, biomass growth was promoted deeper in the filter bed (depth > 0.5 m). The oxidant-induced effects on biomass and hydraulic performance were monitored through measurements of adenosine triphosphate (ATP) and head loss accumulation at different media depths. Addition of oxidants (e.g., 0.6 mg Cl2/L HOCl) could decrease terminal head loss by 20% in dual media filters and 40% in multimedia filters. These hydraulic benefits were achieved without significantly affecting removal of assimilable organic carbon (AOC), total organic carbon (TOC), turbidity, and particle counts. Oxidant type, residual concentration, media type, media age, and media depth influenced the passage of oxidant residuals and distribution of filter biomass. When oxidants were added during backwashing, oxidant residual was quenched through the bed depth from a combination of reactions with GAC media and biofilm degradation. This attenuation of residual oxidant may prevent the oxidant residual from penetrating the entire bed depth, potentially compromising backwashing objectives.