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Viral filtration is a critical step in the purification of biologics and in the monitoring of microbiological water quality. Viral filters are also essential protection elements against airborne viral particles. The present review first focuses on cellulose-based filter media currently used for size-exclusion and/or adsorptive filtration of viruses from biopharmaceutical and environmental water samples. Data from spiking studies quantifying the viral filtration performance of cellulosic filters are detailed, i.e., first, the virus reduction capacity of regenerated cellulose hollow fiber filters in the manufacturing process of blood products and, second, the efficiency of virus recovery/concentration from water samples by the viradel (virus adsorption–elution) method using charge modified, electropositive cellulosic filters or conventional electronegative cellulose ester microfilters. Viral analysis of field water samples by the viradel technique is also surveyed. This review then describes cellulose-based filter media used in individual protection equipment against airborne viral pathogens, presenting innovative filtration media with virucidal properties. Some pros and cons of cellulosic viral filters and perspectives for cellulose-based materials in viral filtration are underlined in the review.

High efficiency particulate air (HEPA) filters are widely used in various industries to contain airborne contamination. The pressure drop of the filters is a crucial performance parameter when designing a HEPA filter as it is the resistance that the filter offers to the flow of air. Thus, it is critical to find the effect of each configuration and integrate an optimal setup for the filter to avoid high-pressure drops. Set against these backgrounds, this study aims to study the effect of different configurations on the total pressure drop of the filter, and to review how each configuration can affect each other using a commercial software ANSYS Fluent. The different filter media pack configurations and boundary conditions investigated here are including pleat shape (V-shaped and U-shaped), pleat density (1-7 pleat/cm), pleat height (1cm, 1.3cm), and inlet velocity (0.02-0.2 m/s) on the pressure drop of the filter. A two-dimensional geometrical model is developed, and then validated with respect to the data obtained from Lydall M3004-06 property sheet. Upon successful validation exercise, a series of parametric studies is conducted to numerically examine the impact of changing each configuration on the total pressure drop of the filter. Results show that an optimal pleat density is attained where the total pressure drop is minimized, i.e., 3 pleat/cm for V-shaped and 4 pleat/cm for U-shaped for inlet velocity of 0.02 m/s. At a constant inlet velocity, the U-shaped pleat has a lower pressure drop than the V-shaped pleat at low pleat densities, but a higher pressure drop at higher densities. This behaviour can be attributed to the balance between inertial and viscous resistance. Increasing the inlet velocity increases the total pressure drop for all pleat heights and decreases the optimal pleat density. This effect is less pronounced on the V-shaped pleat. Increasing the pleat height for the U-shaped pleat decreases the pressure drop and optimal pleat density but increases pressure drop in the viscous dominated region. Conversely, increasing the pleat height for the V-shaped pleat decreases the pressure drop for all pleat counts and only decreases the optimal pleat density at high velocity.

ABS was the first surfactant used in detergent formulations, but because its molecular structure is branched, it is difficult to decompose biologically, making ABS a toxic compound for the environment. This study aims to remove MBAS surfactant, using a combination of phytoremediation and filtration methods to remove surfactant (MBAS) Chemical Oxygen Demand (COD) from detergent wastewater by optimizing operating factors such as pH, contact time, plant type, and filter media. Water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) were selected as plant species and silica-activated carbon was used as filter media. Water lettuce and hyacinth were grown in a 10-liter reactor with detergent wastewater samples for 6 and 12 days. Filter media are placed in the reactor in use, and aeration is done. The efficiency for reducing COD was 81.73%, and the efficiency for surfactant was 99.42% for each experiment, which was thought to be because of plant adsorption and filtering processes. The water lettuce (Pistia stratiotes) plant had the maximum adsorption capability for all the qualities evaluated, with a surfactant content in the roots of 27543.24 (mg/kg MBAS), compared to the water hyacinth plant, which only absorbed 2597.95 (mg/kg MBAS).

The sand media filter is a crucial component of micro-irrigation filtration systems. Investigating the effects of various factors on filtration performance and the migration patterns of sediment particles within the filter can enhance the healthy operation of sand media filters. This study, based on a sand media filter model, conducts indoor hydraulic experiments, selecting different experimental factors and observation indices for research under varying conditions. Results indicate that filter thickness and raw water concentration are positively correlated with the turbidity of filtered water samples, while changes in filtration rate have no obvious impact on turbidity. When filter thickness is large, particle content differs obviously from other filter thicknesses, and the effect of raw water concentration changes on particle content is similar to that of filter thickness changes. Sediment particle size distribution within the filter layer is primarily concentrated in the upper region. By focusing on the area situated 20 cm below the filter layer surface, the sediment retention rate reached 80% or higher at a depth of 20 cm below the filter layer surface. As the depth of the filter layer increases, the sediment retention characteristics show a decreasing trend for larger particle sizes and an increasing trend for smaller particle sizes. Head loss is positively correlated with filtration rate, raw water concentrations, and filter thickness changes. It is suggested that, when meeting micro-irrigation water quality requirements, the filter material particle size can be appropriately increased to improve filtration efficiency and reduce energy consumption. These research findings are highly significant for sand media filter material selection and working condition design.

Most FFP (Filtering Face Piece) masks are made from nonwoven filter media that are electrostatically charged, resulting in the additional electrostatic capture mechanism of particles. The protective effect of these masks is therefore mainly dependent on the electric field surrounding the charged fibers. Upon prolonged wear, the mask becomes saturated with exhaled air, resulting in humidification on the wearer’s side. However, speaking, coughing, or sneezing also generate droplets, which can deposit on the mask from the person wearing it, as well as from other people. In order to investigate this influence on the filtration efficiency and the existing electric field, an experimental study was carried out. To imitate human breathing, a test setup was constructed using a Sheffield Head with different types of masks. This was followed by the cyclical humidification and drying of the masks through simulated breathing. By observing these phases in detail using sample sections, it was possible to continuously record the water content in the samples, the relative humidity, and the pressure drop (breathing resistance). The results demonstrate that moisture has an impact on the filtration efficiency of the electret FFP masks when worn under real-life conditions and that the initial condition can be restored with sufficient drying time.

Electret filter media are electrostatically charged during the manufacturing process to activate effective electrical separation mechanisms. In order to investigate the influence of humidity on these mechanisms, the electric field, and filtration efficiency, a Direct Numerical Simulation (DNS) study of the aerosol deposition within wetted fibrous nonwoven filter media used in masks was carried out. Initial experimental investigations determined key properties of the filter material, including porosity, fiber diameter, and surface charge density. Using Micro-Computed Tomography (µCT), preferred locations for droplet deposition within the filter were identified. Additional experiments quantified the amount of water absorbed by the filter medium and assessed its impact on the existing electric field. Numerical simulations examined various models with differing porosity and fiber diameter, incorporating different levels of water content to analyze the changes in the electric field, flow velocity, and resulting filtration efficiency. The results provide valuable insights into the significant effects of fiber change on filtration performance, demonstrating the electret filter’s ability to partially compensate for the negative impacts of water.

The current study aimed to investigate the efficiencies and mechanisms of slag filter media for removing phosphorus from synthetic wastewater. The steel slag with high ferric oxides (Fe 2 O 3 ) was subjected for the electric arc furnace (EAF) and selected as the filter media (HFe). The chemical characteristics of HFe were determined using pH, point of zero charge (PZC) and XRF. The phosphorus removal efficiency was studied in a designed vertical steel slag column rock filters in unaerated HFe (UEF) and aerated HFe (AEF) system. The microstructure of HFe was analyzed by FTIR, XRD and SEM-EDX analysis. The results of XRF revealed that ferric oxide (Fe 2 O 3 ) ranged from 26.1 to 38.2%. PZC for Filter HFe was recorded at pH 10.55 ± 0.27. The highest efficiencies were recorded by UEF and AEF systems at pH 3 and pH 5 (89.97 ± 4.02% and 79.95 ± 6.25% at pH 3 and 72.97 ± 8.38% and 66.00 ± 12.85% at pH 5 for UEF and AEF, respectively). These findings indicated that AEF exhibiting higher removal than UEF systems might be due to presence high Fe concentration in AEF which play important role in the phosphorus removal. The main elements available on the surface of HFe included carbon, oxygen, iron, calcium, magnesium, silicon, platinum, sulphur, manganese, titanium and aluminium. The XRD analysis indicated that the precipitation of orthophosphate as calcium and iron-phosphates was the removal mechanism as confirmed using FT-IR analysis. These findings demonstrated the efficiency of HFe in removing of phosphorus from wastewater.

The main aim of this study is to assess the preparation, sintering behavior, and expansion performance of ceramsite filter media (CFM) from dewatered sewage sludge, coal fly ash, and river sediment without using any natural resources. The results showed that the investigated physical properties of lab made CFM met with the China’s industrial standard of CJ/T 299-2008 and the concentration of heavy metals in the lixivium was lower than the threshold of GB 5085.3-2007. During the sintering process, the relationships between ignition loss rate, expansion rate, and sintering temperature could be well described simultaneously by the 3-order polynomial fitting curve, with high correlation coefficient values (R2 > 0.999). The fitting curves of the ignition loss rate and expansion rate had one peak and one valley, respectively, and their cut-off point that is the sintering temperatures were the same (700 °C). The whole sintering process could be divided into two stages. The ignition loss rate was gradually increased in both the stages. At the same time, the expansion rate was decreased in the first stage and then increased in the second stage. The significance of this work is to pursue the concept of sustainable development.

To improve the separation efficiency of the oil/water mixture and simplify the separation process, a superhydrophilic/underwater superoleophobic quartz sand filter media (PR@QS) was prepared by coating potato residue onto the quartz sand surface, and an oil/water mixture separator containing two horizontally placed filter columns and one inlet chamber was proposed. One filter column was filled with the PR@QS, and the other column was filled with the superhydrophobic/superoleophilic quartz sand filter media. The experimental results showed that the separation efficiencies of five kinds of oil/water mixtures (petroleum ether, engine oil, diesel oil, cyclohexane, and methylene chloride) were up to 99.4%. Except for engine oil, the hydraulic conductivities of the other four oils and water are all greater than 3.5 m/h. When the filter layer is invaded by the lyophobic liquid, its filtration performance can be restored by backwashing. In summary, the separator can separate oil/water mixtures continuously and efficiently without filter contamination. Therefore, it has a broad prospect for practical application.

The biofiltration system over organic bed (BFOB) uses organic filter material (OFM) to treat municipal wastewater (MWW). This study evaluated the performance of a BFOB system employing mesquite wood chips (Prosopis) as OFM. It also evaluated the effect of hydraulic loading rates (HLRs) in order to achieve the operational parameters required to remove organic matter, suspended material, and pathogens, thus meeting Mexican and US regulations for reuse in irrigation. Two biofilters (BFs) connected in series were installed; the first one aerated (0.62 m3air m−2h−1) and the second one unaerated. The source of MWW was a treatment plant located in Durango, Mexico. For 200 days, three HLRs (0.54, 1.07, and 1.34 m3m−2d−1) were tested. The maximum HLR at which the system showed a high removal efficiency of pollutants and met regulatory standards for reuse in irrigation was 1.07 m3m−2d−1, achieving removal efficiencies of biochemical oxygen demand (BOD5) 92%, chemical oxygen demand (COD) 78%, total suspended solids (TSS) 95%, and four log units of fecal coliforms. Electrical conductivity in the effluent ensures that it would not cause soil salinity. Therefore, mesquite wood chips can be considered an innovative material suitable as OFM for BFs treating wastewaters.