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Abstract A methodology for calculating aerosol filtration efficiency using non-woven filters with polydispersity distribution of fibre diameters was formulated. In order to verify the results of the calculations experimentally, filters made of polypropylene non-woven fabric were used to filter solid (soot) and liquid (oil) aerosols and their mixtures with different concentrations. In order to increase the accuracy of the calculations, the division of the diameter distribution into several (1–100) ranges of values was considered. The influence of the number of these intervals for theoretical and empirical equations available in the literature was investigated. This effect was found to be significant, and replacing one diameter value representing all the fibres in the filter with twenty diameter ranges, each representing only a fraction of the total fibres, is sufficient to minimize the error due to the underrepresentation of the actual fibre distribution in the filter. Calculation of the mean particle size after the filter was performed using a set of theoretical and empirical equations. The calculations take into account the change in packing density, flow velocity and fibre diameter over time as a result of filling the filter with particles deposited on it. The obtained results were compared with the measurement results. It has been found that such changes in the monofilament performance model are insufficient to properly describe the effects inside the filter.

Abstract The dynamics of filtration efficiency and pressure drop during the simultaneous filtration of soot and oil aerosols on single- and multi-layer filters were investigated, and the determined filtration efficiency was compared with the theoretical efficiency obtained via the classical filtration theory. Additionally, the influence of liquid-phase aerosols on the morphology of the formed deposits was investigated. It was concluded that the addition of oil aerosols decreased the filtration efficiency and lowered the pressure drop increase rate for multi-layer filters. Additionally, for the filtration of aerosols containing soot and high oil concentrations, once maximum filtration efficiency was reached, an efficiency decrease occurred. The system imperfection factor was proposed as a mean to predict the efficiency of multi-layer filters. The modified version of the single fibre efficiency method was used to calculate filter mass change with reasonable accuracy.

The flow of air and aerosol particles through the filtering half masks material depends on the structure porosity. It is very difficult to determine the behaviour of the filtering material during the process of extraction and retention of aerosols. The samples of five filtering half mask models were used in this investigation. Dynamics of the aerosol filtration through the filtering materials was tested using a method for testing the leakage of aerosol particles through the filtering material and a method for testing the inhalation resistance of filtering material, both specified in the SRPS EN 149:2013. Recording of the structural changes in the samples of the tested materials was carried out by the technique of scanning electron microscopy. The experiments showed a deviation of the results in relation to the theory of filtration the finely dispersed submicron sized particles. It was concluded that the aerosol leakage through the filtering half masks and their resistance to aerosol flow change depend on the aerosol flow rates and the on filtration process duration, as a direct consequence of the newly-made changes in the structure of the filtering material and due to reversibility effect between the filtration process and the changes in the filtering material. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34034 and Grant no. III45019]

Various modifications are utilized to improve the oil mist separation efficiency of non-woven filters. Our previous work proposed an oleophilisation method involving coating polypropylene filter fibres with porous organosilica aerogel based on methyltrimetoxysilane (MTMS). The filters with fibers with collector area enhanced by this modification exhibited even three times higher initial separation efficiency for oil mists than the native polymer filters. In order to determine the effect of the amount of aerogel layer deposited on polypropylene fibers it is required to investigate the dynamics of filtration of these filters modified with the sol-gel technique over the whole time of use of the filters. This article describes the aerogel deposition influence on the total efficiency of filters over time, efficiency changes for the most penetrating droplets (MPPS), the evolution of pressure drop and oil transport across the material. The results show that the thicker aerogel layer on fibres results in higher initial separation efficiency and pressure drop, simultaneously elongating an initial and transitional loading stage. Filter performance in steady-state seems unaffected by the amount of deposited aerogel. Also, modification with aerogel makes the filter fibres more oleophilic, which translates into changes in filter behaviour described via Jump&Channel theory. • Aerogel modification changes filter characteristics from non-wettable to wettable. • Initial separation efficiency and pressure drop increase with thickness of aerogel layer on fibres. • Thicker aerogel layer results in longer initial and transitional stages of loading. • Thickness of aerogel structure does not affect separation efficiency in steady-state. • Oil transfer evolution across the material is described via Jump&Channel theory. [ABSTRACT FROM AUTHOR]

Abstract: Conventional MBR has been mostly based on floc sludge and the use of costly microfiltration membranes. Here, a novel aerobic granule (AG)-mesh filter MBR (MMBR) process was developed for cost-effective wastewater treatment. During 32-day continuous operation, a predominance of granules was maintained in the system, and good filtration performance was achieved at a low trans-membrane pressure (TMP) of below 0.025m. The granules showed a lower fouling propensity than sludge flocs, attributed to the formation of more porous biocake layer at mesh surface. A low-flux and low-TMP filtration favored a stable system operation. In addition, the reactor had high pollutant removal efficiencies, with a 91.4% chemical oxygen demand removal, 95.7% removal, and a low effluent turbidity of 4.1NTU at the stable stage. This AG-MMBR process offers a promising technology for low-cost and efficient treatment of wastewaters. [Copyright &y& Elsevier]

Evolution of incipient nephropathy in type 2 diabetes mellitus. Background. We examined the course of glomerular injury in 12 Pima Indians with long-standing (>8 years) type 2 diabetes mellitus, normal serum creatinine, and microalbuminuria. They were compared with a group of 10 Pima Indians in Arizona with new-onset (<5 years) type 2 diabetes, normal renal function, and normoalbuminuria (<30 mg albumin/g creatinine on random urine specimens). Methods. A combination of physiological and morphological techniques was used to evaluate glomerular function and structure serially on two occasions separated by a 48-month interval. Clearances of iothalamate and p-aminohippuric acid were used to determine glomerular filtration rate (GFR) and renal plasma flow, respectively. Afferent oncotic pressure was determined by membrane osmometry. The single nephron ultrafiltration coefficient (Kf) was determined by morphometric analysis of glomeruli and mathematical modeling. Results. The urinary albumin-to-creatinine ratio (median + range) increased from 84 (28 to 415) to 260 (31 to 2232) mg/g between the two examinations (P = 0.01), and 6 of 12 patients advanced from incipient (ratio = 30 to 299 mg/g) to overt nephropathy (≥300 mg/g). A 17% decline in GFR between the two examinations from 186 ± 41 to 155 ± 50 mL/min (mean ± SD; P = 0.06) was accompanied by a 17% decline in renal plasma flow (P = 0.003) and a 6% increase in plasma oncotic pressure (P = 0.02). Computed glomerular hydraulic permeability was depressed by 13% below control values at both examinations, a result of a widened basement membrane and a reduction in frequency of epithelial filtration slits. The filtration surface area declined significantly, however, from 6.96 ± 2.53 to 5.51 ± 1.62 × 105 mm2 (P = 0.01), a change that was accompanied by a significant decline in the number of mesangial cells (P = 0.001), endothelial cells (P = 0.038), and... [ABSTRACT FROM AUTHOR]

• Presence of water droplets in gas strongly influences filtration of nanoparticles. • Less efficiency and higher pressure drop during filtration in presence of droplets. • Change of filtration deposits caused by water as a reason of observed changes. • Mass trapped in filter layers depends mostly on their position, not characteristics. The dynamics of filtration efficiency during graphite nanoparticles aerosol filtration on fibrous filters was investigated. The influence of water droplets in feed gas on filtration efficiency, pressure drop as well as the form and shape of filtration deposits collected on filter was examined. Moreover, the mass distribution of collected deposits in individual layers in the case of multilayer filters was examined. We have observed that during the filtration of graphite aerosol in the presence of water droplets the observed pressure drop is significantly greater than during the filtration of sole graphite aerosol. On the other hand, the filtration efficiency is decreased in the presence of water droplets. During the filtration in multilayer filters we observed that the mass of particles deposited in upstream layer is greater than that in downstream, independently of the structure of both layers. This effect is also more significant in the presence of water droplets in feed gas. [ABSTRACT FROM AUTHOR]