An Assessment on Average Pressure Drop and Dust-Holding Capacity of Hollow-Fiber Membranes in Air Filtration.

In this work, we tried to analyze dust loading behavior of polypropylene hollow fiber membranes using average pressure drop models. Hollow fiber membranes varying in fiber diameter were loaded with a standardized test dust to simulate particle-polluted air. We measured pressure drop development of the membranes at different flowrates and dust concentrations, and, after each experiment, the dust deposited on the membrane fibers was weighed to obtain dust holding capacity (DHC). The obtained experimental data was analyzed using various average pressure drop models and compared with average pressure drop obtained from pressure drop/dust load dependence using a curve fit. Exponential and polynomial fitting was used and compared. Pressure drop in relation to the dust load followed different trends depending on the experimental conditions and inner fiber diameter. At higher flowrate, the dependence was polynomial no matter what the fiber diameter. However, with higher fiber diameter at lower permeate velocities, the dependence was close to exponential curve and followed similar trends as observed in planar filter media. Dust-holding capacity of the membranes depended on the experimental conditions and was up to 21.4 g. However, higher dust holding capacity was impossible to reach no matter the experiment duration due to self-cleaning ability of the tested membranes.

Numerical Comparison of Prediction Models for Aerosol Filtration Efficiency Applied on a Hollow-Fiber Membrane Pore Structure.

Hollow-fiber membranes (HFMs) have been widely applied to many liquid treatment applications such as wastewater treatment, membrane contactors/bioreactors and membrane distillation. Despite the fact that HFMs are widely used for gas separation from gas mixtures, their use for mechanical filtration of aerosols is very scarce. In this work, we compared mathematical models developed for the prediction of air filtration efficiency by applying them on the structural parameters of polypropylene HFMs. These membranes are characteristic of pore diameters of about 90 nm and have high solidity, thus providing high potential for nanoparticle removal from air. A single fiber/collector and capillary pore approach was chosen to compare between models developed for fibrous filters and capillary-pore membranes (Nuclepore filters) based on three main mechanisms occurring in aerosol filtration (inertial impaction, interception and diffusion). The collection efficiency due to individual mechanisms differs significantly. The differences are caused by the parameters for which the individual models were developed, i.e., given values of governing dimensionless numbers (Reynolds, Stokes and Peclet number) and also given values of filter porosity and filter fiber diameter. Some models can be used to predict the efficiency of HFMs based on assumptions depending on the conditions and exact membrane parameters.

Levels and Health Risk Assessment of PM10 Aerosol in Brno, Czech Republic.

OBJECTIVE: The main effort of this work was to evaluate the situation of the atmosphere in selected regions of Brno during the years 2009-2013 and to estimate health risks which might come up due to the increased concentrations of airborne particulate matter. METHODS: PM10 samples were collected in four areas varying in degree of automobile traffic using automatic and gravimetric sampling methods. PM10 concentrations were assessed using Spearman's rank correlation coefficient. Health risks were estimated based on calculation of relative risks and population for four health endpoints. The selected health outcomes were premature mortality, cardiovascular disease, respiratory disease, and chronic bronchitis. RESULTS: The highest PM10 concentrations were measured in two regions with high traffic loads T1, T2 and background region B2. The values were 34.33 ± 11.52 µg·m-3 in 2010, 34.87 ± 12.03 µg·m-3 in 2013 and 34.52 ± 8.81 µg·m-3 in 2009, respectively. The highest correlation was between T1 and T2 having Spearman's correlation coefficient 0.888 followed by T1-B1 pair with coefficient 0.886. For all health outcomes, the highest health effect of PM (E) was determined for T2 site in 2010 which was 48 ± 14, 49 ± 21, 44 ± 19 and 24 ± 10 for premature mortality, cardiovascular disease, respiratory disease, and chronic bronchitis, respectively. CONCLUSION: The concentrations are highly correlated, especially in traffic regions. The annual concentrations did not exceed the legislation limit but 24-hours limit was exceeded more than two times in several cases. The highest number of cases with a given health outcome was estimated in traffic regions especially for cardiovascular disease and premature mortality.

Levels, sources, and health risk assessment of polycyclic aromatic hydrocarbons in Brno, Czech Republic: a 5-year study.

This work aimed to determine the seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in airborne PM10 at two background sites (Masná-MS, Lísen-LN) in Brno over a 5-year period (2009-2013). Samples were collected on quartz filters using a low-volume sampler by continual filtration. Concentrations of PAHs in collected PM10 samples were determined using a gas chromatography with a mass spectrometer as a detector. A different number of PAHs were determined to be at each site, i.e., 11 PAHs at the MS site and six PAHs at the LN site, and similarities between them were identified using non-parametric analysis of variance. Potential sources were identified using principal component analysis (PCA) and PAHs diagnostic ratios. The work also focused on health risk assessment. This was estimated using toxic equivalent factors to calculate individual lifetime cancer risk, which quantifies risk of exposure to PAHs for specific age groups. The average 11-PAH concentrations in M|S site annually ranged from 19.28 ± 19.02 ng m-3 (2011) to 40.37 ± 21.35 ng m-3 (2013). With regard to the LN site, the average six-PAH concentrations annually ranged from 3.64 ± 3.87 ng m-3 (2009) and 5.27 ± 6.19 ng m-3 (2012). PCA and diagnostic ratios indicate the main sources to be traffic emissions and coal combustion. Health risk assessment showed carcinogenic risk under limit value in all cases.