Search Results (13)

Charged particles have high momentum under high-temperature conditions, which helps to promote their movement towards a dust collector in a magnetic field environment, making it possible to improve the efficiency of the high-temperature wire-plate electrostatic precipitator (ESP) in this environment. A multi-field coupling model was established to numerically simulate PM2.5 dust-removal efficiency in an ESP under different working conditions. Combining the particle swarm optimization (PSO) algorithm with the support vector machine (SVM) model, the PSO-SVM prediction model is presented. Simulated data were used as training data, and PSO-SVM and back-propagation (BP) neural network models were utilized to predict collection efficiency under different working conditions, respectively. The results show that introducing a magnetic field can effectively improve the PM2.5 collection efficiency of wire-plate ESP, and the effect of a magnetic field on the dust-removal efficiency is more obvious at higher temperatures and higher flue gas velocities. When changing the working conditions, the predicted results of the magnetic field effect conform to simulated ones, and the PSO-SVM predicted values have a smaller relative error than those of the BP model, which can better adapt to different working conditions. All of the above conclusions can be utilized as a simple and adequately efficient example of the ESP model for follow-up research. Full article

WESPs (Wet Electrostatic precipitators) are mainly installed in industries and factories where PM (particulate matter) is primarily generated. Such a wet type WESPs exhibits very excellent performance by showing a PM collection efficiency of 97 to 99%, but the PM collection efficiency may decrease rapidly due to a situation in which the dust collector and the discharge electrode is corroded by water. Thus, developing technology to predict efficient PM collection in the design and operation of WESPs is critical. Previous studies have mainly developed machine learning-based models to predict atmospheric PM concentrations using data measured by meteorological agencies. However, the analysis of models for predicting the dust collection efficiency of WESPs installed in factories and industrial facilities is insufficient. In this study, a WESPs was installed, and PM collection experiments were conducted. Nonlinear data such as operating conditions and PM measurements were collected, and ensemble PM collection efficiency prediction models were developed. According to the research results, the random forest model yielded excellent performance, with the best results achieved when the target was PM 7: R2, MAE, and MSE scores of 0.956, 0.747, and 1.748, respectively. Full article

Wet electrostatic precipitators have problems such as uneven water distribution and poor economy in applying ultra-clean particulate matter emissions from coal-fired boilers. Upgrading the droplets in wet dust removal to charged mobile collectors can effectively compensate for these shortcomings. In this paper, the effects of particle sphericity, particle size, and charge on the capture efficiency of a single droplet for capturing micron and submicron particles are qualitatively studied by simulating the process of particle capture by charged droplets in a turbulent flow field. The simulation results show that the trapping efficiency of charged droplets is positively correlated with the sphericity and the amount of charge. The particle size significantly impacts the capture efficiency, and the increase in size increases the capture efficiency, and the capture efficiency of 5.49 μm particles reaches 100%. The effect of particle movement speed on the capture efficiency needs to be considered in combination with particle size. For micron particles, the capture efficiency is close to 100% when the movement speed is 0.3 m/s and 0.5 m/s. For submicron particles, the aggregation morphology is lower at lower speeds. Simple non-spherical particles have greater capture efficiency. Full article

Hybrid electrostatic precipitators consisting of electrostatic precipitation (ESP) and a bag filter are potential devices for ultralow emissions. The ESP captures and charges the particles; subsequently, the charged particles that escape enter the bag filter. The charged particles can cause the electric field of the filter bag to develop, thereby enhancing the filtration efficiency due to the force of the electric field. Experiments based on the coupling-reinforced electrostatic–fabric integrated precipitator system were conducted to investigate the outlet total dust concentration, dust removal efficiency, pressure drop, energy consumption of bag filter, and hybrid electrostatic precipitators with various filter bags. The measured results demonstrate that the removal performance of filter bags with smaller fiber diameters was superior. However, the pressure drop and energy consumption were high due to the increased filtration resistance. Compared to bag filters, hybrid electrostatic precipitators had lower total and grade dust mass concentrations at the outlet, higher total and grade dust removal efficiencies, a minor average pressure drop variation per minute, and lower total energy consumption. Consequently, the quality factor was utilized to comprehensively evaluate the overall performance of dust collectors. The hybrid electrostatic precipitators had a significant greater quality factor; their overall performance was superior to that of bag filters. Overall, a smaller filter bag’s fiber diameter resulted in more effective dust removal capabilities. Hybrid electrostatic precipitators with various filter bags were significantly better than bag filters in terms of dust removal performance, cycle life, and energy consumption. Full article

In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) of the inertial separator and the ESP were evaluated according to brake pad type. In the case of the inertial separator, the BWP collection efficiencies for the low-metallic (LM) and non-asbestos organic (NAO) pads were similar, and the cut-off size at 50% collection efficiency (D50) was 2.2 µm. The ESP was designed without an additional electrostatic charging device because naturally induced electrostatic charging occurred due to the friction between the brake disc and pad. The BWP collection efficiency of the ESP was higher for NAO pad than for LM pad because the BWPs generated from the NAO pad contained a relatively low iron (Fe) component compared to that of the LM pad, thereby generating more frictional electricity. The maximum ESP collection efficiencies of the BWPs generated from the LM and NAO pads were determined to be 60% and 75%, respectively, and the remaining BWPs that were not collected were presumed to be particles that were not frictionally charged. Full article

Chlorine (Cl) released from coal-fired power plants can be harmful to power equipment, the ecological environment and human health. Here, we investigated the Cl releasing characteristics from four coal-fired power plants (CFPPs) in China’s Anhui province based on an ion chromatography analysis of the combustion by-production samples collected from different locations of the power plants. The results showed that Cl content in coals was low (198–367 μg·g⁻¹), which positively correlated with the contents of lead, mercury and total sulfur, but was weakly correlated with the moisture and ash yield in coal. The releasing rate of Cl during coal combustion was highly correlated with temperature and volatile matter, and most Cl is transferred into the flue gas. Dust collector and wet flue gas devices equipped in the CFPPs were robust for removing Cl in the particulate phase, and the fabric filter showed a higher removal efficiency than the electrostatic precipitator. This study can provide theoretical support for Cl pollution control in coal-fired power plants. Full article

Background: Aspergillus section Fumigati is one of the Aspergillus sections more frequently related to respiratory symptoms and by other health outcomes. This study aimed to characterize Aspergillus section Fumigati distribution in eleven firefighter headquarters (FFHs) to obtain an accurate occupational exposure assessment. Methods: A sampling approach protocol was performed using active (impaction method) and passive sampling methods (floor surfaces swabs, electrostatic dust collectors (EDCs), and settled dust). All samples were analysed by culture-based methods and passive sampling was used for molecular detection of Aspergillus section Fumigati. Results: Of all the matrices, the highest counts of Aspergillus sp. were obtained on settled dust filters (3.37% malt extract agar—MEA, 19.09% dichloran glycerol—DG18) followed by cleaning cloths (1.67% MEA; 7.07% DG18). Among the Aspergillus genus, the Fumigati section was predominant in Millipore and EDC samples in MEA (79.77% and 28.57%, respectively), and in swabs and settled dust filters in DG18 (44.76% and 30%, respectively). The Fumigati section was detected more frequently in DG18 (33.01%) compared to MEA (0.33%). The Fumigati section was observed in azole supplemented media (itraconazole and voriconazole) in several passive sampling methods employed and detected by qPCR in almost all passive samples, with EDCs being the matrix with the highest prevalence (n = 61; 67.8%). Conclusion: This study confirms that Aspergillus sp. is widespread and the Fumigati section is present in all FFHs. The presence of fungi potentially resistant to azoles in the FFHs was also observed. Further studies are needed to identify the best corrective and preventive measures to avoid this section contamination in this specific occupational environment. Full article

Sampling campaigns indoors have shown that occupants exposed to contaminated air generally exhibit diverse health outcomes. This study intends to assess the deposition rates of total settleable dust and bioburden in the indoor air of dwellings onto quartz fiber filters and electrostatic dust collectors (EDCs), respectively. EDC extracts were inoculated onto malt extract agar (MEA) and dichloran glycerol (DG18) agar-based media used for fungal contamination characterization, while tryptic soy agar (TSA) was applied for total bacteria assessment, and violet red bile agar (VRBA) for Gram-negative bacteria. Azole-resistance screening and molecular detection by qPCR was also performed. Dust loading rates ranged from 0.111 to 3.52, averaging 0.675 μg cm⁻² day⁻¹. Bacterial counts ranged from undetectable to 16.3 colony-forming units (CFU) m⁻² day⁻¹ and to 2.95 CFU m⁻² day⁻¹ in TSA and VRBA, respectively. Fungal contamination ranged from 1.97 to 35.4 CFU m⁻² day⁻¹ in MEA, and from undetectable to 48.8 CFU m⁻² day⁻¹ in DG18. Penicillium sp. presented the highest prevalence in MEA media (36.2%) and Cladosporium sp. in DG18 (39.2%). It was possible to observe: (a) settleable dust loadings and fungal contamination higher in dwellings with pets; (b) fungal species considered indicators of harmful fungal contamination; (c) Aspergillus section Candidi identified in supplemented media with voriconazole and posaconazole; (d) specific housing typologies and (e) specific housing characteristics influencing the microbial contamination. Full article

The exposure to particles and bioaerosols has been associated with the increase in health effects in children. The objective of this study was to assess the indoor exposure to bioburden in the indoor microenvironments more frequented by children. Air particulate matter (PM) and settled dust were sampled in 33 dwellings and four schools with a medium volume sampler and with a passive method using electrostatic dust collectors (EDC), respectively. Settled dust collected by EDC was analyzed by culture-based methods (including azole resistance profile) and using qPCR. Results showed that the PM2.5 and PM10 concentrations in classrooms (31.15 μg/m³ and 57.83 μg/m³, respectively) were higher than in homes (15.26 μg/m³ and 18.95 μg/m³, respectively) and highly exceeded the limit values established by the Portuguese legislation for indoor air quality. The fungal species most commonly found in bedrooms was Penicillium sp. (91.79%), whereas, in living rooms, it was Rhizopus sp. (37.95%). Aspergillus sections with toxigenic potential were found in bedrooms and living rooms and were able to grow on VOR. Although not correlated with PM, EDC provided information regarding the bioburden. Future studies, applying EDC coupled with PM assessment, should be implemented to allow for a long-term integrated sample of organic dust. Full article

The assessment and control of microbial contamination in health care facilities is presently a mandatory and vital part of strategies to prevent and control hospital-acquired infections. This study aims to assess the bioburden with two passive sampling methods (30 ventilations grids swabs and 16 electrostatic dust collectors (EDCs)) at Clinical Pathology Services. The fungal burden was characterized through molecular tools, antifungal resistance, and the mycotoxins and cytotoxicity profile. Total bacteria presented the highest prevalence in both matrixes, whereas Gram-bacteria presented the lowest. Swabs presented a higher prevalence (27.6%) for fungal burden. Chrysonilia sitophila presented the highest prevalence in swabs, whereas for EDCs, C. sitophila and Mucor sp. were the most prevalent. Concerning Aspergillus genera on swabs, section Flavi was the one with the highest prevalence (58.02%), whereas, for EDCs, section Versicolores was the only section observed (100%). Aspergillus section Fumigati was detected in 10 swabs and 7 EDC samples and Aspergillus section Versicolores was detected in one EDC sample. Fungal growth on azole-supplemented media was observed in eight EDC samples. No mycotoxins were detected in any of the samples. A low cytotoxic effect was observed in two sites upon incubation of collected samples with A549 and SK cells and in two other sites upon incubation of collected samples with SK cells only. A medium cytotoxic effect was observed with one EDC sample upon incubation with A549 cells. This study reinforces the need of determination of the azole resistance profile for fungal species and allowed a preliminary risk characterization regarding the cytotoxicity. An intervention including the use of a ultraviolet with wavelength between 200 nm and 280 nm (UVC)—emitting device and an increased maintenance and cleaning of the central heating, ventilation, and air conditioning (HVAC) systems should be ensured to promote the reduction of microbial contamination. Full article

The indoor microbial community is a mixture of microorganisms resulting from outdoor ecosystems that seed the built environment. However, the biogeography of the indoor microbial community is still inadequately studied. Dust from more than 3000 dwellings across France was analyzed by qPCR using 17 targets: 10 molds, 3 bacteria groups, and 4 mites. Thus, the first spatial description of the main indoor microbial allergens on the French territory, in relation with biogeographical factors influencing the distribution of microorganisms, was realized in this study. Ten microorganisms out of 17 exhibited increasing abundance profiles across the country: Five microorganisms (Dermatophagoïdes pteronyssinus, Dermatophagoïdes spp., Streptomyces spp., Cladosporium sphaerospermum, Epicoccum nigrum) from northeast to southwest, two (Cryptococcus spp., Alternaria alternata) from northwest to southeast, Mycobacteria from east to west, Aspergillus fumigatus from south to north, and Penicillium chrysogenum from south to northeast. These geographical patterns were partly linked to climate and land cover. Multivariate analysis showed that composition of communities seemed to depend on landscapes, with species related to closed and rather cold and humid landscapes (forests, located in the northeast) and others to more open, hot, and dry landscapes (herbaceous and coastal regions, located in the west). This study highlights the importance of geographical location and outdoor factors that shape communities. In order to study the effect of microorganisms on human health (allergic diseases in particular), it is important to identify biogeographic factors that structure microbial communities on large spatial scales and to quantify the exposure with quantitative tools, such as the multi-qPCR approach. Full article

Little research has been conducted in Europe regarding indoor exposure to airborne rodent allergens. The aims of this study were to gain insight into the prevalence of rodent allergens in airborne dust in Dutch households, to assess whether there is a relationship between rodent sightings and detectable allergens, and to identify risk factors associated with the presence of rodent allergens. Airborne dust was collected from the living rooms of 80 households distributed around central Netherlands by passive sampling using electrostatic dust collectors (EDCs). Samples were analysed for mouse (Mus m 1) and rat (Rat n 1) allergens. Participants completed a questionnaire on household and building characteristics, household pets, cleaning habits and ventilation. Mouse allergen was more prevalent than rat allergen and mouse sightings within the past year more than doubled the odds of detectable mouse allergen. Proximity to green areas, ventilation through an open window and insulation under the living room floor were determinants for detectable mouse allergen. Conversely, proximity to surface water was protective. No significant association was found between asthma and detectable mouse allergen. The passive EDC sampling method was used successfully to detect mouse and rat allergens in homes. The presence of mouse allergen was associated with previous mouse sightings. Risk factors and protective factors associated with the presence and levels of mouse allergen were identified. Full article

Several studies reported adverse respiratory health effects in workers exposed to ambient contaminants in bakeries. The aim of this study was to examine worker exposure to fungi and mycotoxins in Portuguese bakeries in order to develop new policies in occupational health. Environmental samples such as air, surfaces, settled dust and electrostatic dust collector (EDC) were collected in 13 bakeries for fungal and mycotoxins assessment. Air samples obtained by impaction were performed applying malt extract agar (MEA) supplemented with chloramphenicol (0.05%) and dichloran glycerol (DG18) agar-based media. Air samples collected through impinger method were determined as well for fungal detection by molecular tools of Aspergillus sections and mycotoxins. The highest median value for fungal load was 1053 CFU·m⁻³ and 65.3% (32 out of 49) of the sampling sites displayed higher fungal load than limits imposed by the World Health Organization. Aspergillus genera was found in air, surface swabs and EDC. Molecular tools were effective in measuring Aspergillus section Fumigati in 22.4% on air, 27.8% on surface swabs and in 7.4% in EDC and Aspergillus section Versicolores in one air sample. All settled dust samples showed contamination with six to eight mycotoxins in each sample. The mycotoxins detected were deoxynivalenol-3-glucoside, deoxynivalenol, zearalenone, 15-acetyldeoxynivalenol, monoacetoxyscirpenol, diacetoxyscirpenol, fumonisin B1, fumonisin B2, griseofulvin, HT2, ochratoxin A, ochratoxin B and mycophenolic acid. Industrial hygienists and exposure assessors should rely on different sampling methods (active and passive) and different assays (culture based and molecular methods) to obtain an accurate risk characterization regarding fungal burden (fungi and mycotoxins). Additionally, the awareness for the raw material as a potential mycotoxins indoor contamination source is important. Full article