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1.
PLoS One ; 15(9): e0239531, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946526

RESUMO

The worldwide shortage of single-use N95 respirators and surgical masks due to the COVID-19 pandemic has forced many health care personnel to use their existing equipment for as long as possible. In many cases, workers cover respirators with available masks in an attempt to extend their effectiveness against the virus. Due to low mask supplies, many people instead are using face coverings improvised from common fabrics. Our goal was to determine what fabrics would be most effective in both practices. Under laboratory conditions, we examined the hydrophobicity of fabrics (cotton, polyester, silk), as measured by their resistance to the penetration of small and aerosolized water droplets, an important transmission avenue for the virus causing COVID-19. We also examined the breathability of these fabrics and their ability to maintain hydrophobicity despite undergoing repeated cleaning. Laboratory-based tests were conducted when fabrics were fashioned as an overlaying barrier for respirators and when constructed as face coverings. When used as material in these two situations, silk was more effective at impeding the penetration and absorption of droplets due to its greater hydrophobicity relative to other tested fabrics. We found that silk face coverings repelled droplets in spray tests as well as disposable single-use surgical masks, and silk face coverings have the added advantage over masks such that they can be sterilized for immediate reuse. We show that silk is a hydrophobic barrier to droplets, can be more breathable than other fabrics that trap humidity, and are re-useable via cleaning. We suggest that silk can serve as an effective material for making hydrophobic barriers that protect respirators, and silk can now be tested under clinical conditions to verify its efficacy for this function. Although respirators are still the most appropriate form of protection, silk face coverings possess properties that make them capable of repelling droplets.


Assuntos
Betacoronavirus , Infecções por Coronavirus/prevenção & controle , Máscaras/normas , Pandemias/prevenção & controle , Equipamento de Proteção Individual/normas , Pneumonia Viral/prevenção & controle , Seda/normas , Têxteis/normas , Filtração/métodos , Humanos , Interações Hidrofóbicas e Hidrofílicas , Equipamento de Proteção Individual/virologia , Dispositivos de Proteção Respiratória
2.
Int J Hyg Environ Health ; 229: 113582, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32917368

RESUMO

The recent outbreak of the coronavirus disease (COVID-19) is causing a shortage of personal protective equipment (PPE) in different countries around the world. Because the coronavirus can transmit through droplets and aerosols, facemasks and N95 respirators that require complex certification, are urgently needed. Given the situation, the U.S. Centers for Disease Control and Prevention (CDC) recommends that "in settings where facemasks are not available, healthcare personnel might use homemade masks (e.g., bandana, scarf) for the care of patients with COVID-19 as a last resort." Although aerosols and droplets can be removed through the fibers of fabrics through a series of filtration mechanisms, their filtration performances have not been evaluated in detail. Moreover, there are a series of non-medical materials available on the market, such as household air filters, coffee filters, and different types of fabrics, which may be useful when facemasks and respirators are not available. In this study, we comprehensively evaluated the overall and size-dependent filtration performances of non-medical materials. The experiments were conducted under different face velocities to study its influence on size-dependent filtration performances. The flow resistance across these filter materials is measured as an indicator of the breathability of the materials. The results illustrate that multiple layers of household air filters are able to achieve similar filtration efficiencies compared to the N95 material without causing a significant increase in flow resistance. Considering that these air filters may shed micrometer fibers during the cutting and folding processes, it is recommended that these filters should be inserted in multiple layers of fabrics when manufacturing facemasks or respirators.


Assuntos
Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/prevenção & controle , Filtração/métodos , Máscaras/normas , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Dispositivos de Proteção Respiratória/normas , Aerossóis/análise , Humanos , Exposição por Inalação/prevenção & controle , Teste de Materiais , Têxteis/virologia , Estados Unidos
3.
ACS Chem Neurosci ; 11(18): 2786-2788, 2020 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-32870651

RESUMO

Herein, we propose the use of novel adsorbents, namely micelle clay complexes comprising the clay montmorillonite, coupled with activated carbon for effective eradication of neuropathogenic microbes such as SARS-CoV-2 and Naegleria fowleri from water supplies for ablution/nasal irrigation. These can be incorporated easily to water collection devices, i.e., taps and water bottles, in the domestic setting. These filters are low cost, easy to install, and ideal disinfection systems. Such strategies are particularly useful for communities who have lack of access to safe water supplies, rely heavily on water storage tanks, or lack adequate water sanitation facilities, especially in developing countries.


Assuntos
Infecções por Coronavirus/prevenção & controle , Filtração/métodos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Purificação da Água/métodos , Bentonita , Betacoronavirus , Infecções Protozoárias do Sistema Nervoso Central/prevenção & controle , Carvão Vegetal , Argila , Filtração/instrumentação , Humanos , Naegleria fowleri , Lavagem Nasal , Purificação da Água/instrumentação
5.
Chemosphere ; 260: 127630, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32758778

RESUMO

Biological treatment processes have the potential to remove organic micropollutants (OMPs) during water treatment. The OMP removal capacity of conventional drinking water treatment processes such as rapid sand filters (RSFs), however, has not been studied in detail. We investigated OMP removal and transformation product (TP) formation in seven full-scale RSFs all treating surface water, using high-resolution mass spectrometry based quantitative suspect and non-target screening (NTS). Additionally, we studied the microbial communities with 16S rRNA gene amplicon sequencing (NGS) in both influent and effluent waters as well as the filter medium, and integrated these data to comprehensively assess the processes that affect OMP removal. In the RSF influent, 9 to 30 of the 127 target OMPs were detected. The removal efficiencies ranged from 0 to 93%. A data-driven workflow was established to monitor TPs, based on the combination of NTS feature intensity profiles between influent and effluent samples and the prediction of biotic TPs. The workflow identified 10 TPs, including molecular structure. Microbial community composition analysis showed similar community composition in the influent and effluent of most RSFs, but different from the filter medium, implying that specific microorganisms proliferate in the RSFs. Some of these are able to perform typical processes in water treatment such as nitrification and iron oxidation. However, there was no clear relationship between OMP removal efficiency and microbial community composition. The innovative combination of quantitative analyses, NTS and NGS allowed to characterize real scale biological water treatments, emphasizing the potential of bio-stimulation applications in drinking water treatment.


Assuntos
Água Potável/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Bélgica , Compostos Férricos , Filtração/métodos , Microbiota , Países Baixos , Nitrificação , RNA Ribossômico 16S/genética , Areia
6.
Ecotoxicol Environ Saf ; 203: 110945, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32684517

RESUMO

The high-concentration wastewater produced in the industrial reverse osmosis (RO) process contains a large amount of refractory organic matters, which will have serious impacts on the natural environment and human health. Among them, contaminants can be transformed by humus-reducing bacteria based on humus. In this study, O3- assisted UV-Fenton method was applied as pretreatment. Biological activated carbon (BAC) technology in which humus-reducing bacteria were the dominant bacteria, enhanced by electron donor and Fe3+, was used to dispose of RO concentrate (ROC). The results showed that water treatment process combining oxidation with biological filtration had a positive effect on the removal of stubborn contaminants in ROC. The system was strengthened by adding electron donor and Fe3+, and the chemical oxygen demand (COD) removal efficiency was up to 80.1%. However, when the removal efficiency of UV254 absorbing pollutants reached optimal value (87.3%), that means only Fe3+ was added.


Assuntos
Carvão Vegetal/análise , Compostos Férricos/química , Substâncias Húmicas , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Filtração/métodos , Substâncias Húmicas/análise , Substâncias Húmicas/microbiologia , Hidrocarbonetos Halogenados/análise , Peróxido de Hidrogênio/química , Ferro/química , Osmose , Oxirredução , Ozônio/química , Raios Ultravioleta , Águas Residuárias/análise , Águas Residuárias/microbiologia
7.
Chemosphere ; 260: 127514, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688309

RESUMO

The main aim of this study was to evaluate the performance of an air membrane bioreactor (aMBR) for the treatment of gas-phase methanol. A laboratory-scale hollow fiber aMBR was operated for 150 days, at inlet methanol concentrations varying between 2 and 30 g m-3 and at empty bed residence times (EBRT) of 30, 10 and 5 s. Under steady-state conditions, a maximum methanol removal efficiency (RE) of 98% was obtained at an EBRT of 30 s and a decrease in RE of methanol was observed at lower EBRTs. On increasing the inlet loading rate, some portion of gas-phase MeOH was stripped into the liquid phase due to its solubility in water. Under transient conditions, the MeOH removal efficiency dropped from an average value of 95%-90% after 5 h of 10-fold shock load and dropped from an average value of 95%-88% under 5-fold increase in shock load. During transient-state tests, the aMBR performed well under different upset loading conditions and a drop in RE of ∼ 5-10% was observed. However, the aMBR performance was restored within 1-2 days when pre-shock conditions were restored. The results from microbial structure analysis revealed a big shift of the dominant methanol degrader, from Candida boidinii strain TBRC 217 to Xanthobacter sp. and Fusicolla sp., respectively.


Assuntos
Poluentes Atmosféricos/análise , Reatores Biológicos/microbiologia , Membranas Artificiais , Metanol/análise , Biodegradação Ambiental , Biofilmes/crescimento & desenvolvimento , Candida/crescimento & desenvolvimento , Desenho de Equipamento , Filtração/métodos , Xanthobacter/crescimento & desenvolvimento
8.
Chemosphere ; 259: 127328, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32610174

RESUMO

This study investigates five different fouling models and contributing factors in membrane-filtration blocking mechanisms in a constant-pressure mode. A polyvinylidene fluoride membrane was used to study the fouling effects of a complex mixture of foulants (a latex-bed suspension, soybean oil, and inorganics) on pristine and chemically cleaned membranes in the presence of humic acid. A significance ratio in linear regression results (p-value) was used to assess the contribution of fouling mechanism in each model. The results indicate that Hermia and Bowen's models correspond closely with the experiment results and confirms that complete blocking is dominant fouling model. We also verify that each developed model is dependent on its experimental conditions. Moreover, the role of complex mixtures, including inorganic foulants, in the fouling process needs to be modified as modified for ceramic membranes and natural organic matter removal in the Wiesner and Kilduff models, respectively.


Assuntos
Incrustação Biológica , Membranas Artificiais , Purificação da Água/métodos , Cerâmica , Filtração/métodos , Substâncias Húmicas , Fenômenos Físicos
9.
Chemosphere ; 258: 127278, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554006

RESUMO

Syringe filters are widely used for sample pretreatments in laboratories. This study found that, surprisingly, these filters can leak dissolved organic carbon (DOC) that can potentially serve as precursors of disinfection by-products (DBPs). Nine common types of syringe filters were assessed. The results showed that the DOC of ultrapure water increased after syringe filtration. The DOC shed from filter membranes was characterized, whose spectra showed that the main compounds exhibited a low apparent molecular weight. Five classes of DBPs were investigated including trihalomethanes, haloacetaldehydes, haloacetonitriles, haloacetamides and halonitromethanes, among which trichloromethane (TCM), dichloroacetaldehyde (DCAL), trichloroacetaldehyde (TCAL), dichloroacetonitrile (DCAN), and trichloronitromethane (TCNM) were principally detected. The DBP formation was affected by chlorination time and membrane types. In general, the use of the poly vinylidene fluoride membrane resulted in the highest formation of TCM and TCAL, whereas nylon and mixed cellulose esters membranes contributed significantly to the formation of DCAN and TCNM, respectively. The shedding DOC and the formation of TCM, DCAL and TCAL from filter membranes were mitigated effectively by pre-washing; however, the contribution of membrane leakage to DCAN and TCNM formation was still notable, even with a pre-wash volume of 50 mL. When unwashed syringe filters were used for a real water sample, the DBP formation increased by up to 73.2% compared to the pre-washed ones; particularly for TCNM it was always over 15%. Therefore, for better quality control in laboratories, more attention should be paid to the syringe filters during sample pre-treatments, particularly when DBP formation is being investigated.


Assuntos
Desinfetantes/análise , Desinfetantes/química , Desinfecção/métodos , Membranas Artificiais , Acetonitrilos/análise , Acetonitrilos/química , Clorofórmio/análise , Clorofórmio/química , Cromatografia em Gel , Filtração/instrumentação , Filtração/métodos , Halogenação , Hidrocarbonetos Clorados/análise , Hidrocarbonetos Clorados/química , Peso Molecular , Trialometanos/análise , Trialometanos/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Purificação da Água/métodos
10.
Chemosphere ; 257: 127198, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32512329

RESUMO

Filters of various structures (filter by pore depth or pore width) and pore sizes are used to extract microplastics (<5 mm) in researches. In present study, we demonstrate that filters with different structures and pore sizes can lead to different outcomes in microplastic filtering. Our results showed that when filtering large-sized microplastics, nylon filter (double-layer-hole type) retained nearly 100% of fibers, while polycarbonate filter (single-layer-hole type) only retained 61.7%. Polycarbonate filter retained the most fragments (80.8%), while cotton fiber filter (multilayer-hole type) retained the least (54.4%). Pellets were retained on different layers of nylon and cotton fiber filters, and could not be quantified accurately. Additionally, the sizes of some fibers and fragments captured were not within the expected ranges by lattice-knitting filters. Large fiber (3568.0 µm) was not filtered out after 1000 µm pore-size filtration. Small fragment (37.2 µm) was found on 50 µm pore-size filters. To validate laboratory results, filed waters containing microplastics (∼90% in form of fibers) were filtered through different pore-size filters. As expected, the relationship between abundance and pore size followed a same trend as that in laboratory fiber samples. Thereby, our results indicated that filter structure and pore size could affect the abundances of microplastics with different shapes. To obtain more accurate abundance of microplastics in a wide size range, and to consider filtration duration, size limitation of observation, and spatial resolution of identification instrument, we recommend that water samples should be filtered using 20 µm pore-size filters with a double-layer-hole type of structure.


Assuntos
Microplásticos , Modelos Químicos , Monitoramento Ambiental , Filtração/métodos , Plásticos , Cimento de Policarboxilato , Polímeros
11.
Eur J Trauma Emerg Surg ; 46(4): 731-735, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32488448

RESUMO

BACKGROUND: Surgery in the era of the current COVID-19 pandemic has been curtailed and restricted to emergency and certain oncological indications, and requires special attention concerning the safety of patients and health care personnel. Desufflation during or after laparoscopic surgery has been reported to entail a potential risk of contamination from 2019-nCoV through the aerosol generated during dissection and/or use of energy-driven devices. In order to protect the operating room staff, it is vital to filter the released aerosol. METHODS: The assemblage of two easily available and low-cost filter systems to prevent potential dissemination of Coronavirus via the aerosol is described. RESULTS: Forty-nine patients underwent laparoscopic surgeries with the use of one of the two described tools, both of which proved to be effective in smoke evacuation, without affecting laparoscopic visualization. CONCLUSION: The proposed systems are cost-effective, easily assembled and reproducible, and provide complete viral filtration during intra- and postoperative release of CO2.


Assuntos
Infecções por Coronavirus , Filtração/métodos , Controle de Infecções/métodos , Laparoscopia , Pandemias , Pneumonia Viral , Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Transmissão de Doença Infecciosa/prevenção & controle , Serviços Médicos de Emergência/métodos , Desenho de Equipamento , Humanos , Laparoscopia/efeitos adversos , Laparoscopia/instrumentação , Laparoscopia/métodos , Salas Cirúrgicas/métodos , Salas Cirúrgicas/tendências , Pandemias/prevenção & controle , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Pneumoperitônio Artificial/métodos , Gestão da Segurança/métodos
12.
Am J Infect Control ; 48(8): 883-889, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32464294

RESUMO

OBJECTIVE: The past 4 months, the emergence and spread of novel 2019 SARS-Cov-2 (COVID-19) has led to a global pandemic which is rapidly depleting supplies of personal protective equipment worldwide. There are currently over 1.6 million confirmed cases of COVID-19 worldwide which has resulted in more the 100,000 deaths. As these numbers grow daily, hospitals are being forced to reuse surgical masks in hopes of conserving their dwindling supply. Since COVID-19 will most likely have effects that last for many months, our nationwide shortage of masks poses a long term issue that must be addressed immediately. METHODS: Based on a previous study by Quan et al., a salt-based soaking strategy has been reported to enhance the filtration ability of surgical masks. We propose a similar soaking process which uses materials widely available in anyone's household. We tested this method of pretreating a variety of materials with a salt-based solution by a droplet test using fluorescently stained nanoparticles similar in size to the COVID-19 virus. RESULTS: In this study, we found that paper towels and surgical masks pretreated with the salt-based solution showed a noticeable increase in filtration of nanoparticles similar in size to the COVID-19 virus. We also show that the TWEEN20 used by Quan et al. is not a critical component for the solution, and using salt alone in solution still provides a dramatically increased level of protection. CONCLUSIONS: We believe this method will allow for healthcare workers to create a disposable added layer of protection to their surgical masks, N95s, or homemade masks by using household available products. Adoption of this method may play an essential role in ensuring the safety of healthcare workers during the COVID-19 pandemic and any pandemics that may arise in the future.


Assuntos
Infecções por Coronavirus/prevenção & controle , Filtração/métodos , Transmissão de Doença Infecciosa do Paciente para o Profissional/prevenção & controle , Máscaras/virologia , Pandemias/prevenção & controle , Equipamento de Proteção Individual/microbiologia , Pneumonia Viral/prevenção & controle , Betacoronavirus/patogenicidade , Pessoal de Saúde , Humanos , Cloreto de Sódio/química
13.
PLoS One ; 15(5): e0233522, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32437479

RESUMO

Environmental DNA (eDNA) analysis has gained traction as a precise and cost-effective method for species and waterways management. To date, publications on eDNA protocol optimization have focused primarily on DNA yield. Therefore, it has not been possible to evaluate the cost and speed of specific components of the eDNA protocol, such as water filtration and DNA extraction method when designing or choosing an eDNA protocol. At the same time, these two parameters are essential for the experimental design of a project. Here we evaluate and rank 27 different eDNA protocols in the context of Chinook salmon (Oncorhynchus tshawytscha) eDNA detection in an estuarine environment. We present a comprehensive evaluation of multiple eDNA protocol parameters, balancing time, cost and DNA yield. We collected samples composed of 500 mL estuarine water from Deverton Slough (38°11'16.7"N 121°58'34.5"W) and 500 mL from tank water containing 1.3 juvenile Chinook Salmon per liter. Then, we compared extraction methods, filter types, use of inhibitor removal kit for DNA yield, processing time, and protocol cost. Lastly, we used an MCMC algorithm together with machine learning to understand the DNA yield of each step of the protocol as well as the interactions between those steps. Glass fiber filtration was to be the most resilient to high turbidites, filtering the samples in 2.32 ± 0.08 min instead of 14.16 ± 1.86 min and 6.72 ± 1.99 min for nitrocellulose and paper filter N1, respectively. The filtration DNA yield percentages for paper filter N1, glass fiber, and nitrocellulose were 0.00045 ± 0.00013, 0.00107 ± 0.00013, 0.00172 ± 0.00013. The DNA extraction yield percentage for QIagen, dipstick, NaOH, magnetic beads, and direct dipstick ranged from 0.047 ± 0.0388 to 0.475 ± 0.0357. For estuarine waters, which are challenging for eDNA studies due to high turbidity, variable salinity, and the presence of PCR inhibitors, we found that a protocol combining glass filters, magnetic beads, and an extra step for PCR inhibitor removal, is the method that best balances time, cost, and yield. In addition, we provide a generalized decision tree for determining the optimal eDNA protocol for other studies in aquatic systems. Our findings should be applicable to most aquatic environments and provide a clear guide for determining which eDNA protocol should be used under different study constraints.


Assuntos
DNA Ambiental/análise , Monitoramento Ambiental/métodos , Animais , DNA Ambiental/genética , Filtração/métodos , Reação em Cadeia da Polimerase/métodos , Salmão/genética , Água/análise
14.
Chemosphere ; 255: 126977, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402891

RESUMO

The simultaneous removal of nitrate (15 mg N-NO3- L-1) and phosphate (12 mg P-PO43- L-1) from nutrient-polluted synthetic water was investigated in a recirculated pyrite-packed biofilter (RPPB) under hydraulic retention time (HRT) ranging from 2 to 11 h. HRT values ≥ 8 h resulted in nitrate and phosphate average removal efficiency (RE) higher than 90% and 70%, respectively. Decrease of HRT to 2 h significantly reduced the RE of both nitrogen and phosphorus. The RPPB showed high resiliency as reactor performance recovered immediately after HRT increase to 5 h. Solid-phase characterization of pyrite granules and backwashing material collected from the RPPB at the end of the study revealed that iron-phosphate, -hydroxide and -sulfate precipitated in the bioreactor. Thermodynamic modeling predicted the formation of S0 during the study. Residence time distribution tests showed semi-complete mixing hydrodynamic flow conditions in the RPPB. The RPPB can be considered an elegant and low-cost technology coupling biological nitrogen removal to the recovery of phosphorus, iron and sulfur via chemical precipitation.


Assuntos
Reatores Biológicos , Desnitrificação , Filtração/métodos , Ferro , Fósforo/isolamento & purificação , Sulfetos , Precipitação Química , Filtração/instrumentação , Ferro/isolamento & purificação , Nitrogênio/isolamento & purificação , Enxofre/química , Enxofre/isolamento & purificação
15.
Chemosphere ; 253: 126684, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32464772

RESUMO

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m-3 h-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D µCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.


Assuntos
Óxido de Alumínio , Poluentes Ambientais/isolamento & purificação , Filtração/métodos , Fungos , Hexanos/isolamento & purificação , Dióxido de Silício , Poluentes Atmosféricos/isolamento & purificação , Biodegradação Ambiental , Biomassa , Fusarium/crescimento & desenvolvimento , Fusarium/metabolismo , Análise Espectral/métodos
16.
Chemosphere ; 254: 126738, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32339799

RESUMO

Biofiltration is a typical air pollution control process for the treatment of volatile organic compounds (VOCs). Mass transfer of hydrophobic VOCs to the biofilm is limited which leads to low removal efficiency (RE). Aiming to enhance the transport of hydrophobic VOCs, the effect of hydrophobic fumed silica (HFS) addition to a biofilter (BF) for pentane removal was studied in this paper. The effect of HFS on pentane removal was evaluated by daily RE measurements and periodical headspace gas pentane pulse injections using SIFT-MS as analysis apparatus. The BF was operated during more than 100 days at an empty bed residence time (EBRT) of 120 s reaching an elimination capacity (EC) up to 93.8 g pentane m-3 h-1. At the last stage of the study, when a higher nutrient pulse and HFS to a concentration of 1.5% w/w wet were added, the BF showed better EC (46.3 ± 14.9 g pentane m-3 h-1; RE = 96.2%) compared to the previous stages (28.3 ± 4.4 g pentane m-3 h-1; RE = 68.3%). This overall performance improvement was in line with the short peak perturbation experiments carried out during the operational time which demonstrated, by net retention time (NRT) determination, to be a fast and reliable tool to gain insights into the behaviour of pollutants inside the BF and its state. Pentane demonstrated to have larger interactions with the packing material when HFS was added. NRT/EBRT ratio variated along the whole operational time, being larger at the last stage.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Filtração/métodos , Pentanos/isolamento & purificação , Dióxido de Silício/farmacologia , Compostos Orgânicos Voláteis/isolamento & purificação , Poluentes Atmosféricos/análise , Biodegradação Ambiental , Biofilmes , Filtração/instrumentação , Interações Hidrofóbicas e Hidrofílicas , Compostos Orgânicos Voláteis/análise
17.
PLoS One ; 15(4): e0231475, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32330139

RESUMO

The threat of arsenic contamination to public health, particularly in developing countries, has become a serious problem. Millions of people in their daily lives are still highly dependent on groundwater containing high levels of arsenic, which causes excessive exposure to this toxic element, due to the high cost and lack of water-treatment infrastructures. Therefore, a technique for large-scale treatment of water in rural areas to remove arsenic is needed and should be low-cost, be easily customized, and not rely on electrical power. In this study, in an effort to fulfill those requirements, we introduce a three-dimensional (3D), printed water-filtration system for arsenic removal. Three-dimensional printing can provide a compact, customized filtration system that can fulfill the above-mentioned requirements and that can be made from plastic materials, which are abundant. Armed with the versatility of 3D printing, we were able to design the internal surface areas of filters, after which we modified the surfaces of the 3D, printed filters by using iron (III) oxide as an adsorbent for arsenite. We investigated the effects of the controlled surface area on the flow rate and the deposition of the adsorbent, which are directly related to the adsorption of arsenic. We conducted isotherm studies to quantify the adsorption of arsenic on our 3D, printed filtration system.


Assuntos
Arsênico/química , Arsenitos/química , Filtração/métodos , Poluentes Químicos da Água/química , Purificação da Água/métodos , Água/química , Adsorção , Água Subterrânea/química , Ferro/química
18.
Chemosphere ; 251: 126358, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32155493

RESUMO

Acidic substances, which produced during chlorinated volatile organic compounds, will corrode the commonly used packing materials, and then affect the removal performance of biofiltration. In this study, three biofilters with different filter bed structure were established to treat gaseous chlorobenzene. CaCO3 and 3D matrix material was added in filter bed as pH buffering material and filter bed supporting material, respectively. A comprehensive investigation of removal performance, biomass accumulation, microbial community, filter bed height, voidage, pressure drops, and specific surface area of the three biofilters was compared. The biofilter with CaCO3 and 3D matrix material addition presented stable removal performance and microbial community, and greater biomass density (209.9 kg biomass/m3 filter bed) and growth rate (0.033 d-1) were obtained by using logistic equation. After 200 days operation, the height, voidage, pressure drop, specific surface area of the filter bed consisted of perlite was 27.4 cm, 0.39, 32.8 Pa/m, 974,89 m2/m3, while those of the filter bed with CaCO3 addition was 28.2 cm, 0.43, 21.3 Pa/m, and 1021.03 m2/m3, and those of the filter bed with CaCO3 and 3D matrix material addition was 28.7 cm, 0.55, 17.4 Pa/m, and 1041.60 m2/m3. All the results verified the biofilter with CaCO3 and 3D matrix material addition is capable of sustaining the long-term performance of biofilters. CaCO3 could limit the changes of removal efficiency, microbial community and filter bed structure by buffering the pH variation. And 3D matrix material could maintain the filter bed structure by supporting the filter bed, regardless of the buffering effect.


Assuntos
Clorobenzenos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Óxido de Alumínio , Biomassa , Filtração/métodos , Gases , Concentração de Íons de Hidrogênio , Dióxido de Silício , Compostos Orgânicos Voláteis/química
19.
Chemosphere ; 251: 126404, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32169711

RESUMO

The removal efficiency (RE) and bioaerosol emission of a perlite biofilter treating vapors of toluene (T) and/or ethyl acetate (EA) were assessed, under different operating conditions, during 171 days. Under the first stages of operation, a mixture of EA and T was treated, with equivalent inlet loads (ILs) of each compound (ranging from 26 to 84 g m-3 h-1), achieving a 100% RE of EA, and a maximum elimination capacity (EC) of T of 58.7 g m-3 h-1. An inhibition of T removal was noted in presence of EA, as T was treated subsequently to EA, along biofilter depth. A 17 days starvation period induced no global deterioration of performance regarding EA removal, but a 50% lower RE of T. Suspension of one contaminant, with interspersed feeding of only one component of the mixture, caused a permanent drop of the RE of EA (to 87.3%), after a T only feeding of 41 days. Flow cytometry (FC) was applied for quantification of bioaerosols, allowing for differentiation between viable, dead and damaged cells. During the overall biofilter operation, bioaerosol emission was not statistically different from bioaerosol retention. However, the biofilter significantly emitted bioaerosols (mostly viable cells) during start-up and IL increase, whereas a global retention of dead cells was observed during the interspersed feeding of one contaminant. Bioaerosols measured by FC (107 Cells m-3) were three orders of magnitude greater than with plate counting dishes, indicating that FC does not underestimate bioaerosols as culture dependent techniques.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Biodegradação Ambiental , Acetatos , Filtração/métodos , Citometria de Fluxo , Gases , Tolueno/análise
20.
Chemosphere ; 252: 126490, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32220715

RESUMO

Hydrophilic VOCs (volatile organic compounds) were applied to explore their positive influence on the elimination of the single hydrophobic VOC in biotrickling filters (BTFs). Comparison experiments were carried to evaluate the effect of 4-methyl-2-pentanone and toluene on the performance of BTFs for n-hexane removal. The results showed that the existence of 4-methyl-2-pentanone improved the removal performance of BTFs at short gas empty bed contact time (EBRT) of 15 s and low temperature of 10 °C. The degradation of n-hexane in the presence of 4-methyl-2-pentanone was slightly enhanced with a loading ratio of 6:1. When the mixing ratio was greater than 4, toluene significantly promoted the biodegradation of n-hexane with toluene loading rate less than 10 g m-3 h-1. Additionally, The promotion effect was not only reflected in the contents of proteins and polysaccharides, but also in the growth rates of microorganisms in biofilms. This work discussed the detailed effect between n-hexane and hydrophilic VOCs in BTFs, which would contribute to develop a more economical method to improve the removal performance of hydrophobic VOCs in BTFs.


Assuntos
Poluentes Atmosféricos/química , Reatores Biológicos , Hexanos/química , Compostos Orgânicos Voláteis/química , Poluentes Atmosféricos/análise , Biodegradação Ambiental , Biofilmes , Filtração/métodos , Interações Hidrofóbicas e Hidrofílicas , Metil n-Butil Cetona , Tolueno , Compostos Orgânicos Voláteis/análise
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