Study on the ability of indoor plants to absorb and purify benzene pollution.

The ability of indoor plants to purify benzene pollution is the basic basis for the selection of plants for ecological remediation of indoor benzene pollution. In this study, the purification rate and the purification amount per unit leaf area of 13 test plants at three benzene concentrations were determined by indoor fumigation experiments, and the benzene absorption and purification abilityability of indoor plants were comprehensively evaluated. The results showed that (1) there was a significant correlation between benzene concentration and purification rate and purification amount per unit leaf area. (2) At the three concentrations, Spathiphyllum floribundum showed the highest purification rate and Sansevieria trifasciata var. laurentii showed the highest purification per unit leaf area. (3) The combined results showed that Sansevieria trifasciata var. laurentii, Spathiphyllum floribundum and Aloe arborescens were the strongest absorbers and purifiers, while Podocarpus nagi and Anthurium andraeanum 'Pink champin' had the weakest absorption and purification capacity. The results of this study provide a theoretical basis and reference for the selection of plants with strong capacities to adsorb and purify benzene pollution in indoor air.

Continuous air purification by aqueous interface filtration and absorption.

The adverse impact of particulate air pollution on human health1,2 has prompted the development of purification systems that filter particulates out of air3-5. To maintain performance, the filter units must inevitably be replaced at some point, which requires maintenance, involves costs and generates solid waste6,7. Here we show that an ion-doped conjugated polymer-coated matrix infiltrated with a selected functional liquid enables efficient, continuous and maintenance-free air purification. As the air to be purified moves through the system in the form of bubbles, the functional fluid provides interfaces for filtration and for removal of particulate matter and pollutant molecules from air. Theoretical modelling and experimental results demonstrate that the system exhibits high efficiency and robustness: its one-time air purification efficiency can reach 99.6%, and its dust-holding capacity can reach 950 g m-2. The system is durable and resistant to fouling and corrosion, and the liquid acting as filter can be reused and adjusted to also enable removal of bacteria or odours. We anticipate that our purification approach will be useful for the development of specialist air purifiers that might prove useful in a settings such as hospitals, factories and mines.

Hierarchical Porous Recycled PET Nanofibers for High-Efficiency Aerosols and Virus Capturing.

Plastic crisis, especially for poly(ethylene terephthalate) (PET) bottles, has been one of the greatest challenges for the earth and human beings. Processing recycled PET (rPET) into functional materials has the dual significance of both sustainable development and economy. Providing more possibilities for the engineered application of rPET, porous PET fibers can further enhance the high specific surface area of electrospun membranes. Here, we use a two-step strategy of electrospinning and postprocessing to successfully control the surface morphology of rPET fibers. Through a series of optical and thermal characterizations, the porous morphology formation mechanism and crystallinity induced by solvents of rPET fibers were discussed. Then, this work further investigated both PM2.5 air pollutants and protein filtration performance of rPET fibrous membrane. The high capture capability of rPET membrane demonstrated its potential application as an integrated high-efficiency aerosol filtering solution.

A case-control study of airborne dissemination of bacteria during CT colonography.

OBJECTIVES: The COVID-19 pandemic has highlighted the importance of aerosol spread of infection. We have conducted a study to detect bacterial contamination of room surfaces and room air during CT colonography and confirm the efficacy of room disinfection procedures carried out between examinations. METHODS: Systematic sampling of the CT examination couch and horizontal surfaces 1 m and 3 m from the couch was performed before and after patient examinations. A 1 m3 sample of room air was obtained during patient examinations. Samples were processed using routine laboratory methods. A case-control study design was used (30 CT colonography and 30 routine body CT scans). RESULTS: Evidence of airborne dissemination of bacteria was detected in >30% of CT colonography examinations and <10% of control examinations (p = 0.01). No pathogenic bacteria were detected in surface samples taken before patient examinations. CONCLUSION: The room disinfection policy in use in our CT department is effective in eliminating pathogenic bacteria from surfaces in the patient environment. CT colonography causes contamination of room air with enteric bacteria in a significant proportion of cases. ADVANCES IN KNOWLEDGE: CT colonography may possibly be an aerosol-generating procedure. Larger-scale investigation is needed to fully evaluate this potential infection risk.

Identification of the phase composition of solid microparticles in the nasal mucosa of patients with chronic hypertrophic rhinitis using Raman microspectroscopy.

Solid particles, predominantly in micron and submicron sizes, have repeatedly been observed as a threat to a human health unique compared to the other textures of the same materials. In this work, the hypothesis the solid metal-based particles play a role in the pathogenesis of chronic hypertrophic rhinitis was investigated in patients who had not responded positively to medication. In the group of 40 randomly selected patients indicated for surgical mucotomy, the presence of solid micro- and submicron particles present in their nasal mucosa was assessed. For comparison, a set of 13 reference samples from patients without diagnosed chronic hypertrophic rhinitis was evaluated. The analysis was performed using Raman microspectroscopy. The advantage of this method is the direct identification of compounds. The main detected compounds in the mucosa samples of patients with chronic hypertrophic rhinitis were TiO2, carbon-based compounds, CaCO3, Ca(Fe, Mg, Mn)(CO3)2 MgCO3, Fe2O3, BaSO4, FeCO3 and compounds of Al and Si, all of which may pose a health risk to a living organism. In the reference samples, only TiO2 and amorphous carbon were found. In the control group mucosa, a significantly lower presence of most of the assessed compounds was found despite the longer time they had to accumulate them due to their higher mean age. Identification and characterisation of such chemicals compounds in a living organism could contribute to the overall picture of the health of the individual and lead to a better understanding of the possible causes not only in the chronic hypertrophic rhinitis, but also in other mucosal and idiopathic diseases.

Observing ozone chemistry in an occupied residence.

Outdoor ozone transported indoors initiates oxidative chemistry, forming volatile organic products. The influence of ozone chemistry on indoor air composition has not been directly quantified in normally occupied residences. Here, we explore indoor ozone chemistry in a house in California with two adult inhabitants. We utilize space- and time-resolved measurements of ozone and volatile organic compounds (VOCs) acquired over an 8-wk summer campaign. Despite overall low indoor ozone concentrations (mean value of 4.3 ppb) and a relatively low indoor ozone decay constant (1.3 h-1), we identified multiple VOCs exhibiting clear contributions from ozone-initiated chemistry indoors. These chemicals include 6-methyl-5-hepten-2-one (6-MHO), 4-oxopentanal (4-OPA), nonenal, and C8-C12 saturated aldehydes, which are among the commonly reported products from laboratory studies of ozone interactions with indoor surfaces and with human skin lipids. These VOCs together accounted for ≥12% molecular yield with respect to house-wide consumed ozone, with the highest net product yield for nonanal (≥3.5%), followed by 6-MHO (2.7%) and 4-OPA (2.6%). Although 6-MHO and 4-OPA are prominent ozonolysis products of skin lipids (specifically squalene), ozone reaction with the body envelopes of the two occupants in this house are insufficient to explain the observed yields. Relatedly, we observed that ozone-driven chemistry continued to produce 6-MHO and 4-OPA even after the occupants had been away from the house for 5 d. These observations provide evidence that skin lipids transferred to indoor surfaces made substantial contributions to ozone reactivity in the studied house.

Cytotoxic Effects of Water-Soluble Extracts of Coarse and Fine Atmospheric Particulate Matter on Mast Cell Lines.

Fine particulate matter (PM2.5) pollution causes serious health disorders, because PM2.5 becomes deposited in the tracheobronchial and alveoli regions. In the extrathoracic region, there are more deposits of coarse particulate matter than fine particulates. As adverse health issues caused by coarse particulates have not been well investigated, this study examined the cytotoxicity of water-soluble extracts of both fine (0.05-3 µm, PM0.05-3) and coarse (> 3 µm, PM>3) particulates collected from April 2016 to March 2019 in Fukuoka, Japan. Also evaluated were concentrations of NH4+ and SO42-, multi-components of well-known secondary generation substances. The findings revealed that PM>3 showed stronger cytotoxic effects on mast cell lines than PM0.05-3. Cytotoxic effects were observed at concentrations of over 15 mM of (NH4)2SO4 and over 30 mM of NH4Cl. In contrast, Na2SO4 caused few cytotoxic effects up to a concentration of 50 mM. The causative substances for this cytotoxicity may not have been NH4+ and SO42- because their PM>3 concentrations indicating the largest cytotoxic effects were 1 and 0.4 mM, respectively. The cytotoxicities of PM>3 and PM0.05-3 were the highest in the first half of FY2016. These cytotoxicities seem to be due to cross-border pollution, although this pollution has been declining in recent years. An increasing trend of cytotoxicity was observed in the second half of FY2018. This study showed that cytotoxicity and particulate concentrations are not always correlated. Thus, we should focus not only on the quantity of atmospheric particulate matter, but also on its quality.

Microbiological examination of water and aerosols from four industrial evaporative cooling systems in regard to risk of Legionella emissions and methodological suggestions for surveillance.

The hygienic risk associated with evaporative cooling systems in Germany is currently only assessed by determining concentrations of Legionella spp. in the corresponding cooling waters. Relevant for the health risk is however the load of Legionella in emitted aerosols. In this work aerosol emissions from four industrial cooling systems (A - D) were analyzed. A microbiological air bioburden factor (MABF) is suggested to be useful to assess the overall microbiological load of emitted air and to judge the efficiency of droplet separation and overall microbiological retention. Whereas the MABF by itself only serves as a technical quality assurance (QA) parameter, the hygienic relevance has to be seen in combination with the assessment of Legionella either contained in the aerosol or in the cooling water. Plate counting of colonies was an appropriate method to quantify Legionella spp. in aerosols given the short time of flight at the chosen sampling locations and resulting low risk of desiccation. qPCR data on the other hand proved more reproducible than the culture approach to quantify Legionella spp. concentrations in cooling water-. The application of qPCR also allowed to assess the relative proportion of Legionella pneumophila within the total pool of Legionella which adds epidemiological relevance to risk assessment. A traffic light system was proposed to guide interpretation of qPCR data. The four industrial systems greatly differed in all measured parameters leading to different associated risks.

Juncus effusus fiber-based cellulose cigarette filter with 3D hierarchically porous structure for removal of PAHs from mainstream smoke.

Polycyclic aromatic hydrocarbons (PAHs) from cigarettes are one of the main pollutants affecting public health. Herein, a cellulose cigarette filter with three-dimensional (3D) hierarchically porous structure was fabricated using a natural cellulose Juncus effusus (JE) fiber, whose pore size was well controlled by biocompatible polyvinylpyrrolidone (PVP) using a simple dip-dry method. The adsorption capacity and mechanism of the PVP-JE filter tips (PJF) against PAHs were investigated in detail. Compared with conventional cellulose acetate filter tips (CAF), the cellulose PJF were superior at filtering and adsorbing of PAHs from mainstream smoke with the removal efficiency of 61.79 %, which was 22.57 % higher than that of CAF (39.22 %). The ternary structures including polymer filter membrane, 3D network, and interconnected channels were demonstrated as the main roles for highly effective removal of PAHs. The JE-based cellulose cigarette filter can be a promising candidature to broaden the application range of polysaccharide in pollutant elimination.

Removal of particulate matter from pork belly grilling gas using an orifice wet scrubber.

Grilling restaurants are a major contributor to airborne particulate matter (PM) in metropolitan areas. In this study, the removal of PM during the grilling of pork belly using an orifice scrubber, which is a form of gas-induced spray scrubber, was assessed. During grilling, the particle mass concentration was the highest for 1.0 < PM ≤ 2.5 µm (55.5% of total PM emissions), followed by 0.5 < PM ≤ 1.0 (27.1%), PM ≤ 0.5 (10.7%), and PM > 2.5 µm (7.0%). The PM removal efficiency of the orifice scrubber at a gas flow of 4.5 m3 min-1 was > 99.7% for PM ≥ 2.5 µm, 89.4% for 1.0 < PM ≤ 2.5 µm, 62.1% for 0.5 < PM ≤ 1.0, and 36.5% for PM ≤ 0.5 µm. Although further research is necessary to optimize its use, the orifice scrubber offers a user-friendly technology for the control of PM in small grilling restaurants because of its simple design, uncomplicated operation, and satisfactory PM removal performance.

Dynamic performance of a fungal biofilter packed with perlite for the abatement of hexane polluted gas streams using SIFT-MS and packing characterization with advanced X-ray spectroscopy.

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.

Assessment of antibiotic resistant coliforms from bioaerosol samples collected above a sewage-polluted river in La Paz, Bolivia.

Antimicrobial resistance is a global health risk, and the presence of resistant bacteria in the environment may be an indicative of fecal pollution. The objective of this study has been to assess the antibiotic resistance of airborne coliforms near a highly impacted urban river that may contain high levels of fecal waste. The pilot study has been located within an Andean river basin, the Choqueyapu River basin, which flows through La Paz city in Bolivia. Bioaerosol samples have been collected using liquid impingement and plated on mTEC agar. Coliforms have been detected within 80% of the air samples. The resistance profiles of coliforms present in 20 air samples have been determined by using a modified Kirby-Bauer disk diffusion test against amoxicillin-clavulanic acid, ciprofloxacin, gentamicin, meropenem, sulfamethoxazole-trimethoprim, and tetracycline, antibiotics commonly used to treat gram-negative infection. Broad patterns of antibiotic resistance have been observed throughout the study, with coliforms from at least one sample exhibiting resistance to each of the tested antibiotics. Resistance to sulfamethoxazole and amoxicillin-clavulanic acid has been the most commonly observed, with coliforms in 73% and 60% of samples which helps to demonstrate resistance to these antibiotics, respectively. This study provides insight into the prevalence of airborne, antibiotic resistant coliforms near concentrated fecal waste streams and this highlights an underappreciated hazard and the potential exposure risk in areas where fecal waste may become aerosolized at any given time.

Effect of hydrophobic fumed silica addition on a biofilter for pentane removal using SIFT-MS.

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.

Pattern Recognition and Anomaly Detection by Self-Organizing Maps in a Multi Month E-nose Survey at an Industrial Site.

Currently people are aware of the risk related to pollution exposure. Thus odor annoyances are considered a warning about the possible presence of toxic volatile compounds. Malodor often generates immediate alarm among citizens, and electronic noses are convenient instruments to detect mixture of odorant compounds with high monitoring frequency. In this paper we present a study on pattern recognition on ambient air composition in proximity of a gas and oil pretreatment plant by elaboration of data from an electronic nose implementing 10 metal-oxide-semiconductor (MOS) sensors and positioned outdoor continuously during three months. A total of 80,017 e-nose vectors have been elaborated applying the self-organizing map (SOM) algorithm and then k-means clustering on SOM outputs on the whole data set evidencing an anomalous data cluster. Retaining data characterized by dynamic responses of the multisensory system, a SOM with 264 recurrent sensor responses to air mixture sampled at the site and four main air type profiles (clusters) have been identified. One of this sensor profiles has been related to the odor fugitive emissions of the plant, by using ancillary data from a total volatile organic compound (VOC) detector and wind speed and direction data. The overall and daily cluster frequencies have been evaluated, allowing us to identify the daily duration of presence at the monitoring site of air related to industrial emissions. The refined model allowed us to confirm the anomaly detection of the sensor responses.

Characteristics and interactions of bioaerosol microorganisms from wastewater treatment plants.

Bacteria and fungi are abundant and ubiquitous in bioaerosols from wastewater treatment plants (WWTPs). However, the specificity and interactions of bioaerosol microorganism, particularly of potential pathogens, from WWTPs are still poorly understood. In this study, we investigated 9 full-scale WWTPs in different areas of China for 3 years, and found microbial variations in bioaerosols to be associated with regions, seasons, and processes. Relative humidity, total suspended particulates, wind speed, temperature, total organic carbon, NH4+, Cl- and Ca2+ were the major factors influencing this variation, and meteorological factors were more strongly associated with the variation than chemical composition. In total, 95 and 22 potential bacterial and fungal pathogens were detected in bioaerosols, respectively. The linear discriminant analysis effect size method suggested that Serratia, Yersinia, Klebsiella, and Bacillus were discriminative genera in bioaerosols on the whole, and were also hub niches in the interactions within potential bacterial pathogens, based on network analysis. Strong co-occurrences such as Serratia-Bacillus and Staphylococcus-Candida, and co-exclusions such as Rhodotorula-Cladosporium and Pseudomonas-Candida, were found within and between potential bacterial and fungal pathogens in bioaerosols from WWTPs. This study furthers understanding of the biology and ecology of bioaerosols from WWTPs, and offers a theoretical basis for determining bioaerosol control.

Vertical Profiles of Pollution Particle Concentrations in the Boundary Layer above Paris (France) from the Optical Aerosol Counter LOAC Onboard a Touristic Balloon.

Atmospheric pollution by particulate matter represents a significant health risk and needs continuous monitoring by air quality networks that provide mass concentrations for PM10 and PM2.5 (particles with diameter smaller than 10 m and 2.5 m, respectively). We present here a new approach to monitor the urban particles content, using six years of aerosols number concentration measurements for particles in the 0.2-50 m size range. These measurements are performed by the Light Optical Aerosols Counter (LOAC) instrument onboard the tethered touristic balloon "Ballon de Paris Generali", in Paris, France. Such measurements have allowed us first to detect at ground a seasonal variability in the particulate matter content, due to the origin of the particles (anthropogenic pollution, pollens), and secondly, to retrieve the mean evolution of particles concentrations with height above ground up to 150 m. Measurements were also conducted up to 300 m above ground during major pollution events. The vertical evolution of concentrations varies from one event to another, depending on the origin of the pollution and on the meteorological conditions. These measurements have shown the interest of performing particle number concentrations measurements for the air pollution monitoring in complement with regulatory mass concentrations measurement, to better evaluate the intensity of the pollution event and to better consider the effect of smallest particles, which are more dangerous for human health.

Identification of most preferable reaction pathways for chloride depletion from size segregated sea-salt aerosols: A study over high altitude Himalaya, tropical urban metropolis and tropical coastal mangrove forest in eastern India.

Depletion of chloride from sea-salt aerosols affects their hygroscopicity, cloud condensation nuclei activity as well as microphysical and chemical properties of aerosols and clouds modifying earth-atmosphere radiative balance. Here, we proposed five possible reaction pathways through which the inorganic acids (H2SO4 and HNO3) could deplete chloride from sea-salt aerosols. We determined "maximum potential contribution" (MPC) of each acid and compared the MPC with actual chloride depletion. This step-by-step approach enables us to identify the most preferable reaction pathway(s) for coarse, superfine, accumulation and ultrafine aerosols over a Himalayan station (Darjeeling), a tropical urban station (Kolkata) and a tropical mangrove forest at the north-east coast of Bay of Bengal (Sundarban) in India. Over Kolkata and Darjeeling, locally generated acids reacted with transported sea-salts. Over Sundarban, the locally generated sea-salts from the Bay of Bengal reacted with the acids of biomass burning plume transported from Eastern Ghat and continental haze transported from upper Indo-Gangetic Plain. The average chloride depletion in PM10 ranged between 70 and 74% over Sundarban and 31-34% over Kolkata and Darjeeling. We observed that HNO3(g) depleted the larger (>1 µm) chlorides whereas H2SO4(g) depleted the smaller (<1 µm) chlorides over Kolkata and Darjeeling. However, in addition to H2SO4(g) and HNO3(g), some other species could be involved in chloride depletion over Sundarban mainly during winter. The study reveals that Sundarban acts as the major sink of the inorganic acids transported from Eastern Ghat biomass burning plume inhibiting their further advection towards inland regions.

Numerical simulation of the simultaneous removal of particulate matter in a wet flue gas desulfurization system.

The particulate matter (PM) could be simultaneously removed during the wet flue gas desulfurization (WFGD) process. To analyze the underlying mechanism and removal efficiency, the PM removal process in a desulfurization system was numerically simulated based on the population balance model and general dynamics equation in this study. The equation was solved using the fixed-step Monte Carlo method to determine the PM removal characteristics under different working conditions (such as spray intensity, velocity of the flue gas, and layers of slurry spray). When the flue gas velocity decreased from 7 to 3 m/s, the removal efficiency increased from 90.93 to 93.52%, and when the mean geometric droplet size decreased from 3 to 1 mm, the removal efficiency increased from 67.18 to 99.14%. Besides, large diameter PM was more easily removed by the desulfurization system. Thus, the numerical simulation method was proven to be feasible by comparing these results with field measurements of a WFGD system in a coal-fired power plant.

A combined microextraction procedure for isolation of polycyclic aromatic hydrocarbons in ambient fine air particulate matter with determination by gas chromatography-tandem mass spectrometry.

A novel combined vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME)-micro-solid-phase extraction (µ-SPE) procedure for polycyclic aromatic hydrocarbons (PAHs) in ambient fine particulate matter of aerodynamic diameter of  ≤ 2.5 µm (PM2.5), was developed. PM2.5 was collected on polytetrafluoroethylene (PTFE)-coated glass fiber filter, that was first processed by ultrasonicating in aqueous solution. Then, VA-DLLME, followed by µ-SPE, were applied to the solution using 1-octanol and graphene oxide as extractant and sorbent, respectively for extracting the PAHs. The PAHs were determined by gas chromatography-tandem mass spectrometry (GC-MS/MS). Parameters affecting the extraction efficiency including selection of the sorbent, duration of DLLME and µ-SPE, desorption solvent type, and ultrasonication-assisted desorption time were investigated. Under the optimum extraction conditions, the method exhibited linear ranges of 0.5-50 µg/L and 0.5-100 µg/L depending on the analytes. The limits of detection were in the range of 0.013 µg/L-0.135 µg/L. The developed method was applied to determine the PAHs in genuine PM2.5 samples collected on PTFE glass fiber filters. The concentration levels in the atmospheric PM2.5 were determined to be from below the limit of quantification to 0.135 ng/m3. The relative recoveries obtained from spiked concentrations at 1 µg/L and 5 µg/L were in the range 57-88% with relative standard deviations <14%.

Removal of toluene vapor in the absence and presence of a quorum-sensing molecule in a biotrickling filter and microbial composition shift.

Toluene is highly toxic and mutagenic, and it is generally used as an industrial solvent. Thus, toluene removal from air is necessary. To solve the problem of reducing high toluene concentrations with a short gas retention time (GRT), a quorum-sensing molecule [N-(3-oxododecanoyl)-L-homoserine lactone] (OHL) was added to a biotrickling filter (BTF). In this study, a BTF was used to treat synthetic and natural waste gases containing toluene. An extensive analysis was performed to understand the removal efficiency, removal characteristics, and bacterial community of the BTF. The addition of 20 µM OHL to the BTF significantly improved toluene removal, and more than 99.2% toluene removal was achieved at a GRT of 0.5 min when natural waste gas containing toluene (590-1020 ppm or 2.21-3.83 g m-3) was introduced. The maximum inlet load for toluene was 337.9 g m-3 h-1. Moreover, the BTF exhibited satisfactory adaptability to shock loading and shutdown operations. Pseudomonadaceae (33.0%) and Comamonadaceae (26.3%) were predominant bacteria in the system after a 98-day operation. These bacteria were responsible for toluene degradation. The optimal moisture content and low pressure drop for system operations demonstrated that the BTF was energy and cost efficient. Therefore, processing through a BTF with OHL is a favorable technique for toluene treatment.