Volatile Organic Compounds Removal Efficiency Research Articles

Effect of applying a magnetic field on the biofiltration of hexane over long-term operation period.

The present study reports on the effect of magnetic field (MF) intensity on the biofiltration of hexane vapors. MF ranging from 0 to 30 mT (millitesla) was used to evaluate the biofiltration of hexane for 191days under a fixed inlet load of 40gm-3h-1. A homogeneous MF generated by Helmholtz coils was used. The performance of the reactors was evaluated in terms of removal efficiency (RE), elimination capacity (EC), biomass content, and exopolysaccharide (EPS) production. Maximal removal efficiencies of 25%, 36%, and 40% were found for the control (H0), 10 mT (H10), and 30 mT (H30) reactors, corresponding to ECs of 14.2, 15, and 18gm-3h-1, respectively. In the last period (days 94 to 162), H10 and H30 showed 40% of RE improvement compared with Ho. Also, the removal occurred all along the bioreactor height for biofilters exposed to MF. Reactors achieved a total biomass content of 152, 180, and 147mg VS (volatile solids) g-1 dry perlite for H0, H10, and H30, correspondingly, associated with EPS production of 30, 30, and 40mg EPS g-1 VS. The main components of EPS affected by the MF were carbohydrates and glucuronic acid; proteins were slightly affected. Experiments with MF pulses of 4 and 2h confirmed that MF exposure improved the removal efficiency of hexane, and after the pulse, removal enhancement was maintained for 5days. Thus, the MF application by pulses could be an economically and friendly technology to improve the RE of volatile organic compounds (VOCs).

High‐Performance Ceramic Catalyst Filters with Textured Waveguides for Efficient Removal of Volatile Organic Compounds

AbstractThe cordierite‐based ceramic catalyst filter (CCF) has attracted considerable attention as a promising future air purification system due to its ability to filtrate particulate matter (PM), as well as decompose volatile organic compounds (VOCs) through ultraviolet (UV)‐activated photocatalytic reactions. Its performance, however, is strictly limited because majority of UV photons are absorbed near the entrance of the high‐aspect‐ratio air‐flow channels, thus, only a limited portion of photocatalysts is activated during the flow of polluted air. In this study, a high‐performance CCF is presented featuring textured waveguides (TWs) aligned with an array of UV light‐emitting diodes (LEDs) emitting at a peak wavelength of 365 nm, which are inserted into an array of high‐aspect‐ratio channels. TWs ensure the delivery of UV photons deep inside channels via total internal reflection and scattering, enabling the activation of majority of photocatalysts, resulting in remarkable improvement in VOCs removal efficiency. The proposed CCF system exhibits much higher formaldehyde (HCHO) removal efficiency by 70% compared to conventional CCF systems even subjected to much lower UV light power densities. It is strongly believed that it is possible to further improve the removal efficiency, while maintaining effective PM filtering and ultralow electrical power consumption, by optimization of the geometry of the CCF system with TWs.

Hypercrosslinked Hydrogel Composite Membranes Targeted for Removal of Volatile Organic Compounds via Selective Solution-Diffusion in Membrane Distillation.

Membrane distillation (MD) has attracted considerable interest in hypersaline wastewater treatment. However, its practicability is severely impeded by the ineffective interception of volatile organic compounds (VOCs), which seriously affects the product water quality. Herein, a hypercrosslinked alginate (Alg)/aluminum (Al) hydrogel composite membrane is facilely fabricated via Alg pregel formation and ionic crosslinking for efficient VOC interception. The obtained MD membrane shows a sufficient phenol rejection of 99.52% at the phenol concentration of 100 ppm, which is the highest rejection among the reported MD membranes. Moreover, the hydrogel composite membrane maintains a high phenol interception (>99%), regardless of the feed temperature, initial phenol concentration, and operating time. Diffusion experiments and molecular dynamics simulation verify that the selective diffusion is the dominant mechanism for VOCs-water separation. Phenol experiences a higher energy barrier to pass through the dense hydrogel layer compared to water molecules as the stronger interaction between phenol-Alg compared with water-Alg. Benefited from the dense and hydratable Alg/Al hydrogel layer, the composite membrane also exhibits robust resistance to wetting and fouling during long-term operation. The superior VOCs removal efficiency and excellent durability endow the hydrogel composite membrane with a promising application for treating complex wastewater containing both volatile and nonvolatile contaminants.

Optimization and Simulation Analysis of Furnace Structure for Regenerative Thermal Oxidizer

Volatile Organic Compounds (VOCs) significantly threaten the atmospheric environment. Currently, common methods for the recovery and treatment of VOCs include adsorption, solution absorption, photocatalytic oxidation, and high-temperature oxidation. Among them, the Regenerative Thermal Oxidizer (RTO) is a scheme for high-temperature oxidation treatment of VOCs, which applies aerospace heat transfer and combustion technology to the treatment of VOCs, and the removal efficiency of VOCs can reach over 99%. Considering the high temperature and possible instantaneous overpressure during the combustion process, a three-dimensional flow model of the bottom air distribution chamber and heat storage chamber was established to solve the technical difficulties of the gas flow field in the existing RTO and improve the safety and stability of the overall flow. Simulated the gas flow field and analysed the distribution pattern of the gas flow rate. In response to the uneven distribution of airflow caused by the pipeline layout, orifice plates were installed at the bottom of the furnace, and various orifice plate designs were considered. The results indicate that adding slanted orifice plates can improve flow conditions and enhance safety while meeting practical needs.

Treatment of VOCs with a wet scrubbing – catalytic ozonation process: Efficiency, mechanism and pilot-scale application

A wet scrubbing – catalytic ozonation (WCO) process with activated carbon (AC) loaded MnOx (MnOx/AC) as the catalyst was developed, based on volatile organic compounds (VOCs) can be efficiently removed. The mineralization efficiency, degradation pathway and mechanism, and effects of the process operating parameters were investigated in detail using toluene as the target pollutant. The results show that the average removal efficiency of toluene reached 71.82 % within 90 min under optimal conditions (CToluene = 100 mg/m3; CO3 = 1 mg/L; catalyst loading = 5 g/L; pH = 7; gas flow = 500 mL/min), which outperformed that of the gaseous system. Quenching experiments and electron spin resonance spectroscopy indicate that OH and O2− are the two main reactive oxygen species (ROSs) in the system, which facilitate the opening of the benzene ring and significantly reduce by-products. The intermediates of toluene degradation were identified by proton-transfer reaction time-of-flight mass spectroscopy (PTR-TOF-MS). The results indicate that most of the intermediates generated in the system are captured in water rather than being emitted into the atmosphere. In the pilot-scale experiments, the WCO process exhibited a stable VOC removal efficiency (≥61.05 %) for 10 d in the treatment of actual low-concentration VOCs. Therefore, in this study, an effective process for the removal of low-concentration VOCs is proposed, which can be used for multiple VOC treatments.

Design of bimetallic catalyst with dual-functional Cu-Ce sites for synergistic NOX and toluene abatement

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) coexist in the flue gases from coal-fired power plants and iron/steel smelting industry. In this study, a dual-site catalyst, composed of Cu-Ce-Ti mixed oxide, was screened for the synergistic elimination of NOx and VOCs. The catalyst showed a synergistic removal efficiency above 95% for both C7H8 and NO at 250 °C, and sustain the NOx and VOCs removal efficiencies above 90% even in the presence of 5 vol% H2O and 500 ppm SO2 at 300 °C. Mechanistic studies revealed that the Cu and Ce sites play individual roles in toluene oxidation and NOx reduction, respectively. The primarily occurred SCR reaction facilitated electron exchange through the redox cycling between Ce4+/Ce3+ and Cu2+/Cu+ pairs, resulting in a high abundance of Cu2+ sites being highly active in toluene oxidation. This study could provide new strategy for high-performance catalysts toward synergistic NOx and VOCs abatement.

Development of a CFD model indicating the quantitative relationship among reactor dimension, bed flow unevenness, and performance for VOCs biofilters

ABSTRACT This study presents a Computational Fluid Dynamics (CFD) based biofiltration model to investigate the airflow distribution and the impact of bed flow unevenness (BFU) on the removal of Volatile Organic Compounds (VOCs) in biofilters. The biofiltration model consists of a gas flow sub-model and a VOCs removal sub-model, which were validated by pilot-scale experiments. The model was used to examine the quantitative relationship among reactor dimensions, including the width to height ratio of the filter bed and empty bed residence time (EBRT), BFU, and performance for VOCs biofilters. Simulation results demonstrate that the flow unevenness index (FUI) of the packing layer changes from 0.06 to 0.48 m2‧s−1 with reactor dimension changes. With an increase in the width to height ratio at a constant EBRT, FUI increases, BFU changes, and flow velocity fluctuation on the cross-section becomes larger, leading to a reduction of about 10% in VOCs removal efficiency. Concentration distribution of VOCs becomes uneven in the horizontal direction. At a constant width to height ratio of the filter bed, an increase in EBRT causes an increase in FUI, leading to a decrease in VOCs removal efficiency. When the width to height ratio is 0.5, velocity fluctuation of filter bed cross-section is small, the concentration of VOCs decreases evenly across the filter bed layer, and FUI is at a low level (0.06–0.11 m2‧s−1). Implication: In this manuscript, a biofiltration model of VOCs biofilter based on CFD has constructed and validated. And the manuscript gave the quantitative relationship among reactor dimension, bed flow unevenness and performance for VOCs biofilters for the first time. This study can lead to enhanced VOCs removal efficiency and improved overall performance of biofilters in practical engineering applications.

Catalytic removal of harmful volatile organic compounds by reutilizing zinc rods waste from spent batteries as a palladium catalyst support

The emission of volatile organic compounds (VOCs) has led to significant deterioration in air quality, making it imperative to ensure that these compounds are removed from emission sources before they are released into the atmosphere. In this context, the present study recycled spent primary batteries to use their zinc rods waste (ZRW) as a palladium catalyst support for the removal of harmful VOCs. To this end, palladium supported on ZRW (Pd/ZRW) catalysts were prepared and tested for the catalytic oxidation of benzene, methylbenzene and 1,2-dimethylbenzene. The physicochemical properties of the Pd/ZRW catalysts were carefully characterized by ICP-OES, BET, SEM, XRD, FE-TEM, XPS, and H2-TPR analyses. The main component of ZRW was identified as ZnO. Consistent with expectations, increases in the loading of Pd from 0.1 to 1.0 wt% in the Pd/ZRW catalysts resulted in enhanced VOCs removal efficiency. The reaction temperature required for the complete oxidation (100% removal efficiency) of methylbenzene and 1,2-dimethylbenzene on the 1.0 wt% Pd/ZRW catalyst was below 340 °C at a gas hourly space velocity of 50,000 h−1. TEM, XPS, and H2-TPR results implied that the enhancement of catalytic activity with the addition of Pd could be attributed to the readily movable surface lattice oxygen as well as the active component (Pd species). Ultimately, ZRW of spent primary batteries appear to show promise as a catalyst support for VOCs removal. This study has introduced a novel strategy for reducing air pollutants by utilizing waste, which promotes the disposal of hazardous solid waste and ensures clean air quality.

Self-assembly of MOFs-like materials by Zn2+ and histidine functionalized graphene quantum dots for the efficient removal of VOCs simulants

Volatile organic compounds (VOCs) in the field of printing and packaging, have caused great harm to the environment. Therefore, the removal of volatile organic compounds (VOCs) is a hot topic, and metal-organic frameworks (MOFs) and graphene quantum dots (GQDs) have been applied in this field. However, improving the removal efficiency of different VOCs by using the two kinds of materials is still a great challenge. Herein, ZIF-8 like materials of Zn-His-GQDs were prepared by assembling Zn2+ and histidine functionalized GQDs (His-GQDs) in this work. The morphologies, structure and adsorption performances of Zn-His-GQDs were investigated. These results showed that mesoporous Zn-His-GQDs with a specific surface area of 63.3 m2·g−1 had similar structure to ZIF-8. When the content of Zn-His-GQDs was 200 mg, the equilibrium adsorption capacity for toluene solution of 500 mg·L−1 and ethyl acetate solution of 1600 mg·L−1 was 350 mg·L−1 and 669.44 mg·L−1, respectively. Due to channel filling, cation-π interaction, π-π interaction, hydrogen bond and high surface energy, Zn-His-GQDs exhibited a relative high removal efficiency for high concentration of toluene and ethyl acetate. The removal rate of Zn-His-GQDs on toluene and ethyl acetate after five cycles remained 59.80 % and 36.75 %, respectively. Moreover, this kind of MOFs like materials maintained stable structure during the adsorption in different pH solutions. Therefore, as-prepared Zn-His-GQDs with excellent adsorption performances for typical VOCs simulants in this work have potential application in the treatment of VOCs in the field of printing and packaging.

TiN nanoparticles/OMS-2 nanorods/carbonized wood composites for simultaneous solar water evaporation and abatement of volatile organic compound from undrinkable water

Severe air pollution, water pollution, and climate change have led to an increasing shortage of clean water. Solar interface water evaporation is becoming important to obtain distilled water from undrinkable water such as seawater and contaminated water. However, the as-obtained distilled water usually contains excessive volatile organic compounds (VOCs), which are serious harmful to human health. In this article, a novel bi-functional material is prepared by depositing manganese oxide octahedral molecular sieve (OMS-2) nanorods on carbonized wood (CW), which can simultaneously realize solar water evaporation and VOCs abatement. OMS-2 nanorods synthesized at lower hydrothermal temperature possess higher oxygen vacancy defects, which can improve not only the solar absorption and solar water evaporation rate but also solar driven photothermo-catalytic activity for the oxidation of VOCs. Doping TiN nanoparticles into CW/OMS-2 can further enhance the solar water evaporation performances and VOCs removal efficiencies because of its excellent solar absorption ability, which can further increase the temperature of OMS-2 catalyst and accelerate the solar water evaporation and the toluene degradation. The as-designed bifunctional composites possess an outstanding water evaporation rate over 1.436 kg m−2 h−1 and a toluene removal efficiency of 92.96% under 2.5 sun irradiation, indicating exciting prospects for efficiently producing clean water from undrinkable water with VOCs.

Bibliometrics and Knowledge Map Analysis of Research Progress on Biological Treatments for Volatile Organic Compounds

The emission of volatile organic compounds (VOCs) has resulted in increasingly severe harm to the environment and human health. In recent years, biological methods have become the preferred technology for VOC removal due to their environmental friendliness and economic advantages. Based on the theory of bibliometrics, this study analyzed research articles and reviews on biological methods for VOC removal published in the Web of Science Core Collection (WOSCC) database from 1966 to 2021. The knowledge map visualization software CiteSpace was utilized to analyze research progress in different countries, co-citation clustering, co-citation bursts, and keyword clustering in the literature data. The results indicated that early research on VOC biological treatment focused on the removal of odorous gases and single components of volatile organic waste gases. Subsequently, benzene contents (BTEX), hydrophobic VOCs, and multi-component VOCs have gradually become the focus of research. In recent years, improving VOC removal efficiency by studying packing materials and microbial communities has become an important research topic both domestically and internationally. Future research should focus on continuously improving the performance of reactors, developing novel reactors, and investigating technologies for treating complex and recalcitrant VOCs.

Review of Emission Characteristics and Purification Methods of Volatile Organic Compounds (VOCs) in Cooking Oil Fume

Volatile organic compounds (VOCs) in cooking oil fumes need to be efficiently removed due to the significant damage they cause to the environment and human health. This review discusses the emission characteristics, which are influenced by different cooking temperatures, cooking oils, and cuisines. Then, various cooking oil fume purification methods are mainly classified into physical capture, chemical decomposition, and combination methods. VOCs removal rate, system operability, secondary pollution, application area, and cost are compared. The catalytic combustion method was found to have the advantages of high VOC removal efficiency, environmental protection, and low cost. Therefore, the last part of this review focuses on the research progress of the catalytic combustion method and summarizes its mechanisms and catalysts. The Marse-van Krevelen (MVK), Langmuir-Hinshelwood (L-H), and Eley-Rideal (E-R) mechanisms are analyzed. Noble metal and non-noble metal catalysts are commonly used. The former showed excellent activity at low temperatures due to its strong adsorption and electron transfer abilities, but the high price limits its application. The transition metals primarily comprise the latter, including single metal and composite metal catalysts. Compared to single metal catalysts, the interaction between metals in composite metal catalysts can further enhance the catalytic performance.

Electrospun Cyclodextrin/Poly(L-lactic acid) Nanofibers for Efficient Air Filter: Their PM and VOC Removal Efficiency and Triboelectric Outputs.

In this work, PLLA and CD/PLLA nanofibers were fabricated using electrospinning and utilized as a particulate matter (PM) and volatile organic compounds (VOCs) filter. The electrospun PLLA and CD/PLLA were characterized with various techniques, including SEM, BET, FTIR, XRD, XPS, WCA, DSC, tensile strength testing, PM and VOCs removal efficiency, and triboelectric performance. The results demonstrated that the best air filter was 2.5 wt%CD/PLLA, which performed the highest filtration efficiencies of 96.84 ± 1.51% and 99.38 ± 0.43% for capturing PM2.5 and PM10, respectively. Its PM2.5 removal efficiency was 16% higher than that of pure PLLA, which were contributed by their higher surface area and porosity. These 2.5 wt%CD/PLLA nanofibers also exhibited the highest and the fastest VOC entrapment. For triboelectric outputs, the 2.5 wt%CD/PLLA-based triboelectric nanogenerator provided the highest electrical outputs as 245 V and 84.70 μA. These give rise to a three-fold enhancement of electrical outputs. These results indicated that the 2.5 wt%CD/PLLA can improve surface charge density that could capture more PM via electrostatic interaction under surrounding vibration. Therefore, this study suggested that 2.5 wt%CD/PLLA is a good candidate for a multifunction nanofibrous air filter that offers efficient PM and VOC removal.

Optimization of metals degradation and vitrification from fly ash using Taguchi design combined with plasma pyrolysis and recycling in cement construction

Fly ash has been widely recognized as the hazardous waste due to its toxicity to environment. It should be treated properly for preventing the high contamination to the environment and generate volatile organic compounds (VOCs) from the pyrolysis treatment. The aim of this study is to investigate the most influenced parameters in elimination of elements, vitrification and destruction of volatile organic compounds (VOCs) from the fly ash via a plasma pyrolysis with the combination of Taguchi method and recycling it into the cement construction, which potentially applied in the real application. The combination of fly ash treatment with CaCO3, SiO2, Al2O3 and glass gives the high removal efficiency of VOCs at 4.653 ppm under the nitrogen plasma. Furthermore, the gas flow rate has the most significant impact on the destruction of elements based on the Taguchi analysis. The best removals of element are known as follows: Hg>Cd>Se>As>Cr>Pb>Cu. Lastly, compressive test of the cement at age 28 days with the substitution of 10% fly ash confirmed greater result on cement quality. The most influenced parameter, namely gas flow rates with the combination of flux agents are thus suggested for degrading harmful elements and VOCs. Fly ash from plasma post-treatment has the potential for replacing the cement material when used in the construction material to implemented the recycling concept.

Progress in Adsorptive Removal of Volatile Organic Compounds by Zeolites

Volatile Organic Compounds (VOCs) are a class of pollutants that have recently received much attention in atmospheric and indoor air pollution problems. They are precursors for PM2.5 and ozone generation. The removal of VOCs emitted from exhaust gases is an urgent problem to solve air pollution. Adsorption is one of the most promising VOC abatement technologies, with the advantages of high purification efficiency, low cost, and simple equipment. The adsorbent plays a critical role in VOCs removal efficiency. Zeolite is a rapidly developing material due to its highly ordered and flexible microporous structure, good stability, and abundant surface modification. In this paper, the influence of zeolite properties, including framework structure, pore properties, and surface cations, on VOCs adsorption performance is analyzed. The VOCs adsorption performance on different zeolite adsorbents in the presence of water vapor is compared. The influential factors on the mass transfer kinetic properties of VOCs adsorption are summarized. Finally, an overview of zeolite honeycomb adsorbent applications for industrial use is presented, including multi-tower fixed bed adsorption and zeolite rotor adsorption.

Application of different packing media for the biofiltration of gaseous effluents from waste composting

ABSTRACT A pilot-scale experiment was implemented in a waste bioreactor with an inner capacity of 1 m3 in order to simulate a real-scale composting process. The waste underwent composting conditions that are typical of the initial bio-oxidation phase, characterised by a high production of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and odorants. The waste bioreactor was fed with an intermittent airflow rate of 6 Nm3/h. The target of this study was to investigate the air treatment performance of three biofilters with the same size, but filled with different filtering media: (1) wood chips, (2) a two-layer combination of lava rock (50%) and peat (50%), and (3) peat only. The analyses on air samples taken upstream and downstream of the biofilters showed that the combination of lava rock and peat presents the best performance in terms of mean removal efficiency of odour (96%), total VOCs (95%) and H2S (77%) concentrations. Wood chips showed the worst abatement performance, with respective mean removal efficiencies of 90%, 88% and 62%. From the results obtained, it is possible to conclude that the combination of lava rock and peat can be considered as a promising choice for air pollution control in waste composting facilities.

Synthesis of CeyMn(1-y)Ox solid solution catalysts with superior photothermal catalytic performance for acetone removal under ambient condition

Cerium-manganese solid solution catalysts were prepared by sol-gel method. X-ray diffraction, Raman, UV–Vis-IR diffuse reflectance spectroscopy, and H2 temperature programmed reduction (H2-TPR) were used to characterize the as-prepared catalysts. Introduction of Mnx+ into CeO2 lattice dramatically improved the full solar spectrum absorption ability, as well as the lattice oxygen mobility of the catalysts. The Ce0.25Mn0.75Ox catalyst presents much better low temperature reducibility due to the presence of readily reduced Mnx+ species in CeO2 lattice. Ce0.25Mn0.75Ox shows a superior photothermal catalytic activity for the degradation of gaseous acetone under visible-infrared irradiation (150 mW/cm2), which gives a reaction rate constant of 11.0 times higher than that with MnOx. During the whole process, the air temperature in catalytic system never exceeds 42 °C, suggesting the achievement of the efficient photothermal catalysis for acetone removal under ambient condition. This work provides an alternative strategy in environmental protection field for efficient volatile organic compounds removal in indoor environment.

Removal of Gaseous Volatile Organic Compounds by a Multiwalled Carbon Nanotubes/Peroxymonosulfate Wet Scrubber.

In this study, a wet scrubber coupled with a persulfate-based advanced oxidation process [carbocatalysts/peroxymonosulfate (PMS)] was demonstrated to efficiently remove gaseous volatile organic compounds (VOCs). The removal efficiency of a representative VOC, styrene, was stable at above 98%, and an average mineralization rate was achieved at 76% during 2 h. The removal efficiency of the carbocatalysts/PMS wet scrubber for styrene was much higher than that of pure water, carbocatalysts/water, or PMS/water systems. Quenching experiments, electron spin resonance spectroscopy, in-situ Raman spectroscopy and density functional theory (DFT) calculations indicated that singlet oxygen (1O2) and oxidative complexes are the main reactive oxygen species and that both contributed to styrene removal. In particular, carbonyl groups (C═O) in the carbocatalyst were found to be the active sites for activating PMS during styrene oxidation. The role of 1O2 was discovered to be benzene ring breaking and a possible non-radical oxidation pathway of styrene was proposed based on time-of-flight mass spectroscopy which was further verified by DFT calculations. In particular, the electron transfer process of multi world carbon nanotubes-PMS* in styrene oxidation was further studied in-depth by experiments and DFT calculations. The unstable vinyl on styrene was simultaneously degraded by the oxidative complexes and 1O2 into benzene, and finally oxidized by 1O2 into H2O and CO2. This study provides an effective method for VOC removal and clearly illustrates the complete degradation mechanism of styrene in a nonradical PMS-based process by a wet scrubber.

Occurrence, health risk, and removal efficiency assessment of volatile organic compounds in drinking water treatment plants (DWTPs): An investigation of seven major river basins across China

The presence of volatile organic compounds (VOCs) in drinking water has the potential to harm human health and undermine public confidence. Hence, this is the first study to comprehensively investigate concentrations of 25 VOCs in the 146 drinking water treatment plants (DWTPs) in 24 cities across seven major river basins (including the Yangtze River, Yellow River, Haihe River, Songhua River, Liaohe River, Pearl River, and Huaihe River), China. The occurrence, human health, and olfactory risks, as well as removal efficiency of VOCs in DWTPs, were evaluated. The findings revealed that 21 VOCs were detected, with concentrations ranging from not detected to 99.10 μg/L (trichloromethane). The maximum concentrations of trichloroacetaldehyde (54.90 μg/L) and trichloromethane (99.10 μg/L) exceeded China's regulated values (GB 5749–2006/2022). The concentrations of VOCs and water quality parameters showed a strong positive correlation. Human health and olfactory risks assessment indicated that drinking water exposures do not pose carcinogenic (CR < 10−6) and non-carcinogenic (HI < 1) health risks to consumers, nor do olfactory and taste hazards (OHI <1). However, it is worth mentioning that due to the relatively high concentrations of some VOCs (trichloroacetaldehyde, acrolein, and trichloromethane), the health risk posed by them are still a major concern that needs to be addressed. Finally, the removal efficiency of VOCs is low in 146 DWTPs (mean of 12.91%–76.79%). Taken together, adding advanced treatment procedures for the purpose of improving the removal efficiency of pollutants of DWTPs in the future is an urgent priority.

Preferential removal of aromatics-dominated electronic industrial emissions using the integration of spray tower and photocatalysis technologies

Industrial emissions from the manufacturing of printed circuit boards (PCBs) are characterized by low concentration and high gas flow rates, and are one of the important sources of toxic and odorous volatile organic compounds (VOCs). They are deleterious to human health and considered as important precursors for the formation of ozone. Herein, we conducted a case study in which an integrated decontamination technique consisting of a spray tower (ST) and photocatalysis (PC) was applied to purify the waste gas emitted from a PCB manufacturing facility. Total of 66 VOCs including halogenated hydrocarbons (HHs), aromatic hydrocarbons (AHs), oxygen-containing hydrocarbons (OVOCs), and aliphatic hydrocarbons (AIHs) were quantified using GC-MS during four sampling events. The results showed that AHs were the largest group (contributing >85.0% of the total VOCs). The average removal efficiency (RE) of VOCs during the nine months’ continuous treatment was 72.39%. High RE was attributed to the following three aspects: the capture efficiencies of HHs with slight water solubility (50.16% of RE) and AIHs with low saturation pressure (54.75% of RE) were improved by the process consisting of ST upstream of PC, whereas AHs was preferentially degraded by PC (61.34% of RE). In addition, the ozone formation potential and the health risk (cancer and non-cancer risks) greatly decreased after the ST-PC treatment. This study suggests that ST-PC technique is a promising approach for removing continuously emitted organic waste gas with low concentration and high gas flow rates, as well as reducing the ozone formation and risk of health hazards.