Integration of a nonmetallic electrostatic precipitator and a wet scrubber for improved removal of particles and corrosive gas cleaning in semiconductor manufacturing industries

To remove particles in corrosive gases generated by semiconductor industries, we have developed a novel non-metallic, two-stage electrostatic precipitator (ESP). Carbon brush electrodes and grounded carbon fiber-reinforced polymer (CFRP) form the ionization stage, and polyvinyl chloride collection plates are used in the collection stage of the ESP The collection performance of the ESP downstream of a wet scrubber was evaluated with KC1, silica, and mist particles (0.01-10 pm), changing design and operation parameters such as the ESP length, voltage, and flow rate. A long-term and regeneration performance (12-hr) test was conducted at the maximum operation conditions of the scrubber and ESP and the performance was then demonstrated for 1 month with exhaust gases from wet scrubbers at the rooftop of a semiconductor manufacturing plant in Korea. The results showed that the electrical and collection performance of the ESP (16 channels, 400x400 mm2) was maintained with different grounded plate materials (stainless steel and CFRP) and different lengths of the ionization stage. The collection efficiency of the ESP at high air velocity was enhanced with increases in applied voltages and collection plate lengths. The ESP (16 channels with 100 mm length, 400x400 mm2x540 mm with a 10-mm gap) removed more than 90% of silica and mistparticles with 10 and 12 kV applied to the ESPat the air velocity of 2 m/s and liquid-to-gas ratio of 3.6 L/m3. Decreased performance after 13 hours ofcontinuous operation was recovered to the initial performance level by 5 min of water washing. Moreover during the 1-month operation at the demonstration site, the ESP showed average collection efficiencies of 97% based on particle number and 92% based on total particle mass, which were achieved with a much smaller specific corona power of 0.28 W/m3/hr compared with conventional ESPs.     

Feasibility study on cross-linked biopolymeric concrete encapsulating selenium glass wastes

Feasibility study was conducted to encapsulate the selenium (Se) contained in glass waste, using the biopolymer-modified concrete. Biopolymer has unique characteristics to provide the chemical sites to metals or toxic compounds through the three-dimensional cross-linked structure. Very minute amount of biopolymer enhanced the characteristics of cementitious material. The resulting biopolymeric composite with selenium glass waste showed 20% higher compressive strength than ordinary concrete and the lower leaching concentration than the equipment detection limit. For a qualitative measurement, X-ray diffraction (XRD; X-ray powder diffractogram) was used to characterize the biopolymeric concrete. The optimum waste content percentage with appropriate biopolymer concrete mixture ratio was identified for its possible commercial use.     

Enzymatic and microbial transformation assays for the evaluation of the environmental fate of diclofenac and its metabolites

Diclofenac has been of environmental concern due to the potential harmful effects on non-target organisms at environmentally relevant concentrations. In this study, we evaluated the transformation kinetics of diclofenac and its two major metabolites in two laboratory-scale experiments: the transformation of diclofenac in the presence of rat liver S9 fraction with co-factors, and the transformation of diclofenac, 4′-hydroxy-diclofenac and diclofenac β-O-acyl glucuronide in the inoculum used for the OECD 301C ready-biodegradability test. 4′-Hydroxy-diclofenac was identified as the major phase I metabolite and diclofenac β-O-acyl glucuronide was identified as the major phase II metabolite in the S9 assay. Transformation of diclofenac in the microbial degradation test did not occur significantly for 28 d, whereas 4′-hydroxy-diclofenac degraded slowly, indicating that the biological removal of diclofenac is not likely to occur in conventional STPs unless sorptive removal is significant. However, diclofenac β-O-acyl glucuronide deconjugated to form equimolar diclofenac within 7 d, in the microbial degradation test. The mixture of diclofenac and its two metabolites, formed after incubating diclofenac in S9 medium for 2 h, was spiked in the inoculum to link both assays. The concentrations of diclofenac and its metabolites, measured over time, agreed well with predicted values, using rate parameters obtained from independent experiments. The results show that phase II metabolites generated in mammals may deconjugate easily in conventional STPs to form a parent compound and that these processes should be considered during the environmental monitoring and risk assessment of diclofenac.     

Effect of seepage conditions on chemical attenuation of arsenic by soils across an abandoned mine site

The effect of seepage velocity on the As leaching/adsorption by soils collected from abandoned mine sites was evaluated under batch equilibrium and different seepage settings. The breakthrough curves (BTCs) of As leaching from the mine soil column initially displayed the peak export and gradually leveled off over the leaching experiment. A similar As peak was observed after a flow interruption period. Adsorption by downgradient soils was clearly nonlinear, as Freundlich N was <1. In the BTCs of the layered columns, where downgradient soils were overloaded above the mine soil, the extended lag period of As appearance and lower steady-state As concentration observed for slow seepage velocity supported the idea of kinetically limited As attenuation driven by soil adsorption. The perturbation of As concentration was insignificant when the intra-column As concentration gradient was higher. The As concentration drop and time to recovery were greater for less adsorptive soil and fast seepage velocity. Desorption of As from soils retrieved from both batch adsorption and column experiment demonstrate hysteric behavior. The results of this work demonstrated that the risk of As leaching from an abandoned mine site can be greatly attenuated by intermediate downgradient soils via chemical adsorption, which tends to be kinetically limited and energetically hysteric (i.e., non-identical energy pathway).     

Columnar aerosol optical and radiative properties according to season and air mass transport pattern over East Asia

The column-integrated optical and radiative properties of aerosols in the downwind area of East Asia were investigated based on sun/sky radiometer measurements performed from February 2004 to June 2005 at Gwangju (35.23° N, 126.84° E) and Anmyeon (36.54° N, 126.33° E), Korea. The observed aerosol data were analyzed for differences among three seasons: spring (March-May), summer (June-August), and autumn/winter (September-February). The data were also categorized into five types depending on the air mass origin in arriving in the measurement sites: (a) from a northerly direction in spring (S(N)), (b) from a westerly direction in spring (S(W)), (c) cases with a low ?ngstr?m exponent (<0.8) in spring (dust), (d) from a northerly direction in autumn/winter (AW(N)), and (e) from a westerly direction during other seasons (AW(W)). The highest ?ngstr?m exponents (α) at Gwangju and Anmyeon were 1.43?±?0.30 and 1.49?±?0.20, respectively, observed in summer. The lowest column-mean single-scattering albedo (ω) at 440 nm observed at Gwangju and Anmyeon were 0.89?±?0.02 and 0.88?±?0.02, respectively, during a period marked by the advection of dust from the Asian continent. The highest ω values at Gwangju and Anmyeon were 0.95?±?0.02 and 0.96?±?0.02, respectively, observed in summer. Variations in the aerosol radiative-forcing efficiency (β) were related to the conditions of the air mass origin. The forcing efficiency in summer was -131.7 and -125.6 W?m(-2) at the surface in Gwangju and Anmyeon, respectively. These values are lower than those under the atmospheric conditions of spring and autumn/winter. The highest forcing efficiencies in autumn/winter were -214.3 and -255.9 W?m(-2) at the surface in Gwangju and Anmyeon, respectively, when the air mass was transported from westerly directions.     

The role of local governments before and during chemical accidents,focusing on changes in hazardous chemical management systems

ABSTRACT

Disaster management spans actions before, during, and after disaster events. Changes in the roles and functions of local governments before a disaster can influence other stages of disaster management. After a chemical spill in 2012, South Korean hazardous chemical management tasks were returned to the central government and local governments’ roles and functions were reduced. To identify associated issues and enhance the hazardous chemical management system, this study analyzed changes in laws and policies and conducted interviews with stakeholders. While the changes helped with centralization, reinforcement, and specification, some loopholes were discovered. The information and human resource capacities of local governments and intra – and intergovernmental relations issues have hindered their active participation before and during chemical disasters. These loopholes can be addressed through institutional enhancements for local governments, such as including them in monitoring hazardous chemical handling facilities, developing codes articulating the division of tasks among departments within them, and providing adequate incentives for them to increase their personnel. This study provides empirical data that informs ongoing debates about the centralization and devolution of disaster management by linking local governments’ ordinary management systems to their disaster management activities.     

Market potential of biomethane as alternative transportation fuel in South Korea

This study estimated domestically available energy amount of biomethane including landfill gas (LFG) as a transportation fuel by 2035. The amount of available energy that could be supplied was predicted through four stages of ‘theoretical-’, ‘geographical-’, ‘technical-’, and ‘market potential’ by considering geographical, technical, economic conditions, etc. Energy efficiency and added value of biomethane are largely influenced by the site conditions and the neighboring infrastructures. So, how much of the natural gas used in transportation could be substituted with biomethane was examined by setting limits to the amount of organic wastes generated within urban areas. As a result, the market potential of biomethane including landfill gas was approximately 331 × 10⁶ Nm³/year, corresponding to 25% of the natural gas supply for transportation, which could be replaced by biomethane. Assuming that 2% of natural gas for transportation is replaced by biomethane, it corresponds to 29 × 10⁶ Nm³/year (approximately 9% of market potential of biomethane). However, RFS annual mixing rate may be increased upon introduction and the growth rate of the natural gas supply for transport would be higher than that of market potential of biomethane calculated in this study.     

Modeling of road traffic noise and estimated human exposure in Fulton County, Georgia, USA

Environmental noise is a major source of public complaints. Noise in the community causes physical and socio-economic effects and has been shown to be related to adverse health impacts. Noise, however, has not been actively researched in the United States compared with the European Union countries in recent years. In this research, we aimed at modeling road traffic noise and analyzing human exposure in Fulton County, Georgia, United States. We modeled road traffic noise levels using the United States Department of Transportation Federal Highway Administration Traffic Noise Model implemented in SoundPLAN?. After analyzing noise levels with raster, vector and fa?ade maps, we estimated human exposure to high noise levels. Accurate digital elevation models and building heights were derived from Light Detection And Ranging survey datasets and building footprint boundaries. Traffic datasets were collected from the Georgia Department of Transportation and the Atlanta Regional Commission. Noise level simulation was performed with 62 computers in a distributed computing environment. Finally, the noise-exposed population was calculated using geographic information system techniques. Results show that 48% of the total county population [N=870,166 residents] is potentially exposed to 55 dB(A) or higher noise levels during daytime. About 9% of the population is potentially exposed to 67 dB(A) or higher noises. At nighttime, 32% of the population is expected to be exposed to noise levels higher than 50 dB(A). This research shows that large-scale traffic noise estimation is possible with the help of various organizations. We believe that this research is a significant stepping stone for analyzing community health associated with noise exposures in the United States.     

Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons

Environmental Geochemistry and Health - Although particulate matter (PM) is composed of various chemicals, investigations regarding the toxicity that results from mixing the substances in PM are...     

Comparisons of human risk assessment models for heavy metal contamination within abandoned metal mine areas in Korea

Environmental Geochemistry and Health - This study was initiated to develop a model specialized to conduct human risk assessments (HRAs) of abandoned metal mine areas in Korea. The Korean guideline...