Quality standards of activated carbon for gas-phase applications have been deleted from the Korean national standard list since 2007, and the iodine adsorption test is the only measure currently used for quality assurance. This study was performed to propose a suitable test method and a quality standard for gas-phase activated carbon. The "1/2 saturated vapor adsorption" test has been developed as a simple and convenient method to determine the adsorption capacity of activated carbon. In this study, the developed test method was evaluated using model VOCs including toluene, methyl ethyl ketone (MEK), and ethyl acetate (EA). A virgin activated carbon revealed adsorption capacities of 344mg/g, 322mg/g, and 328mg/g for toluene, EA, and MEK, respectively, and the adsorption capacity for a mixture of the three VOCs was 334 mg/g. When a regenerated activated carbon was applied, the adsorption capacities dramatically decreased to 62 mg/g, 52 mg/g, and 61 mg/ g for toluene, EA, and MEK, respectively. In addition, the 1/2 solvent vapor adsorption tests using 13 different specimens of activated carbon showed that their capacities were closely related to the iodine adsorption numbers, and this study suggested the adsorption capacity of 300 mg/g as a new quality standard. The novel test method and its standard may help to guarantee the quality of gas-phase activated carbon used for VOCs abatement processes.

This study was performed to investigate the effects of water molecules on ozone oxidation of acetaldehyde using a manganese oxide catalyst at room temperature. The catalytic ozone oxidation was conducted at different relative humidity (RH) conditions of 0%, 50%, and 80%. As the RH increased, both ozone and acetaldehyde removal efficiencies dropped due to competitive adsorption on the surface of the catalyst. At the highest RH of 80%, the oxidation reaction was severely retarded, and oxidation by-products such as acetic acid were formed and adsorbed on the surface. After the ozone oxidation of acetaldehyde, the regeneration of the catalyst using ozone alone was tested, and the further oxidation of accumulated organic compounds was investigated under the RH conditions of 0%, 50%, and 80%. When the highest relative humidity was introduced in the regeneration step, the ozonation reaction with the by-products adsorbed on the catalyst surface decreased due to the competitive reaction with water molecules. These findings revealed that, only when relative humidity was low to minimize the formation of by-products, the ozone oxidation of acetaldehyde using the manganese oxide catalyst at room temperature can be feasible as an effective control method.

In this study, a manganese catalyst on the surface of a ceramic support was developed for the removal of odor emitted from barbecuing restaurants. Its ozone oxidation at room temperature was tested using acetaldehyde (CH3CHO), the most dominant compound in the barbecuing odor, and the ozonation efficiency under wet conditions was also studied. The manganese catalyst was made with the honeycomb-type ceramic support, and an acid pretreatment was applied to increase its specific surface area, resulting in an increase of the degree of dispersion of manganese oxide. The acetaldehyde removal efficiency using the manganese catalyst on the acidpretreated support (Mn/APS) increased by 49%, and the ozone decomposition rate and the CO2 conversion rate also increased by 41% and 27%, respectively. The catalyst without surface pretreatment (Mn/S) showed a low efficiency for the acetaldehyde ozonation, and other organic compounds such as acetic acid (CH3COOH) and nonanal (CH3(CH3)7CHO) were found as oxidation by-products. In comparison, CO2 was the most dominant product by the ozonation of acetaldehyde using the Mn/APS. When the relative humidity was increased to 50% in the influent gas stream, the acetaldehyde removal efficiency using the Mn/APS decreased, but only the production rates of CO2 and acetic acid were changed. As a result, the manganese oxide catalyst on the surface of the acid-pretreated honeycomb support manifested high acetaldehyde ozonation even at humid and room temperature conditions.

The objective of this study is to identify the emission characteristics of VOCs from small-scale painting facilities, such emissions being pollutants that impact nearby living areas and to devise improvement measures to enhance management plans regarding pollutant emissions from painting facilities. VOCs emissions from painting facilities were estimated according to Clean Air Policy Support System (CAPSS) data based on the National Institute of Environmental Research (NIER)'s emission list in 2017. Three automotive painting facilities in Seoul were chosen for evaluation of the adsorption system. We analyzed the characteristics of VOCs generated by type of different operation and measured the removal efficiency of the adsorption system. Therefore, we analyzed current emissions of VOCs from automotive painting facilities based on field measurements. According to such detailed analysis, a systematic management plan was proposed.

Indoor air contaminated with various pollutants commonly poses a risk to human health, and the need for installing air purifiers has been increasing. However, in commercial air purifiers pollutants-removal efficiency and durability are generally low. Since silver nano-composites are known to have catalytic oxidation and antibacterial capacities, it was anticipated to be applicable for indoor air purifiers. In this study, silver nano-composites were applied to granular activated carbon and scrubber solutions to treat a mixture of three air pollutants including toluene, formaldehyde, and bioaerosol. In the activated carbon deposited with silver nano-particles, the specific surface area decreased, resulting in a 10% loss of adsorption capacity for toluene. However, the removal efficacy of formaldehyde and bioaerosol increased by 10% due to the catalytic oxidation and antibacterial capacities. In the scrubber operation with silver nano-particles, the removal rates of formaldehyde and bioaerosol improved by 20%, while toluene removal was not observed. When the activated carbon column and the scrubber was connected in series, toluene was mainly removed by the activated carbon, and the removal rates of formaldehyde and bioaerosol increased in the presence of silver nano-particles. Consequently, for the improvement of indoor air quality, it is deemed appropriate to apply silver nano-material to indoor environments contaminated with pollutant mixtures.

Odor emitted from the degradation process of food waste is a common cause of public complaints, and appropriate odor treatment methods need to be implemented. In this study, a hybrid plasma catalyst system was applied to treat individual odorous compounds including acetaldehyde and hydrogen sulfide, which are known to be major odor compounds produced from food waste. MnOx catalysts were prepared by varying Mn/support loading ratios, and surface analyses showed that the Mn_5% catalyst achieved the highest performance because dominant manganese oxide species on the surface of the catalyst was found to be Mn2O3, Using the catalyst, the removal rate of hydrogen sulfide steadily increased as the space velocity in the MnOx catalyst reactor decreased. Meanwhile, the removal rate of acetaldehyde did not increase significantly when decreasing the space velocity more than 24,000 hr-1. Following the catalyst experiments using the individual odorous compounds, the hybrid system was applied for testing odor treatment of actual food waste. The actual food waste study showed that both hydrogen sulfide and acetaldehyde were steadily removed; hydrogen sulfide was removed almost completely during the initial 30-minute period, while the acetaldehyde removal was started after the decrease of hydrogen sulfide. In addition, it was confirmed that the dilution-to-threshold for odor reduced from 2,080 D/T to 300 D/T during the initial period. In conclusion, the plasma and Mn2O3 catalyst system can be applied in food waste collection containers to effectively control odor problems.

Odor emitted from food waste is commonly known as a severe problem, and needs to be controlled to minimize public complaints against food waste collection systems. In this study, ozone oxidation with manganese oxide catalyst, which is known to effectively treat odorous substances at room temperature, was applied to remove acetaldehyde and hydrogen sulfide, the model odorous compounds from food waste. In addition, the effect of relative humidity (RH) on the ozone/catalyst oxidation was tested at 40%, 60%, and 80%. When the catalyst was not applied, the removal of acetaldehyde was not observed with the ozone oxidation alone. In addition, hydrogen sulfide was slowly oxidized without a clear relationship under RH conditions. Meanwhile, the ozone oxidation rates for acetaldehyde and hydrogen sulfide substantially increased in the presence of the catalyst, but the removal efficiencies for both compounds decreased with increasing RH. Under the high RH conditions, active oxygen radicals, which were generated by ozone decomposition on the surface of the catalyst, were presumably absorbed and reacted with moisture, and the decomposition rate of the odorous compounds might be limited. Consequently, when the ozone oxidation device with a catalyst was applied to control odor from food waste, RH must be taken into account to determine the removal rates of target compounds. Moreover, its effect on the system performance must be carefully evaluated.

To abate the problem of odor from restaurants, a hybrid adsorbent consisting of organic and inorganic materials was developed and evaluated using acetaldehyde as a model compound was deveioped and evaluated. Powders of activated carbon, bentonite, and calcium hydroxide were mixed and calcinated to form adsorbent structure. The surface area of the hybrid adsorbent was smaller than that of high-quality activated carbon, but its microscopic image showed that contours and pores were developed on its surface. To determine its adsorption capacity, both batch isotherm and continuous flow column experiments were performed, and these results were compared with those using commercially available activated carbon. The isotherm tests showed that the hybrid adsorbent had a capacity 40 times higher than that of the activated carbon. In addition, the column experiments revealed that breakthrough time of the hybrid adsorbent was 2.5 times longer than that of the activated carbon. These experimental results were fitted to numerical simulations by using a homogeneous surface diffusion model (HSDM); the model estimated that the hybrid adsorbent might be able to remove acetaldehyde at a concentration of 40 ppm for a 5-month period. Since various odor compounds are commonly emitted as a mixture when meat is barbecued, it is necessary to conduct a series of experiments and HSDM simulations under various conditions to obtain design parameters for a full-scale device using the hybrid adsorbent.

Acidic and basic mixtures of odorous compounds are commonly emitted from various sources, and, in an absorption process, pH conditions in the liquid phase significantly affect the performance. In this study, the effect of pH on mass transfer in a bubble column reactor was evaluated using hydrogen sulfide and ammonia as a model mixture. Their mass transfer coefficients were then calculated. Furthermore, the total mass transfer coefficients as a function of pH were evaluated, and the experimental data were fitted into an empirical equation using dimensionless numbers. The mass transfer rates of hydrogen sulfide, the non-ionic form, increased dramatically with increasing pHs, while those of ammonia were almost unchanged because of its high solubility. As a result, a favorable pH condition for less soluble compounds must be selected to achieve high absorption capacity. The total mass transfer rates, which took into account pH effects as well as all the non-ionic and ionic constituents together, were found to be from 2.2 to 2.4 × 10−3 min−1 for hydrogen sulfide and ammonia, respectively, and they were almost constant at different pHs. The empirical equations, which were derived to obtain the best fit for the total mass transfer rates, implied that a method to increase diffusivity of each compound should be applied to improve overall mass transfer. In addition, when using the empirical equation, a mass transfer coefficient at a given set of pH and operating conditions can be calculated and used to design a water scrubbing process.

Odor emission factors (OEFs) are important parameters in characterizing odor sources, understanding emission patterns, designing abatement facilities, and providing appropriate control methods. In this study, OEFs for complex odor from grit removal chambers in publicly-owned wastewater treatment plants were determined, and the major operating conditions affecting the emission factors were investigated. In the main study site of “S” wastewater treatment plant, the averaged OEFs from the grit chamber were found to be 466.2, 162.6, and 54.7 OU/m2/min in summer, spring, and winter, respectively. OEFs from two other grit chambers in different wastewater plants were independently measured for comparison, and the values were in the same range as the OEF from S-site at a 95% confidence level. Nevertheless, the OEFs could differ depending on the types of wastewater and the sizes of wastewater treatment plants. Using the multi-variable linear regression method, correlations between OEFs and operating conditions, i.e. activities, from grit chambers were statistically analyzed. The analyses showed that operating conditions, including total suspended solids, water temperature, and temperature difference between water and air, were the most significant parameters affecting the OEF. A linear equation using these three parameters was proposed to estimate the OEF, and can be used to predict an OEF for another grit chamber, without odor measurement.

The metal plating industry produces a large amount of wastewater generally containing heavy metals with various chemical compounds; as such, treating the wastewater is both an environmental and an economic challenge. A vacuum evaporation system has been developed to effectively reduce the volume of plating wastewater. However, the gas stream discharged from the distillation unit of the evaporator is often contaminated with high concentrations of odorous compounds such as ammonia and dimethyl disulfide (DMDS). In this study, a non-thermal plasma process operated in wet conditions was applied to remove the odorous compounds, and it showed high removal efficiencies of greater than 99% for ammonia and 95% for DMDS. However, the gas flowrate more substantially affected the efficiency of ammonia removal than the efficiency of DMDS removal, because the higher the gas flowrate, the shorter the contact time between the odorous compound and the mist particles in the wet plasma reactor. The analyses of the maximum removal capacity indicated that the wet non-thermal plasma system was effective for treating the odorous compounds at a loading rate of less than 20 mg/m3/min even though the lowest amount of electrical power was applied. Therefore, the wet-type non-thermal plasma system is expected alleviate to effectively abate the odor problem of the vacuum evaporator used in the treatment of plating wastewater.

Odor compounds and air-born microorganisms are simultaneously emitted from various aeration processes such as aerobic digestion, food-waste compositing, and carcass decomposition facilities that are biologically-treating wastes with high organic contents. The air streams emitted from these processes commonly contain sulfur-containing odorous compounds such as hydrogen sulfide(H2S) and bacterial bioaerosols. In this study, a wet-plasma method was applied to remove these air-born pollutants and to minimize safety issues. In addition, the effects of a gas retention time and a liquid-gas ratio were evaluated on removal efficiencies in the wet-plasma system. At the gas reaction time of 1.8 seconds and the liquid-gas ratio of 0.05 mLaq/Lg, the removal efficiency of bioaerosol was approximately 75 %, while the removal efficiency of H2S was lower than 20 %, indicating that the gaseous compound was not effectively oxidized by the plasma reaction at the low liquid addition. When the liquid-gas ratio was increased to 0.25 mLaq/Lg, the removal efficiencies of both H2S and bioaerosol increased to greater than 99 %. At the higher liquid-gas ratio, more ozone was generated by the wet-plasma reaction. The ozone generation was significantly affected by the input electrical energy, and it needed to be removed before discharged from the process.

In this study, the growth kinetics of sulfur oxidizing bacteria, Acidithiobacillus thiooxidans, and the effect of dissolved oxygen were determined in low pH conditions for the effective removal of high concentrations of hydrogen sulfide. A dual growth kinetic was applied to identify the microbial growth rate at different hydrogen sulfide and oxygen concentrations in the liquid. A modified Monod-Gompertz equation was deemed most appropriate to examine the growth kinetic parameters of A. thiooxidans. The half saturation constants of hydrogen sulfide and oxygen for the modified Monod-Gompertz equation were found to be 0.9 and 1.1 mg/L, respectively. In addition, a bioreactor model, where the Monod-Gompertz equation was modified, was applied to simulate dissolved oxygen concentrations required for the removal of hydrogen sulfide. As a result, the dissolved oxygen concentrations were 0.5, 1.0, 1.5, and 3.3 mg/L, which were necessary to remove hydrogen sulfide to less than 10 ppm at the influent concentrations of 100, 500, 1000 and 3000 ppm, respectively. The required minimum dissolved oxygen concentrations under various conditions including reactor volume, gas retention time, and microbial concentrations can be determined using the numerical model developed in this study.

Odorous compounds produced from blackwater commonly cause domestic nuisance complaints. In this study, aseries of experiments was conducted to apply an electrolytic oxidation system to abate the odor problems fromblackwater. The electrolytic process removes odorous compounds from the liquid sources using direct and indirectoxidation; therefore, the system performance mainly relies on electrode materials. Four different electrodematerials, SS304, SS316, Ti, Ti/IrO₂, were applied, and the electrolytic oxidation showed that hydrogen sulfideand organic constituents were effectively removed. However, the weights of electrodes, SS304 and SS316, weredecreased by 7.5~8% due to the electrochemical decomposition from the anode surface. In order to improve thedurability and economical feasibility, SS304 was used as the cathode while Ti/IrO₂ was used as the anode. Theelectrode combination with the different materials (Ti/IrO₂:SS304) showed the same odor removal efficiency asthat using the same material (Ti/IrO₂:Ti/IrO₂). Consequentially, the electrolytic reaction to oxidize odorous andorganic constituents in humane manure was strongly affected by the electrode materials, and its combination needsto be carefully selected to achieve better performance.

도시지역 합류식 하수배제 설비인 우수받이 및 하수관거, 정화조 등에는 유기성 고형 물이 퇴적되기 쉬우며, 유기성 퇴적물이 부패되는 과정에서 고농도의 황계열 악취물질이 발생한다. 본 연구에서는 전기산화방식을 이용하여 유기성 퇴적물 내에 용존된 악취물질 및 전구물질을 저감시켜, 하수관거에서 기상으로 배출되는 악취 문제를 해결하고자 하였다. 실험실 규모의 밀폐된 회분식 반응기에 하수슬러지(COD 기준 8,000 ~ 28,000 mg·L-1)를 투입하고, 발생되는 악취물질 농도와 악취발생특성을 조사하였다. 여기에 전기산화시스템 을 적용하여 황계열 악취물질과 전체 유기물의 산화 및 분해실험을 진행하였다. 전기산 화 실험을 진행한 결과, 밀폐된 반응기의 기상에서 450 ppm의 고농도로 발생한 황화수 소가 반응 30분 이내에 검출한계 이하까지 제거되었으며, 메틸머켑탄과 디메틸설파이드 는 85% 이상 제거되었다. 투입된 전기에너지당 황계열 악취물질의 제거율은 최대 0.33 mg-S·kJ-1로 나타났다. 또한 1시간의 반응기간 동안 회분식 반응기 내에서 황계열 악취물 질 뿐만 아니라 고농도 퇴적물에 함유된 전체 유기물 농도가 56% 감소하여, 전기산화시 스템이 악취를 유발하는 유기성 전구물질을 동시에 저감하는 효과를 나타내었다. 결과적 으로 최소한의 전기에너지를 이용하여 하수관거 퇴적 유기물에 의한 악취문제를 해결할 수 있을 것으로 기대된다

Bioaerosols become a more noticed and important problem in indoor air quality (IAQ) control. In this study, we investigated antibacterial effects of silver nano-particles on Escherichia coli, the common Gram negative bacteria and Staphylococcus aureus, the well-mown Gram positive bacteria under aerosol conditions. The bioaerosols containing each bacterial culture were contacted with silver nano-particles sprayed in a closed chamber. Experimental results showed that the silver nano-particles had strong antibacterial activity against E. coli and S. aureus, respectively. As anticipated, high antibacterial activity was found at a high silver concentration and a long the contact time. It was also found that the bactericidal rate decreased with time due to the aggregation of silver nano-particles. Overall, the experimental finding suggested that silver nano-particles could be successfully applied to improve indoor air quality.

음식물류 폐기물은 함수율과 유기물 함량이 높은 것으로 알려져 있으며, 유기물의 분해과정에서 CO2와 H2O가 생성되어 침출수가 발생하는 것으로 알려져 있다. 이로 인해 음식물류 폐기물의 수거 및 처리과정에서 침출수에 의한 오염과 침출수 처리에 관한 문제가 증가하는 경향을 보이고 있다. 그러므로 배출지에 따라 변화하는 음식물류 폐기물의 조성과 부패기간에 따른 침출수의 발생 특성을 확인하고 그에 따른 침출수 처리방안에 대한 연구가 필요한 실정이다. 음식물류 폐기물의 경우 조성이 다양하며 그로인해 침출수의 누적발생량과 pH 변화량 또한 배출지별로 많은 차이가 생길 것으로 판단되었다. 본 연구에서는 침출수의 발생특성을 확인하기 위하여 인위적으로 조성비율이 다른 음식물류 폐기물을 제조하였으며, 환경부에서 고시한 “음식물 찌꺼기 표준시료”를 참고하여 제조한 환경부 고시 참고 시료와 단백질이 주성분인 어육류로만 제조한 어육류 단일시료, 단백질 함유량이 적은 채소와 곡류로만 제조한 채소･곡류 혼합시료를 제조하여 실험을 진행하였다. 제조 음식물류 폐기물은 곡류, 채소류, 과일류, 어육류로 구성되었으며, 함수율(80%)과 염분(4%)을 조절하여 제조하였다. 각자 비율에 맞게 제조를 완료한 시료는 일정한 온도에서 부패를 진행하였으며, 부패기간에 따른 침출수의 누적발생량과 pH 변화를 측정하였다. 부패가 진행되는 과정에서 24시간 간격으로 침출수의 누적발생량과 pH 변화량을 관찰하였다. 실험결과 표준적인 조성비율을 가진 환경부 고시 참고 시료의 경우 보다 극단적인 조성비율을 가지는 시료의 경우 부패가 빠르게 진행되는 것을 확인하였다. 어육류 단일시료의 경우 4일 후 120 mL/kg의 침출수가 발생하였으며, 환경부 고시 참고 시료의 경우 –20 mL/kg으로 오히려 처음에 비해 감소하는 경향을 보였다. 또한 pH 측정결과 환경부 고시 참고 시료와 채소･곡류 혼합시료의 경우 5.0에서 3.5까지 감소하는 경향을 보였지만 어육류 단일시료의 경우 5.8에서 6.5까지 증가하였다. 위 결과를 통해 배출지의 음식물류 폐기물의 조성 및 부패기간에 따른 침출수 처리장치 및 관리방안의 기초설계 인자를 도출하고자 하였다.