• Environmental Engineering Research
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• 제15권3호
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• Journal of Microbiology and Biotechnology
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• 제8권4호
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• pp.341-346
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• 1998

Optimization for the production of Pest an was followed by the Plackett-Burman Design, using modified Czapek-dox medium as the starting point. At the flask level, $K_2HPO_4$, $MgSO_4{\cdot}7H_2O$, and aeration variables positively affected the Pestan production, DCW (dry cell weight), apparent viscosity, and flocculating activity response. KCI and $FeSO_4{\cdot}7H_2O$ negatively affected the Pestan production, DCW, apparent viscosity, and flocculating activity response. Aeration variable was shown to have a positive effect on only the flocculating activity response among Pestan production, DCW, and apparent viscosity responses. In comparison of the positive and negative variables media conditions, Pestan production and flocculating activity differed by about 9 and 125 times, respectively. In particular, at the jar fermentor level, the aeration variable was the most important factor of the all responses (pestan production, DCW, apparent viscosity, flocculating activity, and anionic charge density). The flocculating activity and apparent viscosity of Pestan were closely related to the molecular chain length and charge density.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권6호
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• pp.460-464
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• 2000

Extracellular polymeric substances (EPS) are believed to play a role in the binding and formation of microbial flocs. However, the precise role is not well known. Sludge settling characteristics and the carbohydrate to protein ratio in EPS were tested with various airflow rates in this study. Sludge was collected from three modified sequencing batch reactors (SBRs), which were operated at 16$\^{C}$ with an airflow rate of 0.8L/min, 3L/min and 6L/min, respectively. During the operation, the reactor operated at an airflow rate of 0.8L/min showed sludge volume index (SVI) of 80 to 90ml/g and a constant ratio of carbohydrate to protein in the EPS, while a significant increase in the SVI was seen in the other reactors. Sludge bulking increased the amount of carbohydrate in the EPS, while kept protein almost constant in the airflow rate of 3L/min ad 6L/min. Surface charge also increased with increases in the carbohydrate to protein ratio in the EPS, which weakens the attraction between the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was tween the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was inferred to be essential for bioflocculation.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2679-2683
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• 2014

Mechanisms underlying the impacts of interactions between carbon nanoparticles (CNPs) and ionic liquids (ILs) on the physicochemical behavior of CNPs need to be more full worked out. This manuscript describes a theoretical investigation at multiple levels on the interactions of fullerene $C_{60}$ with 21 imidazolium-based ILs of varying alkyl side chain lengths and anionic types and their impacts on $C_{60}$ dispersion behavior. Results show that ${\pi}$-cation interaction contributed to mechanism of the $C_{60}$-IL interaction more than ${\pi}$-anion interaction. The calculated interaction energy ($E_{INT}$) indicates that $C_{60}$ can form stable complex with each IL molecule. Moreover, the direction of charge transfer occurred from IL to $C_{60}$ during the $C_{60}$-IL interaction. Quantitative models were developed to evaluate the self-diffusion coefficient of $C_{60}$ ($D_{fullerene}$) in bulk ILs. Three interpretative molecular descriptors (heat of formation, $E_{INT}$, and charge) that describe the $C_{60}$-IL interactions and the alkyl side chain length were found to be determinants affecting $D_{fullerene}$.

• 한국환경보건학회지
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• 제20권4호
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• pp.60-71
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• 1994

The average volume of waste per a person in Korea is exceedingly higher than that of Europeans. But the social movement for the resources recycling and the environmental conservation makes the people play their part in several activities like the Separate Collection System. At the time of this agitation, Korean central government brought the Volume Based Waste Charge System into operation in some regions on a trial basis having full-scale operation nationwidely near at hand. Andong City which is one of points under trial operation had remarkble result during this term in resources recycling as well as wastes reducing. The wastes' diminution reached to 32.0 % and the resources recycling was increased by 13.7 times. The responses from the 701 housewives in Andong were also very stimulative. The neccesity of this system was judged conclusively by 91.6 % of total answerers. Also this system was considered as a successful one by 78.4 % popular support. But not little portion (53.8 %) of the answerers felt that the detail methods of this system were unconvenient. In order to take root this system in it's early stages, the Separate Collection should be carried out perfectly and systematically with top priority. And the next program should be the improvement of the detail methods in this system.

• 한국환경과학회지
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• 제17권12호
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• pp.1413-1419
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• 2008

The Kyoto Protocol, that had been in force from February 16, 2005, requires significant reduction in $CO_2$ emissions for all anthropogenic sources containing transportation, industrial, commercial, and residential fields, etc, and automotive emission standards for air pollutants such as particulate matter (PM) and nitrogen oxides $(NO_x)$ become more and more tight for improving ambient air quality. This paper has briefly reviewed homogeneous charge compression ignition (HCCI) combustion technology offering dramatic reduction in $CO_2,\;NO_x$ and PM emissions, compared to conventional gasoline and diesel engine vehicles, in an effort of automotive industries and their related academic activities to comply with future fuel economy legislation, e.g., $CO_2$ emission standards and corporate average fuel economy (CAFE) in the respective European Union (EU) and United States of America (USA), and to meet very stringent future automotive emission standards, e.g., Tier 2 program in USA and EURO V in EU. In addition, major challenges to the widespread use of HCCI engines in road applications are discussed in aspects of new catalytic emissions controls to remove high CO and unburned hydrocarbons from such engine-equipped vehicles.

• 한국지구과학회지
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• 제43권4호
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• pp.532-538
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• 2022

Under anoxic conditions, this study investigated removal of dissolved As(III) by Si and Al oxides including natural sand, chemically washed sand (silica), alumina, and activated alumina. Despite the similar surface area, natural sand showed greater extents of As(III) sorption than chemically washed sand. This was likely due to the high reactivity of Fe(oxyhydr)oxide impurities on the surface of natural sand. For both sands, As(III) sorption was the greatest at pH 7.1, in agreement with the weakly dissociating tendency of arsenous acid. Also, the least sorption was observed at pH 9.6. At basic pH, elevated silicate, which originated from the dissolution of silica in sands, would compete with As(III) for sorption. Due to the highest surface area, activated alumina was found to quantitatively immobilize the initially added As(III) (6.0×10^-7-2.0×10^-5 M). Alumina showed As(III) sorption compared to or greater than chemically washed sand, although the former had less than 6% of the surface of area the latter. The greater reactivity of alumina than chemically washed sand can be explained by using the shared charge of oxygen.

• 한국전산구조공학회논문집
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• 제34권6호
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• pp.355-362
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• 2021

증기운 폭발의 폭압을 예측하거나 위험성 분석을 위하여 다양한 폭압 산정법이 존재하지만 대표적으로 경험적 방법인 TNT 등가량 환산법과 멀티에너지법을 주로 사용한다. 멀티에너지법은 환경적 요인을 고려한 폭발강도계수를 사용한다. 본 연구에서는 문헌 분석을 통하여 점화원 강도를 세분하고 강도분류를 확장하여 개선한 폭발강도계수 가이드라인을 제안하였다. 개선한 폭발강도계수 가이드라인의 합리성 검증과 기존 Kinsella 가이드라인과의 비교를 위하여 실제 추정 폭압과 대조가 가능한 4가지의 증기운 폭발 사례를 적용하였다. 결과적으로 기존 Kinsella 가이드라인은 실제 추정 폭압에 비하여 광범위하거나 부정확한 폭압 산정 결과를 나타내는 것으로 확인하였다. 반면, 개선한 폭발강도계수 가이드라인은 명확한 점화원의 강도 선정이 가능하고 분류의 확장을 통하여 더욱 세분화된 계수 값의 선정이 가능함에 따라 실제 사례와 비교적 유사한 폭압 산정이 가능하다.

• 한국토양비료학회지
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• 제31권4호
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• pp.414-419
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• 1998

우리나라 논 밭 경작지 토양의 표면전하에 미치는 유기물의 기여도를 파악하기 위하여, 화강암 풍화토(사촌통, 상주통)와 석회암 풍화토(율곡통, 평전통)를 가지고, 유기물 제거 전후 토양의 표면전화 특성을 이온흡착법을 이용하여 pH 3.5~9.0 범위에서 측정하였다. 유기물 제거 여부에 관계없이 모든 토양의 표면 음전하는 실험 pH 범위 내에서 pH 증가에 따라 직선적으로 증가하였다. pH 다누이 변화량에 대한 토양 표면 음전하의 단위 변화량(dCEC/dpH)을 토양 표면전하의 pH 의존성 지표로 제안하였다. 유기물 제거후에는 0.16~1.91의 범위로 크게 낮아졌다. 자연 토양 pH 조건에서 전체 토양표면전하량 중 유기물에 의한 표면전하량의 비율은 15.0~82.4% 범위로 나타났다. 토양유기물 1%가 발현하는 토양표면전하량은 $0.22{\sim}5.03cmol^+\;kg^{-1}$로 토양별로 차이가 컸다. 토양 유기물이 dCEC/dpH에 미치는 영향은 oxalic acid 추출 산화철 함량이 많은 논토양이 밭토양에 비하여 작았다.

• 한국환경교육학회지:환경교육
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• 제14권1호
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• pp.56-65
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• 2001

The purpose of this study was to examine and compare the current status of nonformal environmental education between civil and public organization. This study utilized a survey methodology, The survey was developed by the researchers and it has 4 subscales. The subjects consisted of 28 persons who are in charge of environmental education in civil organizations and 31 persons in public organizations. Descriptive statistics provided frequencies and percents for all demographic variables and items. Based on the findings of this study, it is firstly recommended that the government support environmental education policy that prioritizes nonformal environmental education for civil and public organizations. Secondly, both civil and public organizations should make continuing efforts for better nonformal environmental education programs and come up with practical ways to improve ability and quality of the staffs in the civil and public organizations by providing systematic reeducation programs and practical guidelines that would be applied to their daily lives.