• Advances in environmental research
• /
• v.7 no.2
• /
• pp.73-85
• /
• 2018

The anaerobically digestion and agricultural application of organic wastes was conducted using food wastes and cow dung. Twenty kilograms each of the feed stocks was added into two 30 liters-capacity batch digesters. The anaerobic digestion was carried out within a temperature range of $25-31^{\circ}C$ for a retention time of 51 days. The results showed a cumulative gas yield of 5.0 bars for food waste and no gas production for cow dung within the retention time. Bacteria such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris and Clostridium sp were isolated. Fungi isolated included Aspergillus niger, Aspergillus nidulan, Trichophyton rubrum and Epidermophyton flocossum. The non-dispersive infrared (NDIR) analysis of the biogas produced confirmed that the gas consisted of $CH_4$, $CO_2$ and $H_2$. Statistical analysis revealed there was no significant correlation between temperature and biogas produced from the organic wastes (r= 0.177, p = 0.483).The organic wastes from the biogas production process stimulated maize growth when compared to control (soil without organic waste) and indicated maximum height. The study therefore reveals that food waste as potential substrates for biogas production has a moderate bio-fertilizer potential for improving plant growth and yield when added to soil.

• Korean Journal of Food Science and Technology
• /
• v.17 no.5
• /
• pp.406-408
• /
• 1985

n-Hexanal in headspace over the cooked brown rice stored at $5^{\circ}C$ and $35^{\circ}C$ for 0. 4, 8 and 12 months was determined by a modified direct vapor injection gas chromatographic method. The retention time of n-hexanal was 3.5 min and n-hexanal could be rapidly separated from other compounds at the operational conditions of gas chromatography. n-Hexanal contents of cooked brown rice also showed a standard deviation of less than 10% of the average.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.11
• /
• pp.1809-1818
• /
• 2008

Biotechnological treatment of sulfate- and metal-ions-containing acidic wastewaters from mining and metallurgical activities utilizes sulfate-reducing bacteria to produce sulfide that can subsequently precipitate metal ions. Reducing sulfate at a low pH has several advantages above neutrophilic sulfate reduction. This study describes the effect of sulfide removal on the reactor performance and microbial community in a high-rate sulfidogenic gas-lift bioreactor fed with hydrogen at a controlled internal pH of 5. Under sulfide removal conditions, 99% of the sulfate was converted at a hydraulic retention time of 24 h, reaching a volumetric activity as high as 51 mmol sulfate/l/d. Under nonsulfide removal conditions, <25% of the sulfate was converted at a hydraulic retention time of 24 h reaching volumetric activities of <13 mmol sulfate/l/d. The absence of sulfide removal at a hydraulic retention time of 24 h resulted in an average $H_2S$ concentration of 18.2 mM (584 mg S/I). The incomplete sulfate removal was probably due to sulfide inhibition. Molecular phylogenetic analysis identified 11 separate 16S rRNA bands under sulfide stripping conditions, whereas under nonsulfide removal conditions only 4 separate 16S rRNA bands were found. This shows that a less diverse population was found in the presence of a high sulfide concentration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.7
• /
• pp.394-399
• /
• 2016

The silicon dioxide ($SiO_2$) was deposited using various gas as oxygen and nitrous oxide ($N_2O$) in nowadays. In order to improve electrical characteristics and the interface state density ($D_{it}$) in low temperature, It was deposited with carbon dioxide ($CO_2$) and silane ($SiH_4$) gas by inductively coupled plasma chemical vapor deposition (ICP-CVD). Each $D_{it}$ of $SiO_2$ using $CO_2$ and $N_2O$ gas was $1.30{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$ and $3.31{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$. It showed $SiO_2$ using $CO_2$ gas was about 2.55 times better than $N_2O$ gas. After 10 years when the thin film was applied to metal/insulator/semiconductor(MIS)-nonvolatile memory(NVM), MIS NVM using $SiO_2$($CO_2$) on tunneling layer had window memory of 2.16 V with 60% retention at bias voltage from +16 V to -19 V. However, MIS NVM applied $SiO_2$($N_2O$) to tunneling layer had 2.48 V with 61% retention at bias voltage from +20 V to -24 V. The results show $SiO_2$ using $CO_2$ decrease the $D_{it}$ and it improves the operating voltage.

• Applied Chemistry for Engineering
• /
• v.18 no.2
• /
• pp.162-167
• /
• 2007

Hydrogen production and its dynamics were investigated in the continuous anaerobic digestion process using Clostridium beijerinckii Donker 1926. In this work, glucose was used as a substrate and hydraulic retention times (HRT) were 0.5, 0.25 or 0.125 day. The removal efficiency of carbohydrate was over 99% under all of HRT conditions. As HRT was shorter, COD removal efficiency became lower while hydrogen content in the total gas and hydrogen production rate became higher. The cell growth yield and hydrogen production yield were 0.27 g-VSS/g-glucose and 0.26 L/g-glucose, respectively, at the steady state. It is expected that the microorganism is able to produce hydrogen when used in the wastewater treatment containing carbohydrate such as glucose. Also, the results in this study could be applied to the actual hydrogen gas production, a promising alternative energy.

• Geomechanics and Engineering
• /
• v.33 no.2
• /
• pp.141-154
• /
• 2023

This study investigated the effect of water retention characteristics between aged and fresh Municipal Solid Waste (MSW) on the stability of the landfill. A series of transient numerical modeling for the slope of an MSW landfill was performed considering the variation of water retention characteristics due to leachate circulation. Four different scenarios were considered in this analysis depending on how to obtain hydraulic conductivity and the aging degree of materials. Unsaturated hydraulic properties of the MSW used for the modeling were evaluated through modified hanging column tests. Different water retention properties and various landfill conditions, such as subgrade stiffness, leachate injection frequency, and gas and leachate collection system, were considered to investigate the pore water distribution and slope stability. The stability analyses related to the factor of safety showed that unsaturated properties under those varied conditions significantly impacted the slope stability, where the factor of safety decreased, ranging between 9.4 and 22%. The aged materials resulted in a higher factor of safety than fresh materials; however, after 1000 days, the factor of safety decreased by around 10.6% due to pore pressure buildup. The analysis results indicated that using fresh materials yielded higher factor of safety values. The landfill subgrade was found to have a significant impact on the factor of safety, which resulted in an average of 34% lower factor of safety in soft subgrades. The results also revealed that a failed leachate collection system (e.g., clogging) could result in landfill failure (factor of safety < 1) after around 298 days, while the leachate recirculation frequency has no critical impact on stability. In addition, the accumulation of gas pressure within the waste body resulted in factor of safety reductions as high as 24%. It is essential to consider factors related to the unsaturated hydraulic properties in designing a landfill to prevent landfill instability.

• Journal of the Korean Chemical Society
• /
• v.42 no.6
• /
• pp.646-651
• /
• 1998

The molecular structure of sulfur compounds and the retention relationship are studied by gas chromatography. Analyzed sulfur compounds are, hydrogen sulfide, sulfur dioxide, carbon disulfide, ethyl mercaptan, dimethyl sulfide, iso-propyl mercaptan, normal propyl mercaptan, ethyl methyl sulfide, tert-butyl mercaptan, tetrahydrothiophene, thiophene, and 2-chlorothiophene. Multiple linear regression explains the retention relationship of molecular descriptors. In GC the temperature program is 30$^{\circ}C$ held for 10.5 min, and then increased to 150$^{\circ}C$ at a rate 15$^{\circ}C$/min. Predicted equation for relative retention time (RRT) using SAS program is as follows; $RRT=0.121bp+14.39dp-8.94dp^2+0.0741sqmw-35.78\; (N=8,\; R^2=0.989, \;Variance=0.175,\;F=66.21)$. RRTs are function of boiling point, the square root of molecular weight, molecular dipole moment, and boiling point effects mostly on RRT. The RRT is maximized at the molecular dipole moment of 0.805D, when using nonpolar columns. The planar and highly symmetric compounds are eluted slowly. The square, of correlation coefficient $(R^2)$ using SAS program, is 0.989, and the variance is 0.175 in training sets. For three sulfur compounds, the variance between observed RRTs and predicted RRTs is 0.432 in testing sets.

• Culinary science and hospitality research
• /
• v.18 no.4
• /
• pp.266-276
• /
• 2012

Salt, one of the main ingredients to make bread, functions differently according to environmental changes such as usage levels and methods. We examined the effects of yeast soaking time in about 8% salt solution on gas production and fermentation rate of dough and characteristics of white bread. Gas retention, related to gas production and fermentation rate, was the best at the 45 min soaking time. And pH of dough was appropriate to the fermentation in the range of 15 to 45 min of soaking time. Volume and specific volume of bread were best in 45 min soaking time(p<0.001), but the hardness of crumb texture analyzed with TA was the hardest among the samples(p<0.001). Brightness of color(L value) was significantly affected by soaking time(p<0.001), but b value was not considered. According to the preference test, the white pan bread made with 45 min soaking time in salt solution was preferred the most.

• Korean Journal of Food Science and Technology
• /
• v.32 no.5
• /
• pp.997-1001
• /
• 2000

The organic acids in 3 kinds of medicinal herbal extracts were screened and compared each other according to their organic acid contents by an efficient gas chromatographic method. It involves solid-phase extraction of organic acids using Chromosorb P with subsequent conversion to stable tert-butyldimethysilyl derivatives for the direct analysis by capillary column gas chromatography and gas chromatography-mass spectrometry. Total of 24 organic acids were reproducibly identified from 3 kinds of herbal extracts. When the GC profiles were simplified to their retention index spectra, characteristic patterns were obtained for each herb sample. As expected, three kinds of herbal extracts showed three distinct patterns.

• Korean Journal of Food Science and Technology
• /
• v.28 no.6
• /
• pp.1177-1179
• /
• 1996

A static headspace gas chromatographic (HSGC) technique was used to quantify toluene and other solvents (methanol, isopropyl alcohol, methyl ethyl ketone and ethyl acetate) in food packaging films. Comparison of retention times and coefficient variations for standard solvents showed consistent retention time and good reproducibility. Therefore, this method using static HSGC proved to be superior in rapidity and reproducibility, and is thought to be adaptable to analysis of a large number of samples. The methanol content was $N.D.\;(not\;detected){\sim}0.939\;mg/m^2$, toluene $N.D.{\sim}1.403\;mg/m^2$, melthyl ethyl ketone $N.D.{\sim}0.932\;mg/m^2$, total solvent content was $N.D.{\sim}2.433\;mg/m^2$.