• Journal of Environmental Health Sciences
• /
• v.23 no.1
• /
• pp.105-108
• /
• 1997

For the removal of heavy metals, Cd, Cu and Cr were used. The initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 76.2-89.0% and 69.0-79.0%, respectively. The initial concentration of Cr were 1~5 ppm, and the-removal efficiency was low especially at high concentration. In general, the initial concentrations of heavy metals had no relation to the removal efficiency. At the beginning, the removal efficiency was very high, but it was maintained at constant concentration. The trends of accumulations of heavy metals in the stem increased in proportion to the initial concentration. The removal efficiency of heavy metals increased a little bit when nutrients existed in the solution. So that, the initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 84.8-91.0% and 75.9-82.0%. The initial concentration of Cr were 1-5 ppm, the removal efficiency was 25.0-67.0%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.366-366
• /
• 2010

Simulation Program (AFORS-HET 2.4.1) was used, include the basic structure of crystalline silicon thin film as above, below Intrinsic a-Si:H films bonded symmetrical structure (Symmetrical structure) were used. Efficiency with variation of the concentration was grown by the a-Si p-type with increasing concentrations of Na, efficiency with increasing a-Si n-type of Nd Concentrations was not changed, was decreased rapidly when concentrations were decreased. Efficiency was increased when c-Si n-type of Nd concentration was increased, otherwise efficiency was decreased when concentration was decreased.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.24 no.6
• /
• pp.984-989
• /
• 1995

The concentration-efficiencyh of blue dextran solution in the progressive freeze-concentration was related to the freezing conditions such as the freezing speed and the stirring speed in the solution phase. From the theoreticla balance equation of heat and mass transfer at freezing front, the relationship between the freezing conditions and the ice structure at freezing front was drived. A high freeze-concentration efficiency was obtained under the operating conditions represented by a low speed of freezing and a high speed of stirring. The operating conditions were related to a smooth solid-liquid interface and these results were well explained by the theoretical equation. Effect of the solute component size on the concentration efficiency in the progressive freezeconcentration was also tested. The concentration efficiency of latex particles showed a lower value than that of blue dextran, however, its difference was insignificant.

• Journal of Environmental Science International
• /
• v.11 no.7
• /
• pp.757-763
• /
• 2002

The objective of this study is to delineate removal efficiency of the Linear alkylbenzene sulfonates(LAS) in solution by $TiO_2$ photocatalytic oxidation as a function of the following different experimental conditions : initial concentration of LAS, $TiO_2$ concentration, UV wavelength and pH of the solution. It was increased with decreasing initial concentration of LAS and with decreasing pH of the solution. Removal efficiency increased with increasing $TiO_2$ concentration but was almost the same at $TiO_2$ concentration of 2 g/L and 3 g/L, i.e., for initial LAS concentration of 50 mg/L. It was removal efficiency was 85% at 150 min in the case of $TiO_2$ concentration of 0.5 g/L but 100% after 150 min in the case of $TiO_2$ concentration of 1 g/L, 100% after 110 min in the case of $TiO_2$ concentration of 2 g/L and 3 g/L. UV wavelength affection on the removal efficiency of LAS decreased in the order of 254, 312 and 365 nm as increasing wavelength. But the removal efficiency of LAS was nearly the same at UV wavelength of 254 nm and 312 nm.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.347-350
• /
• 2002

The petrochemical products can cause soil and groundwater contamination during their transportation and the use of the products, and while being contained in underground storage tanks(USTs) throughout the leakage. To treat the contaminated soil, the bioventing method is suitable for the remediation of semi-volatile compounds, such as diesel and kerosene. Biofiltration is one of possible method to treat the off-gas produced in the process of the bioventing. This study is related to the usage, effectiveness of treatment, and feasibility of two types of biofilter system made of ceramic-compost and polymer respectively to treat diesel VOCs at constant retention time of 20 sec. Compost biofilter showed the average removal efficiency of 73 % when the inlet concentration increased to 20 ppmv. Increased the inlet concentration decreased the microbial activities as well as the removal efficiency. On the contrary, the removal efficiency of the polyurethane biofilter was maintained at 88 % at the inlet concentration of 13 ppmv during ten days and was obtained to 80 % at the inlet concentration of 30 ppmv in spite of the drop of the efficiency in the sudden increase of the inlet concentration. At the beginning of the experiment it showed low removal efficiency at low inlet concentration due to the low microbial activity, however, as experiments proceed the removal efficiency could be obtained more than 80% at high inlet concentration.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.5
• /
• pp.747-753
• /
• 2006

Air flotation is a solid-liquid separation process that utilizes up-flow microbubbles to thicken activated sludge and enhance clarification efficiency. Continuous air flotation experiments were performed to investigate the effect of operation parameters such as initial MLSS (mixed liquor suspended solid) concentration, air pressure, surface loading rate, air to solid (A/S) ratio, and flotation time on thickening efficiency. An initial activated sludge concentration ranged from 3,000 to 12,000mgSS/L and thickened sludge concentration varied from 6,400 to 28,100mgSS/L. The result showed that the thickening efficiency was mainly dependent on surface loading rate, A/S ratio, and flotation time. The pressure did not affect the thickening efficiency when it kept in the range of 1.6 to 1.8 bar. Experimental results showed that the thickening efficiency of activated sludge was increased only when the feed sludge concentration exceeded 5,000mgSS/L and the thickened concentration was over 20,000mgSS/L. At this time, SS concentration in the clarified liquid was ranged from 5 to 10mg/L.

• Journal of Korean Society of Water and Wastewater
• /
• v.11 no.1
• /
• pp.64-73
• /
• 1997

Most of the municipal wastewater treatment plants operated in Korea are designed for high concentrations municipal sewage. However, activated sludge process employed by municipal wastewater treatment plant is operated at low organic loading. The objective of this study was to determine optimum operating condition of activated sludge process for treatment of low concentration municipal sewage. Three bench scale activated sludge reactors were operated to investigate the effect of HRT and SRT on the COD and TSS removal efficiency. The average concentration of TSS, SCOD, SBOD and TKN in influent were 118mg/l, 61mg/l, 21mg/l, and 12mg/l, respectively. The activated sludge reactors operated with various HRT and SRT showed about 89-93% TSS removal efficiency. HRT and SRT does not affect the TSS removal efficiency of actvatied sludge process significantly. However, HRT affected the SCOD removal efficiency slightly. As the HRT decreases from 13hours to 3hours, the SCOD removal efficiency decreases from 67% to 56%. The average effluent TCOD concentration of the reactor operated with 3hours of HRT was approximatly 40-45mg/l. Kinetic coefficient yield (Yt) and decay coefficients(Kd) were 0.594-0.954 mgMLVSS/mgCOD and $0.0197-0.0317day^{-1}$, respectively. Low concentration municipal sewage can be treated with 3 hours of HRT without effluent quality deterioration and SRT does not affect the substrate removal efficiency at this operation condition.

• Journal of Radiation Industry
• /
• v.17 no.4
• /
• pp.471-479
• /
• 2023

In In-situ radioactivity measurement techniques, efficiency calibration models use predefined models to simulate a sample's geometry and radioactivity distribution. However, simplified efficiency calibration models lead to uncertainties in the efficiency curves, which in turn affect the radioactivity concentration results. This study aims to develop an efficiency calibration optimization methodology to improve the accuracy of in-situ gamma radiation measurements for byproducts from industrial facilities. To accomplish the objective, a drive mechanism for rotational measurement of an byproduct simulator and a sample was constructed. Using ISOCS, an efficiency calibration model of the designed object was generated. Then, the sensitivity analysis of the efficiency calibration model was performed, and the efficiency curve of the efficiency calibration model was optimized using the sensitivity analysis results. Finally, the radiation concentration of the simulated subject was estimated, compared, and evaluated with the designed certification value. For the sensitivity assessment of the influencing factors of the efficiency calibration model, the ISOCS Uncertainty Estimator was used for the horizontal and vertical size and density of the measured object. The standard deviation of the measurement efficiency as a function of the longitudinal size and density of the efficiency calibration model decreased with increasing energy region. When using the optimized efficiency calibration model, the measurement efficiency using IUE was improved compared to the measurement efficiency using ISOCS at the energy of ²²⁸Ac (911 keV) for the nuclide under analysis. Using the ISOCS efficiency calibration method, the difference between the measured radiation concentration and the design value for each simulated subject measurement direction was 4.1% (1% to 10%) on average. The difference between the estimated radioactivity concentration and the design value was 3.6% (1~8%) on average when using the ISOCS IUE efficiency calibration method, which was closer to the design value than the efficiency calibration method using ISOCS. In other words, the estimated radioactivity concentration using the optimized efficiency curve was similar to the designed radioactivity concentration. The results of this study can be utilized as the main basis for the development of regulatory technologies for the treatment and disposal of waste generated during the operation, maintenance, and facility replacement of domestic byproduct generation facilities.

• Membrane and Water Treatment
• /
• v.11 no.3
• /
• pp.217-222
• /
• 2020

An electrochemical oxidation process was applied to remove cyanide (CN^-) from real plating wastewater. CN^- removal efficiencies were investigated under various operating factors: current density and electrolyte concentration. Electrolyte concentration positively affected the removal of both CN^- and Chemical Oxygen Demand (COD). As the electrolyte concentration increased from 302 to 2,077 mg Cl^-/L, removal efficiency of CN^- and COD increased from 49.07% to 98.30% and from 23.53% to 49.50%, respectively, at 10 mA/㎠. Current density affected the removal efficiency in a different way. As current density increased at a fixed electrolyte concentration, CN^- removal efficiency increased while COD removal efficiency decreased, this is probably due to lowered current efficiency caused by water electrolysis.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.194-197
• /
• 2008

We measured the efficiency and flue gas concentration of a 90kW woodchip boiler which is for heating water of lodging. At nominal operating condition, the fuel, woodchip is fed into the boiler at a rate of 22.6 kg/h. In order to determine the efficiency of the boiler, we measured the water flow rate, woodchip flow rate, heating value and water content of woodchip, temperature of inlet and outlet of heating water. The results of test show that the power output of the woodchip boiler is 90.0 kW(77,400 kcal/h) and the thermal efficiency of the boiler is 88.5%. By using a gas analyser, flue gas concentrations are measured. The results show that O2 in the flue gas is 10.2%, CO concentration is 393 ppm and NOx concentration is 74 ppm.