• Journal of Environmental Science International
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• v.15 no.7
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.488-493
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• 2004

The effects were examined from several conditions of $TiO_2$ photocatalysis reaction to phenols degradation by changing it's reacting conditions such as phenol concentration, pH, $TiO_2$ concentration, $H_2O_2$ concentration, flow rate, and intensity of ultraviolet rays. Phenol degradation was more efficient in low concentration of phenol, neutral pH. Phenol degradation appeared to increase as concentration of $TiO_2$ photocatalyst, that of $H_2O_2$ and intensity of ultraviolet rays increased. As $TiO_2$ dosage increased, initial rate constant k linearly increased. When $H_2O_2$ was injected more than optimum, phenol removal rate didn't increase in proportional to the change of $H_2O_2$ concentration as OH radicals was being consumed. When flow rate is less than $4.75m^3/m^2$ day, phenol removal efficiency appeared to decrease as ultraviolet rays transmission rate becomes low by $TiO_2$ suspension coated in photo reaction column. Meanwhile, initial rate constant according to light intensity change in less than $25mW/cm^2$ appeared to be in proportion to light intensity ($mW/cm^2$) Removal efficiency decreased about 12% after 180 minutes of reaction time while showed stable removal efficiency of 100% after 300 minutes when using regenerated $TiO_2$.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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• pp.256-262
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• 2005

The purpose of this study is to investigate the performances of organic removal and methane recovery by using a full scale two-phase anaerobic system. The full scale two-phase anaerobic process was consists of an acidogenic anaerobic baffled reactor (ABR) and a methanognic upflow anaerobic sludge blanket (UASB) reactor. The volumes of acidogenic and methanogenic reactors were designed to $28.3m^3$ and $75.3m^3$. The two-phase anaerobic system represented 60-82% of COD removal efficiency when the influent COD concentration was in the range of 7,150 to 16,270 mg/L after screening (average concentration is 10,280 mg/L). After steady-state, the effluent COD concentration in the methanogenic reactor showed $2,740{\pm}330 mg/L$ by representing average COD removal efficiency was $71.4{\pm}8.1%$ when the operating temperature was in the range of $19-32^{\circ}C$. The effluent SCOD concentration was in the range of 2,000-3,000 mg/L at the steady state while the volatile fatty acid concentration was not detected in the effluent. Meanwhile, the COD removal efficiency in the acidogenic reactor showed less than 5%. The acidogenic reactor played key roles to reduce a shock-loading when periodic shock loading was applied and to acidify influent organics. Due to the high concentration of alkalinity and high pH in the effluent of the methanogenic reactor, over 80% of methane in the biogas was produced consistently. More than 70% of methane was recovered from theoretical methane production of TCOD removed in this research. The produced gas can be directly used as a heat source to increase the reactor temperature.

• Journal of Environmental Health Sciences
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• v.38 no.6
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• pp.568-574
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• 2012

Objectives: The purpose of this experiment is to understand the phosphorus removal ratio effects of iron plates per unit of surface area through the iron electrolysis system, which consists of an anoxic basin, aerobic basin, and iron precipitation apparatus. Methods: Iron electrolysis, which uses an iron precipitation reactor in anoxic and oxic basins, consisted of iron plates with total areas of 400 $cm^2$, 300 $cm^2$ and 200 $cm^2$ respectively. The FNR process was operated with a hydraulic retention time and a sludge retention time of 12 hours and three days, respectively. Wastewater used in the experiments was prepared by dissolving $KH_2PO_4$ in influent water. Results: The iron plates 400 $cm^2$ (16.6 $mA/cm^2$), 300 $cm^2$ (13.3 $mA/cm^2$) and 200 $cm^2$ (7.3 $mA/cm^2$) in surface area in the phosphorus reactor had respective phosphorus of 2.4 mg/l, 2.7 mg/l and 3.2 mg/l in the effluent and phosphorus removal respective efficiencies of 90.3%, 89.1% and 87.1%. The effluent in the reactor, where the iron plate was not used, had relatively very low phosphorus removal efficiency showing phosphorus concentration of 15.3 mg/l and a phosphorus removal efficiency about 38.3%. Phosphorus removal per ferrous was 0.472 mgP/mgFe in the iron electrolysis system where the surface area of iron was low. Phosphorus pollution load per active surface area and the phosphorus removal efficiency had an interrelation of RE = -0.27LS + 89.0 (r = 0.85). Conclusion: With larger iron plate surface area, the elution of iron concentration and phosphorus removal efficiency was higher. The removal efficiency of phosphorus has decreased by increasing the initial phosphate concentration in the iron electrodes. This shows a tendency of decreasing phosphorus removal efficiency because of decreasing of iron deposition as the phosphorus pollution load per active surface area increases.

• Environmental Engineering Research
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• v.15 no.4
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• pp.215-223
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• 2010

This study attempted to develop and suggest a more appropriate method for the determination of event mean concentration (EMC) and pollutant removal efficiency of a stormwater best management practice (BMP) considering rainfall. The stormwater runoff and hydrologic data gathered from 22 storm events during a 28-month monitoring period on a swirl and filtration type of BMP were used to evaluate the developed methods. Based on the findings, the modified EMC method resulted in lower (average) values than the overall EMC, although the differences were not significant (P>0.05). By comparison, the developed 'Rainfall Occurrence Ratio' (ROR) method was most significantly correlated (r=0.967 to 988, P<0.009) with the other existing removal efficiency determination methods such as the 'Efficiency Ratio' (ER), 'Summation of Loads' (SOL) and 'Regression of Loads' (ROL) methods. In addition, the ROR method gave the highest efficiency values, with no significant differences with any of the pollutant parameters, unlike the other three methods. These results were obtained because the ROR method integrated both pollutant loading and rainfall, which are not considered by the other three methods. Therefore, this study proved the suitability of the modified EMC and ROR methods for application in other BMP monitoring studies.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.58-66
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• 2021

Spiral-wound woven wire meshes packed bed rotating cylinder electrode was used for the simultaneous removal of cadmium (Cd) and copper (Cu) from a binary solution. The effects of weight percent of each metal on the removal and current efficiencies were studied at an operating current of 345A, while the effect of current on the removal efficiency of both metals was investigated at three levels of current (240, 345.and 400 mA). The experiments were carried out at constant rotation speed 800 rpm, pH = 3, and a total concentration of metals (500 ppm). The results showed that the removal efficiency of copper increased from 89% to 99.4% as its weight percent increased from 20% to100%. In a similar fashion, the removal efficiency of cadmium increased from 81% to 97% as its weight percent increased from 20% to100%. The results confirmed that the removal efficiency of any metals declined in the presence of the other. Increasing of current resulted in increasing the removal efficiency of both metals at different weight percents. The results confirmed that current efficiencies for removing of copper and cadmium simultaneously decline with increasing of electrolysis time and weight percent of cadmium or with decreasing the weight percent of copper. Current efficiency was higher at the initial stage of electrolysis for all weight percents of metals. The results showed that the decay of copper concentration was exponential at all weight percents of copper, confirming that the electrodeposition of copper is under mass transfer control in the presence of cadmium. While the decay of cadmium concentration was linear at lower weight percent of cadmium then changed to an exponential behavior at high weight percent of cadmium in the presence of copper.

• Korean Journal of Plant Tissue Culture
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• v.28 no.4
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• pp.221-225
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• 2001

Some factors of wounding methods, solidifying agents, origin of leaf explants, cone. of acetosyring-one, and MES affecting regeneration and transformation by Agrobacterium tumefaciens were investigated to establish an efficient transformation system of apple. Wounding by cutting the leaves merely showed the tendency of regeneration and transformation with higher efficiency compared with that of wounding by non-traumatic forcep when carrying out co-cultivation for three days after bacterial inoculation. While examining the solidifying agents of medium with the combination of agar (A)＋Gelrit $e^{ }$ (G) in g. $L^{-1}$ , the higher concentration of Gelrit $e^{ }$ increased the efficiency of regeneration. However, there was no difference in the efficiency of transformation from the treatments of 2.5 G, 3.5 A+1.2 G, and 7.0 G. The origin of leaf explants showed no difference statistically in the efficiency of regeneration and transformation, but that from the shoots of proliferation medium showed the tendency with higher efficiency. The concentration of above 0.1 mM acetosyringon had an increase in the efficiency of regeneration and transformation and the concentration of 0.15 mM had the highest efficiency of transformation in the treatment of acetosyringone with different concentration. There was no effect of MES on regeneration and transformation.ion.

• Journal of Environmental Health Sciences
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• v.37 no.1
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• pp.64-72
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• 2011

This study was performed to assess the removal efficiency on nitrogen, phosphorus and organic carbon in wastewater by spatial separation and internal recycling in a modified oxidation ditch process (modified OD). The performances of the modified OD were evaluated via laboratory-scale experiments. The process was operated at hydraulic retention times of 6-48 hours and solid retention times of 17-38 days. We found that organic carbon removal efficiency increased after the modified OD operation period. T-N removal efficiency remained stable; average T-N concentration of effluent was 8.02 mg/l after modified OD operation. In contrast, T-P concentration of effluent was over 1 mg/l. Nitrogen and phosphorus removal efficiency of modified OD at HRT 12 hr were 83.1% and 74.1%, respectively. Also, maximum efficiency was found at SRTs from 20 to 30 days. T-N removal efficiency was 83.1% at a C/N ratio from 3.0 to 3.5. However, T-N removal efficiency decreased at C/N ratios over 3.5. Also, T-P removal efficiency increased with HRT at C/P ratios in the same condition. Maximum efficiency was 74.1% at a C/P ratio from 25 to 28. T-N removal efficiency was 79.2% and T-P removal efficiency was 65.3% after M4 mode operation (added to the internal recycle line connected to the anoxic reactor). The modified OD with spatial separation and internal recycling developed in this study is, therefore, believed to be an improvement for solving problems in the nutrient removal technologies.

• Clean Technology
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• v.23 no.2
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• pp.181-187
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• 2017

The perfluorocompounds (PFCs) emitted from the semiconductor and display manufacture is treated by abatement systems which use various technologies, such as combustion, thermal, plasma, catalyst. However, it is required that the system should overcome their drawbacks with excess energy consumption and low removal efficiency. The new technology using combination of pressure swing adsorption and excess enthalpy combustion for the reduction of PFCs emissions were developed and analyzed its characteristics. PFCs concentration ratio and PFCs loss factor were calculated from measuring concentration of PFCs at the calculated by comparing concentration of PFCs at the combustor's inlet and outlet. There were performance evaluations with various gas flow for comparing energy consumption and removal efficiency with existing equipments. The concentration ratio and the loss factor of PFCs were 1.65, 8.2%, respectively, when the total gas flow of the pressure swing absorption (PSA) inlet was 204 liter per minute (LPM) and $CF_4$ concentration was 1412 ppm. In comparison with existing system at constant condition, $CF_4$ removal efficiency for a porous media combustion (PMC) showed the improvement more than 16% and the consumed energy was also reduced up to approximately 41%. Then, the total gas flow introduced into PMC and $CF_4$ concentration were 91-LPM and 2335 ppm, respectively, and the destruction and removal efficiency of $CF_4$ was about 96% at 19-LPM $CH_4$, and 40-LPM $O_2$.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.136-143
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• 2013

In this study, both transient behaviors of a biofilter system with improved design and a conventional biofilter were observed to perform the treatment of waste air containing malodor and volatile organic compound (VOC). Their behaviors of removal efficiency and treated concentration of malodor and VOC were compared each other. During 1st~7th stages of improved biofilter system operation it was observed that the order of treated ethanol concentration at each sampling port was switched due to the difference of microbe-population-distribution in spite of the difference of biofilter effective height. However, at 8th stage of its operation, the order of treated ethanol concentration at each sampling port was consistent to the order of biofilter effective height at each sampling port. The same was applied to the case of hydrogen sulfide, even though the difference of switched treated-hydrogen sulfide-concentrations was less than that of switched treated-ethanol-concentrations. The ethanol-removal efficiency of the biofilter system with improved design was ca. 96%, which was greater by 2% than that of the conventional biofilter. The transient behavior of treated hydrogen sulfide concentration of both biofilters were similar to each other. However, the concentration of hydrogen sulfide treated by the biofilter system with improved design was observed lower than that by the conventional biofilter. The hydrogen sulfide-removal efficiency of the biofilter system with improved design was higher by ca. 2% than that of the conventional biofilter. Therefore, the hydrogen sulfide-removal efficiency of the biofilter system with improved design was observed to be enhanced by the same as its ethanol-removal efficiency.