• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.36-40
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• 1993

The objective of this research was to retrofit an on-site sewage treatment system suitable to current situation of Korea to reduce the pollution loading and preserve the invaluable water resources. Operation at the F/M ratio of 0.1 kg. BOD/kg MLSS day showed 87.1% BOD removal efficiency and 84.5% COD removal efficiency, and its effluent concentration was 6.4 mg/l as BOD and 21.7 mg/l as COD. Average removal of total nitrogen showed high removal efficiency of 80%.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.30-36
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• 2002

A 0.19 hectare natural-type wetland for stream water treatment demonstration was constructed and planted with cattails from April 2001 to May 2001. Part of its bottom surfaces adjacent to levees have a variety of slope of 1 : 4~1 : 15. Two small open water areas were installed, in which emergent plants could not grow. Removal of nutrients from stream waters was a major objective of the wetland. Waters of Sinyang Stream flowing into Kohung Estuarine Lake were pumped and funneled into the wetland. The lake had been formed by a salt marsh reclamation project and was located southern coastal region of Korean Peninsula. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged $120.4m^3/day$ and $112.1m^3/day$, respectively. Hydraulic retention time was about 3.1 days. Average total phosphorous concentration of influent and effluent was $0.19mg/{\ell}$ and $0.075mg/{\ell}$, respectively. Total phosphorous loading rate of inflow and outflow averaged $12.05mg\;m^{-2}\;day^{-1}$ and $4.44mg\;m^{-2}\;day^{-1}$, respectively. Average total phosphorous removal rate in the wetland was $7.61mg\;m^{-2}\;day^{-1}$. Seasonal changes of phosphorous retention rates were observed. The wetland acted as effective phosphorous sinks in the initial stage of the constructed wetland.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.703-709
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• 2013

Among many microalgae cultivation types, heterotrophic culture with low cost carbon sources and energy saving culture method is crucial. A result of estimating the effects of pH on wastewater treatment using heterotrophic growing microalgae Chlorella sorokiniana shows that there was no difference in microalgae growth amount and nitrogen, phosphorus removal rate by wide range of pH(5 ~ 9). From pH 5 to 9, total nitrogen, phosphorous and glucose removal rates were 10.5 mg-N/L/d, 2 mg-P/L/d, 800 ~ 1000 mg/L respectively. This study reveals that C. sorokiniana cannot metabolite glycerol heterotrophically, however, glucose and acetate were proper carbon sources for growth and T-N, T-P and TOC removal. This research highlights the potential of heterotrophic microalgal growth with wastewater treatment plant with wide range of pH and carbon sources.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.9-17
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• 2014

PURPOSES : The purpose of this study is to assess removal efficiency of non-point pollutants and applicability for non-point pollutant reduction facilities by conducting the demonstration project operation. METHODS : In order to analyze removal efficiency of non-point pollutants for facilities such as a grassed swale, a small constructed wetland, a free water surface wetland, a horizontal sub-surface flow wetland, and a sand filtration, the field data including specifications of facilities, rainfall, inflow and runoff rainfall effluent etc. was acquired after occurring rainfall events, and the acquired data was analyzed for removal efficiency rate to assess road non-point pollutants facilities using event mean concentration (EMC) and summation of load (SOL) methods. RESULTS : The results of analyzing rainfall effluent, non-point pollutant sources showed that total suspended solid (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), chrome (Cr), zinc (Zn), and lead (Pb) can be removed through non-point pollutant reduction facilities by 60.3% ~ 100%. Especially removal efficiency of TSS, COD and BOD is relatively higher than removal efficiency of other non-point pollutant sources in all kind of non-point pollutant facilities. CONCLUSIONS : Based on the result of this study, even though natural type of non-point pollutant reduction facilities for roads occupy small areas comparing with drainage basin areas, most of non-point pollutant sources would be removed through the facilities.

• The korean journal of orthodontics
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• v.52 no.3
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• pp.201-209
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• 2022

Objective: To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors. Methods: The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque. Results: The mean period of total in-bone stay of microimplants in the post-retention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4-5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively. Conclusions: The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

• Journal of Environmental Science International
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• v.22 no.11
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• pp.1383-1388
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• 2013

The pilot plant experiment was performed to investigate phosphorus and nitrogen removal from domestic wastewater by MLE process combined with aluminum corrosion reactor. When operating 0.5Q and 1Q to internal recycle and sludge recycle in the MLE process, the effluent $COD_{Mn}$ concentration of internal recycle 0.5Q were higher than internal recycle 1Q, the removal efficiency rates of $NH_3$-N in the internal recycle 0.5Q were was higher than internal recycle 1Q. Denitrification rates were about 86.8% in internal recycle and sludge recycle 0.5Q. When operating 0.5Q to internal recycle and sludge recycle in the MLE process, the removal efficiency rates of total nitrogen was the highest. The removal efficiency rates of total phosphorus was about 91.5% in the aluminum corrosion reactor.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.580-587
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• 2004

The objective of this research is to investigate the electrochemical oxidation process for nitrogen removal in wastewater involving chloride ion and nitrogen compounds. The process experiment of electrochemical oxidation was conducted by using the stainless steel tube type reactor and the $Ti/IrO_2$ as anode. Free chlorine production and current efficiency variation for total nitrogen removal was compared depending on whether electrolyte is added, and the nitrogen type distribution under an operating condition. When chloride was added as electrolyte, it was found that production of free chlorine increased and the concentration of the chloride decreased as retention time passed. The concentration of chloride in influent decreased from 1,660 to 1,198 mg/L at the current density of $6.7A/dm^2$, while concentration of free chlorine increased to 132 mg/L. Current efficiency in removal of ammonium nitrogen was increased when chloride was dosed as electrolyte. It was observed that ammonium nitrogen was oxidized to nitrite and nitrate through electrochemical oxidation and that the concentration of total nitrogen in influent was reduced from 22.58 to 4.00 mg/L at the short retention time of 168 seconds through the electrochemical oxidation of nitrogen.

• Journal of Soil and Groundwater Environment
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• v.18 no.7
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• pp.18-24
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• 2013

The influences of various operating parameters on physico-chemical techniques were evaluated to remediate petroleum-contaminated sandy soil including S/L ratio, kinetic, and effect of soil particle size. The simple extraction using tap water removed only 20.6% of total petroleum hydrocarbon (TPH), and addition of NaOH enhanced the removal of TPH to approximately 30%. To meet the regulation levels, a surfactant, sodium dodecyl sulfate, was added, and the removal of TPH increased to 4 times. Probably, the carbonate minerals affected chemical aging and soprtion of petroleum, which inhibited the extraction of TPH. The soil with smaller particle size contained more TPH, and the removal of TPH was obstructed with smaller particle size. However, NaOH addition increased the removal of TPH in the smaller particles. The physico-chemical properties of soil influenced greatly the removal of petroleum even in sandy soil.

• Journal of Acupuncture Research
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• v.23 no.1
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• pp.135-143
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• 2006

Objectives : This study was performed to observe effect of acupuncture stimulation on heart rate variability in stroke patients. Methods : Data were obtained from heart rate variability of 29 stroke patients. Heart rate variability was measured total five times(before and after needle insertion, before and after needle removal, and 10 minutes after needle removal) for five minutes each time. Results : Heart rates were continuously decreased until 10 minutes after needle removal. SDNN, Total power, LF, and HF were increased until 5 minutes after needle removal, but deceased between 5 and 10 minutes after needle removal. There was no significant changes between male and female and among age groups. Conclusion : This study showed that acupuncture stimulation could effect on heart rate variability in stroke patients. Heart rate variability could be a objective tool to verify the mechanism of acupuncture effect in various condition.

• Environmental Engineering Research
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• v.15 no.4
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• pp.225-230
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• 2010

In order to treat soil contaminated with high percentages of water and petroleum, the combined microwave and thermal desorption process was studied, which was composed of the consecutive connection of two pre-treatment processes. For the thickness of the contaminated soil layer on the transfer conveyor belt, the optimal total petroleum hydrocarbon (TPH) removal rate was studied with respect to the duration of microwave exposure in the consecutive process combined with thermal desorption. The TPH removal rate when the contaminated soil layer thickness was 1 cm at 6 kW of microwave power was 80%. The removals rates for 2 and 3 cm soil layer thicknesses were both 70%. Under identical experimental conditions, the TPH removal rate for the microwave pre-treatment, when considering the soil particle size, was over 70%. The lowest TPH removal rate was achieved with a particle diameter of 2.35 mm. For contaminated soil with 30% water content, 6 kW and a thermal desorption temperature of $600^{\circ}C$ were the optimal operational conditions for the removal of THP. However, considering the fuel consumption cost, 4 kW and a thermal desorption temperature of $300^{\circ}C$ would be the most economic conditions.