• Journal of Industrial Technology
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• v.2
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• pp.33-44
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• 1982

This study mainly concentrated on the treatment of nightsoil by an anaerobic filter media process. Nightsoil has been one of the major water pollutants in this couotry. It represents high ROD and SS concentrations. A comprehensive laboratory study conducted at Kangwoon National University indicate: (1) In the case of anaerobic filter system, COD and BOD removal efficiencies were greatly influenced by hydraulic retention time(HRT), but SS removal efficiencies dropped slowly when HRT were 2~13 days. (2) COD removal efficiencies were 19% when HRT were 15 days, 14% when HRT were 8 days, 10% when HRT were 6 days, 9% when HRT were 4 days, 2% when HRT were 2 days. (3) BOD removal efficiencies were 23% when HRT were 15 days, 14% when HRT were 8 days, 18% when HRT were 6 days, 7% when HRT were 4 days, 5.8% when HRT were 2days. (4) SS removal efficiencies were 21%~25%(2~15 days HRT).

• KSBB Journal
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• v.23 no.4
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• pp.323-328
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• 2008

This study was accomplished using Anaerobic/Anoxic/Oxic biofilm reactors with fixed media and post-treatment reactor for natural purification with aquatic floating plants. The objectives of this study was to investigate the characteristics of organics, nitrogen and phosphorus removal from sewage with the HRT. The average removal efficiency of SS and $COD_{Cr}$ increases as increasing the hydraulic retention time (HRT) until 12 hr of the HRT, and it was constant over 12 hr of the HRT. The removal efficiency of them was about 93% and 89% respectively over the 12 hr of HRT. The average $BOD_5$ and $COD_{Mn}$ increases as increasing the HRT and the removal efficiency of them was 84.91 % and 76.03% respectively at the 26 hr of HRT. The removal efficiency of T-N and T-P increases as increasing the HRT until 61 hr of the HRT, and it was constant over 61 hr of the HRT. At the HRT of 61 hr, it was 70.20%, 77.86% respectively. It was found that the optimum HRT was 61 hr in case of the nutrients. Before and after experiment, the nitrogen content was similar in leaves of the water hyacinths but the nitrogen content in roots after experiment was 5.5% more than its content before experiment. It was known that the nitrogen was absorbed by the water hyacinths.

• KSBB Journal
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• v.24 no.4
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• pp.353-360
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• 2009

This study was accomplished using Anaerobic/Anoxic/Oxic upflow packed-bed column reactors with fixed media and Loop Reactor with fluidized media instead of Oxic reactor. The objectives of this study was to investigate the characteristics of organics, nitrogen and phosphorus removal from sewage with the HRT. The average removal efficiencies of $BOD_5$ and SS increase as increasing the hydraulic retention time (HRT) until 16 h of the HRT, and they were constant over 16 h of the HRT. The removal efficiency of $BOD_5$ in case of packed-bed reactor and Loop Reactor was about 86.6% and 90.9% respectively at 16 h of the HRT. The removal efficiency of SS in packed-bed reactor and Loop Reactor was about 78.0% and 88.2% respectively at 16 h of the HRT. The average removal efficiencies of $COD_{Cr}$ and $COD_{Mn}$ showed similar trends as those of $BOD_5$ and SS. At the HRT of 16 h, the removal efficiency of $COD_{Cr}$ in case of packed-bed reactor and Loop Reactor was 63.5%, 75.2% and that of $COD_{Mn}$ was 60.7%, 73.6% respectively. The average removal efficiencies of T-N and T-P increase as increasing the HRT. The removal efficiencies of T-N and T-P in Loop Reactor were 33.6% and 54.5% respectively at 16 h of the HRT and T-N and T-P were better removed in Loop Reactor. From this result, it was found that the performance of Loop Reactor was much higher than the performance of packed-bed reactor and the optimum HRT was 16 h.

• The Journal of Korean Obstetrics and Gynecology
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• v.19 no.1
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• pp.219-235
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• 2006

Purpose : To investigate the medical information related to HRT online and the medical treatment of perimenopausal and postmenopausal women in the Dept. of Ob&Gy Korean Medicine Hospital, after the discontinuance of the WHI trial in U.S, July 2002. Methods : With the key-words "HRT", "Hormone Replacement therapy", "호르몬 대체요법(HRT)", 갱년기 증후군(perimenopausal syndrome)", “폐경기후증후군(postmenopausal syndrome)", I searched for the information from July 2002 to 2005 on DAUM, the representative portal site in Korea, and I've got a grasp of the tendency of the informational propagation on HRT. Moreover, I investigated chief complaints and tendency of give up HRT of the perimenopausal and postmenopausal women(aged between 47 and 60) who visited Dept. of Ob&Gy Korean Medicine Hospital for 2 years and 6 months since July 2002. Results : 1) Searching for the news on DAUM, I found; 2 articles on the methods of HRT: 4 on the positive effects of HRT: 4 on the general items including the positive effects of HRT: 19 on the side effects of HRT: 1 on the insignificant effect of HRT :4 on the apprehensions about HRT: 3 on the strengthening of the criteria on medical fees review: 3 on the discontinuance of HRT: 8 on the alternative materials and medicines to HRT: 4 on the guidance for the phyto-estrogen. 2) I analyzed chief complaints of 120 women. The majority of chief complaints were vasomotor symptoms like hot flush and sweating. There were only 4 patients who wanted to give up HRT. Conclusion : The side effects of HRT were objectively dealt with online but there was not enough effective and continuous guidance. In the case that a woman not on HRT wishes to overcome perimenopausal period through KM therapy, this information may have affected her decision. However, not many women who were already on HRT terminated the therapy for fear of side effects and switched to KM therapy. Promotion of KM therapy in improving health during perimenopausal and postmenopausal period is desperately needed.

• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.365-370
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• 2002

This study aims to study the effect of HRT and influent concentration on swine wastewater treatment using UASB(Upflow Anaerobic Sludge Blanket). Sample was separately collected from the piggery farm; urine(liquid part) and solid part to compare their treatment characteristics. Reactors were used two UASB(3.2 L) in this research under constant temperature ($35^{\circ}C$). Their operating conditions were as follows; Run 1(UASB ; HRT 6-days, 1 cycle/d), Run 2(UASB ; HRT 3-days, 1 cycle/d). Biogas was collected and analyzed using GC(HP-6890). By comparing the results of Run 1 and Run 2, the effect of HRT was investigated. The treatment efficiency of Run 1 which had longer HRT was higher than that of Run 2 in both solid and liquid parts of piggery sample. Methane content in collected biogas is more than 80%.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.911-916
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• 2006

The influence of substrate concentration and hydraulic retention time(HRT) on the hydrogen production by anaerobic microflora was investigated by conducting three series of continuous experiments the individual influences of substrate concentration and HRT. In series I, substrate concentration was increased from 3 to 27 g-glucose/L keeping HRT at 8 hr. Series II and III carried out same condition with series I at HRT of 16 hr and 24 hr, respectively. The effects of HRT and substrate concentration on the hydrogen production yield were analyzed by quadratic model. The maximum hydrogen production yield of 2.05 mol $H_2/mol$ glucose was found at the HRT of 9.6 hr and the substrate concentration of 15.4 g/L. The relationship between HRT and substrate concentration on hydrogen production yield as displayed a saddle shape in the response surface plot. Optimum HRT and substrate concentration are observed at in the range of 5 and 14 hr, at between 13 and 17 g/L, respectively, for the hydrogen production yield being 2 mol $H_2/mol$ glucose. The concentrations of organic acids increased with the increase of the amount of glucose consumption. Acetic acid and butyric acid were the main by-products from the glucose degradation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.117-127
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• 1983

An experimental research was performed employing the two stage anaerobic digestion of the mixture of the nightsoil and septic tank sludge to determine the effects of various hydraulic retention time of the digestion on chemical characteristics and treatment effeciency, thus determining the proper retention time. Results of the research are as follows, 1. Volatile-acid decreased as HRT increased. 2. Alklinity and ammonia-N tended to increase as HRT increased as did pH values, however, were observed to be constant at higher HRT values than 15 days. 3. The removal efficiencies of TBOD, TCOD and VS increased as HRT increased. 4. The removal efficiency of volatile solid decreased as VS loading increased. 5. It was observed that the rates of gas production were: 0.33 with HRT of 5 days, 0.58 with HRT of 15 days and $0.57m^3/kg$ VS fed/day with HRT of 25 days respectively. It is believed that the highest rate of gas production was at HRT of 15 days. 6. The sludge settling experiment showed that the minimum settling time required to ensure the desired underflow concentraton was estimated to be 8.6 days.

• Journal of Aquaculture
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• v.16 no.3
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• pp.142-150
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• 2003

Performance of a biological filter, the rotating biological contactor (RBC), is affected by rotational speed and hydraulic residence time (HRT). A RBC with a disc diameter of 62 cm, total surface area of 48.28 $m^2$, volume of 0.34 ㎥, and submergence ratio of 35.4% was tested for the combinations of five rotational speeds (1, 2, 3, 4 & 5 rpm) and three HRT (0.5, 1.0 & 2.0 hr) to find out the maximum removal efficiencies of total ammonia nitrogen (TAN) and nitrite nitrogen of a simulated recirculating aquaculture system. Ammonia loading rate in the system was 25 g of TAN/ ㎥. day. Removal efficiencies were checked when TAN concentrations in the system stabilized for 3 days in each treatment. The concentration of TAN in the system decreased with increasing rotational speed of the RBC up to 4 rpm in all HRT (P<0.05). At the rotational speed of 5 rpm, the efficiencies decreased in all HRT (P<0.05). When the rotational speeds were 1, 2, 3, 4, and 5 rpm, TAN concentrations in the system were 1.35, 0.94, 0.69, 0.66, and 0.76 mg/L at the 0.5 hr HRT, 2.86, 1.18, 0.96, 0.87, and 1.11 mg/L at the 1.0 hr HRT, and 5.30, 2.44, 1.99, 1.77, and 2.01 mg/L at the 2.0 hr HRT, respectively. The TAN removal efficiencies of the RBC at the rotational speeds of 1, 2, 3, 4, and 5 rpm were 32.9, 49.5, 65.1, 72.9, and 62.9% in 0.5 hr HRT,33.1, 74.1, 87.1, 95.8, and 78.5% in 1.0 hr HRT, and 35.5, 76.7, 89.6, 97.0, and 85.5% in 2.0 hr HRT, respectively. TAN removal efficiency of RBC per pass increased with increasing HRT. However, TAN concentration in the system also increased. The best operating condition among the treatments was obtained at the treatment of 0.5 hr HRT and 4 rpm (P<0.05). The TAN concentration was 0.66 mg/L. Concentrations of nitrite nitrogen (NO$_2$$^{[-10]}$ -N) in the system decreased with increasing rotational speed in all HRT while that in the system increased with increasing HRT in all rotational speeds. The ranges of NO$_2$$^{[-10]}$ -N concentrations at HRT of 0.5, 1.0, and 2.0 hr in the system were 0.26~0.32, 0.31~0.56, and 0.43~l.45 mg/L, respectively. The ranges of daily removal rates of TAN in this system were 20.03~23.0 g TAN/㎥ㆍday and those of nitrite nitrogen were 19.65~30.25 g NO$_2$$^{[-10]}$ -N/㎥ㆍday.

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

• The Plant Pathology Journal
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• v.19 no.1
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• pp.19-23
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• 2003

Turnip crinkle vims (TCV) inoculation onto resistant Arabidopsis ecotype Dijon（Di-17) leads to a hypersensitive response (HR) on the inoculated leaves. A dominant gene, HRT, which confers an HR to TCV, has been cloned from Di-17 plants by map-based cloning. HRT is a LZ-NBS-LRR class resistance gene and it belongs to a small gene family that includes RPP8, which confers resistance to Peronospora parasitica Emco5. Outside of the LRR region, HRT and RPP8 proteins share 98% amino acid identity while their LRR regions are less conserved (87% identity). HRT-transformed Arabidopsis plants developed an HR but generally remained susceptible to TCV due to a dominant RRT allele, which is not compatible with resistance. However, several transgenic plants that over-expressed HRT much higher than Di-l7 showed micro-HR or no HR when inoculated with TCV and were resistant to infection. Both the HR and resistance are dependent on salicylic acid but independent of NPRI, ethylene, or jasmonic acid. Arabidopsis plants containing both TCV coat protein gene and HRT developed massive necrosis and death in seedlings, indicating that the TCV coat protein is an avirulence factor detected by the HRT.