• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.779-785
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• 2013

This study investigated the applicability of a two step microfiltration(MF) and reverse osmosis(RO) membrane system for reuse of tunnel wastewater. In this two step process, the MF system first treated only micropollutants in tunnel wastewater such as suspended solids(SS) and heavy metals, achieving less than 0.2 NTU turbidity, less than 1.1 mg/L chemical oxygen demand($COD_{Mn}$) and less than 0.8 mg/L total manganese(Mn). The RO system then removed over 95 % of the remaining pollutnats and particles, resulting in less than 0.02 NTU turbidity, less than 0.5 mg/L chemical oxygen demand($COD_{Mn}$), less than 0.04 mg/L total nitrogen(T-N) and less than 0.01 mg/L total phosphorus(T-P). In particular, addition of an RO system could lead to markedly reduced high salt concentrations in tunnel wastewater, approaching almost zero. Thus, reclaimed water using the combined membrane system could satisfy current South Korean regulations concerning wastewater reuse(turbidity ${\leq}2.0$ NTU; T-N ${\leq}10mg/L$; T-P ${\leq}0.5mg/L$; Salinity ${\leq}250mg{\cdot}Cl/L$).

• Smart Structures and Systems
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• v.6 no.7
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• pp.767-792
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• 2010

In this paper, the optimal design of vibration control system for smart structures has been investigated semi-analytically via the optimization of geometric parameters like the placements and sizes of piezoelectric sensors and actuators (S/As) bonded on the structures. The criterion based on the maximization of energy dissipation was adopted for the optimization of the control system. Based on the sensing and actuating equations, the total energy stored in the system which is used as the objective function was analytically derived with design variables explicitly presented. Two cases of single and combined vibration modes were addressed for a simply supported beam and a simply supported cylindrical shell. For single vibration mode, the optimal distributions of the piezoelectric S/As could be obtained analytically. However, the Sequential Quadratic Programming (SQP) method has to be employed to solve those which violated the prescribed constraints and to solve the case of combined vibration modes. The results of three examples, which include a simply supported beam, a simply supported cylindrical shell and a simply supported plate, showed good agreement with those obtained by the Genetic Algorithm (GA) method. Moreover, in comparison with the GA method, the proposed method is more effective in obtaining better optimization results and is much more efficient in terms of computation time.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1378-1382
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• 2005

여름철 집중강우시 유입되는 고탁수층은 저수지의 밀도성층으로 인하여 표수층 하부에 위치하며, 이를 적기에 배제하지 않을 경우에는 수평방향의 확산현상과 연직방향의 전도현상으로 인해 저수지 전역에 분포하게 되어, 탁수현상의 장기화를 유발한다. 이와 같은 탁수장기화에 대한 저수지내 대책의 하나로서 홍수유입후 탁도가 높은 물을 단기간동안 방류하고, 갈수기에는 탁도가 낮은 물을 방류하는 선택취수 기법을 적용할 수 있다. 임하댐의 경우, 2004년 태풍 '디앤무'와 태풍 '메기'로 인해 발생한 탁수를 선택취수를 통하여 조기에 배제함으로써 호내탁도를 저감시킨 바 있다. 그러나 이와 같은 고탁수 우선배제 기법은 반드시 하류하천의 영향범위를 사전에 분석검토하고, 하류하천의 수질현황을 고려한 합리적인 운영방안이 제시되어야 한다. 2004년 태풍 '디앤무' 발생직후의 댐방수로에서 170 NTU의 고탁수를 방류한 경우, 유하거리 250 km인 지점까지 30 NTU이상 유지된 바 있으며, 태풍 '메기'에 의한 고탁수 유입시, 임하댐 방류수 157 NTU, 안동댐 방류수 37 NTU인 경우에 임하댐 하류 113 km인 구미 선산 취수장까지 63 NTU의 탁도가 유지된 바 있다. 현재 임하댐의 경우, 하류하천으로의 방류수 수질을 모니터링할 수 있는 자동수질측정시스템이 발전취수탑 전면 1개소, 조정지댐 1개소에 설치되어 있다. 본 연구에서는 자동수질측정시스템과 연계하여 수질모형을 통하여 임하댐 하류하천인 낙동강 본류의 탁도관리시스템을 구축하고자 하였다. 환경부의 수질측정망 자료를 통하여 최근 3년간의 부유사농도의 변화양상을 분석하였으며, 태풍 직후의 낙동강 주요지점별 탁도측정자료를 이용하여 임하댐 고탁도방류에 의한 영향범위를 분석하였다. 또한 하천수질모형을 이용하여 탁수예측방법에 대하여 검토하였고, 이를 이용한 탁도관리시스템 구축을 위한 기본 방향을 제시하고자 한다.함께, 2단계에 (주)웹솔루스에서 자체적으로 설치 운영하고 있는 2개소의 하수관거 모니터링 관측시설, 그리고 안양시에서 운영하고 있는 5개소의 강우관측소와 7개소의 수위관측소를 모두 통합하여 실시간 자료를 제공하고 있다. 수위자료는 10분단위의 텍스트정보와 그래프형태로 지원되며, 검색기간 설정을 통해 원하는 기간내의 자료를 선별, 검색할 수 있다.. 또한 이와 같은 기초적인 정보를 바탕으로 하류하천의 탁수 피해를 최소화할 수 있는 선택취수탑의 운영방안을 수립할 수 있다 본 연구에서는 이를 위해 선택취수탑 주위의 성층흐름을 기존의 실험자료와 수치해석을 통하여 분석하였고, 온도성층구조나 취수구의 위치변화에 따른 방류수 수질특성을 조사하였다.쇄파대(artifical reef)와 같은 완충지대를 갖는 호안을 축조함으로써 월파량을 감소시키는 대안으로 제시하고자 한다. 본 연구 수행을 통해 태풍 내습시 발생 가능한 자연재해에 대한 사전 방지를 목적으로 태풍피해의 원인을 제시하고 이를 해결하여 현재의 방재대책이 항구적인 방재대책으로 전환될 수 있는 방안 마련의 기초 자료로 활용되기를 기대한다., L-arabinose, 및 D-galactose; 제3차(第三次) 가수분해물(加水分解物)(C)에서 L-rhamnose, D-xylose, L-arabinose 및 D-galactose, 비가수분해물(非加水分解物)(C')에서 D-xylose와 D-galactose를 검출(檢出)하였다. (4) 구성당(構成糖)의 형태(形態)와 구조(構造)를 밝히기 위(爲)해 polysaccharide C에 대한 periodate산화(酸化) 실험(實驗)을 하여 $C_5H_8O_4$당(當) periodate의 소비(消費)와 formic acid의 생성량(生成量)을 측정(測定)하였는데 periodate의 소비량(消費量)은 1.23 mole, formic acid의 생성량(生成量)

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.301-306
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• 2013

This research was conducted to investigate whether sequential anoxic/aerobic biofilm reactors and microfilteration (MF) membrane system can be used as a direct treatment for the removal of perchlorate and nitrate in groundwater. The biofilm process consisted of an anoxic first stage to remove perchlorate and nitrate and aerobic second stage to remove remaining acetate used as a carbon source for dissimilatory reduction of perchlorate and nitrate. In final stage, hollow fiber MF membrane was used to remove turbidity. In this research, perchlorate was reduced from the influent concentration of 102 ${\mu}/L$ to below the IC detection level (5 ${\mu}/L$) and nitrate was reduced from 61.8 mg/L (14 mg/L $NO_3$-N) to 4.4 mg/L (1 mg/L $NO_3$-N). Acetate used as a carbon source was consumed from 179 mg/L $CH_3COO-$ to 117 and 11 mg/L $CH_3COO^-$ in effluents from anoxic and aerobic biofilm reactors, respectively. Turbidity was reduced from 3.0 NTU to 1.5, 0.3, and 0.2 NTU in effluents from anoxic/aerobic biofilm reactors and MF membrane, respectively. It is expected that the sequential anoxic/aerobic biofilm reactors and MF membrane system can efficiently remove perchlorate and nitrate in surface water or groundwater.

• Membrane Journal
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• v.20 no.2
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• pp.97-105
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• 2010

This study was to evaluate the performance of the Double stage Pore controllable fiber (DP) filter system as the pre-treatment of the RO membrane. The evaluation for the pre-treatment filter was performed through the indirect method, SDI (Silt Density Index) measurement of the filtrate. This study was done during Jan. 3 of 2009 to Dec. 3 of 2009 at OO Water Treatment Plant that was suppling industrial water to plants, and the raw water was contaminated lake water and it was fed to the system after clarification with coagulation. The average turbidity of the feed water and that of the filtrate was 0.79 NTU (0.28~4.01 NTU), and 0.16 NTU (0.04~0.50) respectively. And so the average turbidity removal efficiency was 77%. The filtrate flow rate and the backwash water flow rate was about 230 $m^3$/day and about 8.7 $m^3$/day respectively, and so the backwash rate was 3.8%. The data for some samples were obtained after a few days storage, and it caused the higher turbidity and SDI15 as the storage time was increased. But average SDI value of the filtrate was 3.6 (2.26~5.00) which was lower than minimum value required by the RO membrane manufacturer as the RO feed water to guarantee the life time of the RO membrane. So, the DP filter system was enough for the application as the pre-treatment of the RO membrane.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.37-43
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• 2006

The coagulation efficacy of Al-based coagulants (such as Alum, PACS, and PACC) was investigated to ascertain removal efficiencies of turbidity and phosphate with variation of solution pH, coagulant dosages, and pre-dilution ratios. The efficacy of Al-based coagulants was maximized in the pH range of 6~9. Under the initial condition of pH 8, $10mg/L\;{PO_4}^{3-}$, and 20 NTU, Al-based coagulants exhibited a similar efficacy in the removal of turbidity, whereas the removal efficiency of phosphate was clearly dependent on the basicity of coagulants: Alum (0%) > PACS (45~50%) > PACC (70%). At high initial turbidity of 100 NTU, polymeric coagulants, such as PACS and PACC, exhibited a higher removal efficiency of turbidity compared to Alum. In comparison to direct injection of coagulants at low initial turbidity (20 NTU), 500~2000 times pre-diluted Alum, exhibited reduced coagulation efficacy; however, removal efficiencies of turbidity and phosphate increased with the increase of retention time. Pres-diluted PACC exhibited the enhanced coagulation efficacy followed by silght decrease of the removal efficiencies with increase of the retention time. At high initial turbidity of 100 NTU, pre-diluted Alum and PACC exhibited higher removal efficiencies of turbidity and phosphate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1018-1027
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• 2003

This study treats the analysis of the performance and the design of plume abatement wet/dry cooling tower with dry type heat exchanger using a numerical method. A two-dimensional analysis is performed using the finite volume method for mechanical draft counterflow and crossflow tower. For a coupling problem between water and air system, a turbulent two phase flow is considered. Effectiveness-NTU method is used for modeling of the dry type heat exchanger. The parameter change simulations of the outer wall shape, the relative flowrate of air, and attachment of an air mixer are performed to examine the effect on plume abatement. It is found that if the relative air flowrate ratio and the adequate air mixer type are chosen well in addition to the ratio of water to air flowrate, the loss of the cooling capacity and the additional cost are reduced and the plume is abated.

• Journal of Environmental Science International
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• v.20 no.5
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• pp.639-645
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• 2011

This study found that flotation efficiencies for removing algae and micro particles in raw water were optimized on mixing intensity and time of the mixing and flocculation conditions with a continuous DAF system. It is more efficient for mixing intensity at 23.1 $s^{-1}$ and time at 660 s(Gt value : 15246) to float flocculated floc with the raw water in M water treatment plant. Flotation efficiency was more than about 0.9 when operated pressure and A/S ratio were sustained at 5 $kg_f{\cdot}cm^{-2}$ and up to 0.056 $mL{\cdot}mg^{-1}$. The continuous DAF system made by the study could be continuously operated for 20 days and sustained not exceeding 4 NTU with raw water with low turbidity(13.4~9.8 NTU).

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.51-60
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• 2002

An analysis method to predict performance of a vehicle cooling system which is composed of radiator, A/C condenser, cooling fan, and etc. is suggested. Air flow through the heat exchanger system and heat rejection rate which dominate the cooling performance are analyzed. Heat transfer with A/C refrigerant phase change is also considered in the analysis. Some predicted results are compared with experimental data for various operating conditions. This evaluation procedure will be useful for the design of optimal vehicle cooling system.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.3
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• pp.260-270
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• 2000

The objective of this study is to evaluate the effect of filter aids in the dual-media rapid filtration. Paper-filter tests were conducted to determine the proper dosages of coagulant and filter aid, and pilot plant tests using two dual-media filter columns were performed for a variety of filtration rates. Using a filter aid (non-ionic polymer), the maximum feasible filtration rate is 480m/day, while turbidity is less than 0.3 NTU and filter run-time is about 70 hours. It is possible to increase the filtration rate up to 360 m/day for keeping the turbidity less than 0.1 NTU. Turbidity increases for the filtration rate greater than 360m/day. In general, the quality of filtered water with a filter aid is stable, while the filter maintains a sufficient filter run-time for a maximum allowable head loss. Particularly, the initial breakthrough can be effectively controlled. The use of a filter aid may be one of the methods applicable if the turbidity of filtered water is required to be improved or if the filter breakthrough limits filter run-time.