• Environmental engineer
• /
• s.173
• /
• pp.71-76
• /
• 2001

본 연구과제는 기존의 응집제에 비하여 우수한 신규 응집제를 개발하는 것으로 목표로 추진했다. 그간의 연구에서 기존의 응집제에 비하여 탁월한 응집성능을 발휘하는 고염기도(70$\%$)응집제인 Ca-PAX를 개발하였다. Ca-PAX는 탁도 제거에서 기존의 PAC에 비하여 70$\%$ 이하의 투입량으로도 동일한 처리결과를 보이며, 유기물 제거에서도 탁월한 성능을 보였다. 또한 적은 투입량으로도 우수한 처리성능을 보이기

• Proceedings of the Korean Society for Information Management Conference
• /
• 2005.08a
• /
• pp.65-70
• /
• 2005

계층적 문서 클러스터링에 있어서 실험집단에 따라 응집식 기법과 분할식 기법의 성능이 다르며, 이를 좌우하는 요소는 분류의 깊이, 즉 분류수준이라고 가정하였다. 조금만 나누면 되는 대분류인 경우는 상대적으로 분할식 기법이 유리하고, 조금만 합치면 되는 소분류인 경우에는 응집식 기법이 유리할 것이라고 판단했기 때문이다. 그에 따라 분할식 클러스터링 기법인 양분(Bisecting) K-means기법과 응집식 기법인 완전연결, 평균연결, WARD기법의 성능을 실험집단이 대분류인 경우와 소분류인 경우의 유사계수를 적용하여 각 기법별 성능을 비교하여 실험집단의 특성에 따른 적합 클러스터링 기법을 찾고자 하였다. 실험결과 응집식 기법과 분할식 기법의 성능 우열에 영향을 미치는 것은 분류수준보다는 변이계수로 측정된 상대적인 군집의 크기 편차인 것으로 나타났다.

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

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.3
• /
• pp.269-275
• /
• 2014

The objective of this study was to investigate the performance characteristics of an inline mixing and coagulation system for water treatment based on the process intensification concept. Three-stage inline mixing and coagulation system was composed of the reservoirs of source wastewater, the fixed quantity injection pumps of coagulants, the mixing and coagulation tubes, a sedimentation tank and a control panel. In the equal dosage of coagulant and coagulant aids, the turbidity removal with increasing the dosage of coagulant aids was about 3 times higher than that with increasing the dosage of coagulant. In the condition of the equal mixing and coagulation time, the turbidity removal of inline mixing and coagulation system was about 4.6 times higher than that of mechanical type.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.7
• /
• pp.514-520
• /
• 2014

In this study, the production potential of alternative coagulant ($Al_2(SO_4)_3$ solution) having the identical coagulation activity with respect to the commercial coagulant was investigated. The raw material of alternative coagulant was a spent catalyst including aluminium (waste activated alumina) generated in the manufacturing process of the polymer. The alternative coagulant was produced through a series of processes: 1) intense heat and grinding, 2) chemical polymerization and substitution with $H_2SO_4$ solution, 3) dissolution and dilution and 4) settling and separation. To determine the optimal operating conditions in the lab-scale autoclave and dissolver, the content of $Al_2O_3$ in alternative coagulant was analyzed according to changes of the purity of sulfuric acid, reaction temperature, injection ratio of sulfuric acid and water in the dissolver. The results showed that the alternative coagulant having the $Al_2O_3$ content of 7~8% was produced under the optimal conditions such as $H_2SO_4$ purity of 50%, reaction temperature of $120^{\circ}C$, injection ratio of $H_2SO_4$ of 5 times and injection ratio of water of 2.3 times in dissolver. In order to evaluate the coagulation activity of the alternative coagulant, the Jar-test was conducted to the effluent in aerobic reactor. As a result, in both cases of Al/P mole of 1.5 and 2.0, the coagulation activity of the alternative coagulant was higher than that of the existing commercial coagulant. When the production costs were compared between the alternative and commercial coagulant through economic analysis, the production cost reduction of about 50% was available in the case of the alternative coagulant. In addition, it was identified that the alternative coagulant could be applied at field wastewater treatment plant without environmental problem through ecological toxicity testing.

• Clean Technology
• /
• v.8 no.2
• /
• pp.85-92
• /
• 2002

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M $H_2SO_4$ solution with 10g of red mud at $85^{\circ}C$ or by reacting 100ml of 9M HCl solution with 10g of red mud at $25^{\circ}C$. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant ($FeCl_3$). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by $FeCl_3$.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.7
• /
• pp.599-607
• /
• 2015

In this study, we theoretically investigate the thermal performances of heat pipes that have different nano-fluid properties. Two different types of nano-particles have been used: $Al_2O_3$ and CuO. The thermal performances of the heat pipes are observed for varying nano-particle aggregations and volume fractions. Both the viscosity and the conductivity increase as the volume fraction and the aggregation increase, respectively. Increasing the volume fraction helps increase the capillary limit in the well-dispersed condition. Whereas, the capillary limit is decreased under the aggregate condition, when the volume fraction increases. The dependence of the heat pipe thermal resistance on the volume fraction, aggregation, and conductivity of the nano-particles is analyzed. The maximum thermal transfer of the heat pipe is highly dependent on the volume fraction because of the high permeability of the heat pipe. For the proposed heat pipe, the optimum volume fraction of the nano-particle can be seen through 3D graphics.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.197-197
• /
• 2017

본 연구에서는 입자성 오염물질을 다량 함유하고 있는 초기강우 유출수를 처리하기 위한 수처리 시설로 고속복합응집장치를 개발하였다. 고속응집복합장치의 요소기술은 마이크로 버블, 급속교반장치(인라인믹서), 전기촉매를 이용한 부상촉진장치, 볼텍스 흐름 등으로 구성되며, 기술 원리는 응집제에 의해 오염물질을 응결, 응집, 부상시켜 스컴을 제거하는 일반 응집 원리와 유사하다. 본 기술의 특징은 교반, 혼화조, 응집제를 1개의 조에 컴팩트하게 구성하여 체류시간을 10분 이내로 단축하였고, 볼텍스(voltex) 흐름을 이용한 선회류와 루버홀 형태의 스크린을 적용하여 응집효과를 극대화하였으며, 플럭에 의한 막힘이 없이 스크리닝이 이루어질 수 있도록 하였다. 또한, 부상촉진장치(전기유도)를 이용해 응집 플럭의 부상효과를 상승시켰고, 감속기와 일체화된 내통스크린이 선회류와 반대 방향으로 회전하면서 볼텍스 흐름의 가속효과에 의한 스크린 폐색 방지 및 응집부상 효율을 향상시킬 수 있도록 설계하였다. 부상슬러지는 별도의 플럭 제거 설비 없이 스크린 내통 회전에 이용되는 감속기에 부착된 스컴 제거기에 의해 동시 제거가 가능하며, 응집부상 처리수는 장치 가장 바깥 외곽에 충진된 필터층에서 최종 여과되어 방류되도록 구성함으로서 모든 처리공정이 단일 장치 내에서 이루어지도록 구성하였다. 본 고속복합응집장치는 전체 규격 ￠ $1000{\times}2,000mmH$의 시제품이 제작되어 현재 시흥소재 매화저수지에서 성능평가를 실시하고 있다.

• The Journal of Information Technology and Database
• /
• v.3 no.2
• /
• pp.25-38
• /
• 1996

병렬 데이타베이스 소프트웨어 구조 중 공유 디스크 구조는 트랜잭션간의 병렬도 향상, 적재 균형 용이, 데이타 재할당 용이 등의 장점을 가지고 있어 병렬 데이타베이스 구조 중 가장 효율적인 성능이 기대되고 있다. 그러나 공유 디스크 구조는 동시성/응집성 제어를 위한 추가적인 메세지의 증가로 네트워크 트래픽이 증가되는 문제를 가지고 있으며 이러한 문제를 완화시키고자 하는 연구가 계속되고 있다. 본 논문에서는 공유 디스크 구조의 동시성/응집성 제어를 위한 추가적인 메세지를 감소시키는 기법을 제안하고, 기존 기법과의 비교를 위해 성능 모델을 제시하였으며, 이를 통한 시뮬레이션을 수행하여 성능을 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.2314-2320
• /
• 2015

MBR (Membrane Bio-Reactor) process is known to consume enormous energy to control membrane fouling. To solve this problem, electro-coagulation technique has been applied to MBR. A series of electro-coagulation was applied to activated sludge suspension under different current density condition. After the electro-coagulations, membrane filtration of the activated sludge suspensions was conducted to investigate the effect of electro-coagulation on the fouling. As current density increased 10 to 40A/m2, the total fouling resistance (Rc+Rf) decreased from 18 to 79%, showing that the electro-coagulation improved the membrane filtration efficiency. Both the organic concentration in bulk and the particles size distribution were not nearly changed before and after the electro-coagulation. The enhanced filtration efficiency might be due to the aluminum hydroxide generated from chemical precipitation, which can be acted as a dynamic membrane preventing a deposition of foulants on membrane surfaces.