Objectives of this study were to identify the hotspot for displacement of the on-line water quality sensors, in order to detect illicit discharge of untreated wastewater. A total of twenty-six water quality parameters were measured in sewer networks of the industrial complex located in Daejeon city as a test-bed site of this study. For the water qualities measured on a daily basis by 2-hour interval, the self-organizing maps(SOMs), one of the artificial neural networks(ANNs), were applied to classify the catchments to the clusters in accordance with patterns of water qualities discharged, and to determine the hotspot for priority sensor allocation in the study. The results revealed that the catchments were classified into four clusters in terms of extent of water qualities, in which the grouping were validated by the Euclidean distance and Davies-Bouldin index. Of the on-line sensors, total organic carbon(TOC) sensor, selected to be suitable for organic pollutants monitoring, would be effective to be allocated in D and a part of E catchments. Pb sensor, of heavy metals, would be suitable to be displaced in A and a part of B catchments.

낙동강 하구에서 연속관측 자료를 바탕으로 담수의 방류와 수온 및 염분의 시간에 따른 반응을 조사하였다. 낙동강 하구 서쪽 해역에 계류형 센서를 설치하고 2017년 4월 1일부터 2018년 3월 31일까지 10분 간격으로 수온과 염분을 측정하였다. 담수의 방류량은 평상시에 200 m3 s-1 d-1 이하로 유지되었으나, 풍수기에는 500 ~ 1000 m3 s-1 d-1 이상의 많은 양의 담수가 빈번하게 방류되었다. 담수의 방류는 대조기에는 간조를 전후하여 발생하였고, 소조기 동안에는 계속적으로 일어났다. 평상시에 수온과 염분은 소조기 동안 큰 변동 없이 안정 되는 경향을 보이는 반면에, 대조기에는 방류주기에 따라 규칙적인 변동을 나타내었다. 연구기간 동안 염분은 평균 29이었으며, 평상시에 염분 농도는 평균 이상으로 유지되었고 일시적인 감소 이후에도 빠르게 회복되었다. 풍수기에는 약 3개월 동안 평균 이하의 저염환경이 지속되었다. 이러한 결과는 담수의 방류량뿐만 아니라 방류의 지속시간과 대량 방류의 빈도가 낙동강 하구의 표층 수온과 염분의 변동성에 영향을 미치는 중요한 요인이 된다는 것을 의미한다.

산업 발전에 따른 물 사용량과 폐수 배출량의 증가로 환경오염에 대한 사회적 인식과 제도적 개선에 대한 관심이 높게 부각되고 있으며, 기후 변화로 가뭄 빈발과 지역적 물 부족 문제를 해결하기 위한 대안으로 물 재이용 시스템 공급을 활성화시키는 것이다. 해당 사업장내 하(폐)수의 재이용 시스템 도입에 대한 제반 여건은 기술적으로는 상당 수준으로 정착되고 있으나 물 재이용 시스템에서 발생되는 오염원 배출에 대해서는 여전히 환경 보전 및 수자원 보호 등의 사회적 책임과 기술적 한계로 인하여 물 재이용 시스템 활성화에 난항을 겪고 있다. 이에 발생 폐수를 당해 사업장안에서 재이용하고 오염원은 고형화하여 외부 처리하는 폐수 무방류 배출시설의 도입에 대해 실적 사례 소개와 하수 재이용 시스템과의 연계성에 대해 소개하고자 한다.

Vortex tubes are simple tubes that can separate hot and cold air from compressed air without any internal device configuration and are used in many industries. If the vortex tube with these advantages is applied to an air conditioning system, it will be free from the use of refrigerant. In this study, basic study on discharge flow rate and temperature separation characteristics was carried out by varying the number of generator nozzle hole in various shapes of the vortex tube according to the inlet pressure of the vortex tube. Experimental results show that as the number of nozzles increases, the discharge flow rate tends to decrease and the temperature separation characteristics were excellent in the number of nozzles 6~7.

Stream of afterglow of an atmospheric pressure plasma can conveniently be used for large scale decontamination operations. In the present study, an afterglow dielectric-barrier discharge air plasma (ADDAP) was used to inactivate Escherichia coli O157:H7 as a model microorganism for studying the plasma inactivation effect. The plasma was generated at current levels in the range of 0.4 - 0.8 A. The power consumption of ADDAP generation system ranged 169.5 - 221.9 W with respect to the current intensity range. At this current level, the temperature observed in the treatment chamber remained less than 30℃. Regarding chemical composition of ADDAP in the treatment chamber, NOx species were predominantly generated. The levels of NOx species increased as the current intensity increases and the maximum NO and NO2, concentrations noted were 6 and 4 ppm, respectively, but that of CO was less than 1 ppm level at 0.8 A. Upon treating with the ADDAP generated at 0.4 - 0.8 A for 180 min, E. coli O157:H7 showed 1.24 – 2.71 log reductions. The inactivation patterns exhibited better fit to Weibull-tail model. The comparison of delta values indicated that superior inactivation effects were observed as the current intensity increased.

Residual detergents and surfactants on utensils have brought about health issues because they can be absorbed to human digestion system together with containing foods. In the present study, a dielectric barrier discharge plasma (DBDP) was used to explore the applicability of non-thermal plasma for the degradation of residual surfactants and dishwashing detergents in order to reduce the intake of the residues remaining on utensils as the result of incomplete rinsing during dishwashing procedures. DBDP was generated at current intensity 2.0 - 3.0 A, and electrode gap 2.5 mm. Diluted dishwashing detergents and surfactants were spotted on slide glasses and exposed to DBDP for different periods of time. The results indicated that the dishwashing detergents and surfactants were degraded by 46.9 - 84.3% after up to 120 min treatments. Weibull equation was the best fit model to the degradation patterns of surfactants, and the decimal degradation time(δ) of 180.2 - 688.9 min were observed according to currents. Surfactants contained in detergents were degraded more effectively than the surfactants themselves. Among the anion surfactants, DDBS was more rapidly degraded than LAS and ABS.

Al2O3-SiC ceramic composites are produced using pressureless sintering, and their plasma resistance, electrical resistance, and mechanical properties are evaluated to confirm their applicability as electrostatic-discharge-safe components for semiconductor devices. Through the addition of Mg and Y nitrate sintering aids, it is confirmed that even if SiC content exceeded 10%, complete densification is possible by pressureless sintering. By the uniform distribution of SiC, the total grain growth is suppressed to about 1 μm; thus an Al2O3-SiC sintered body with a high strength over 600 MPa is obtained. The optimum amount of SiC to satisfy all the desired properties of electrostatic-discharge-safe ceramic components is obtained by finding the correlation between the plasma resistance and the electrical resistivity as a function of SiC amount.

Desalination plants have been recently constructed in many parts of the world due to water scarcity caused by population growth, industrialization and climate change. Most seawater desalination plants are designed with a submarine pipeline for intake and discharge. Submarine pipelines are installed directly on the bottom of the water body if the bottom is sandy and flat. Intake is located on a low-energy shoreline with minimal exposure to beach erosion, heavy storms, typhoons, tsunamis, or strong underwater currents. Typically, HDPE (High Density Polyethylene) pipes are used in such a configuration. Submarine pipelines cause many problems when they are not properly designed; HDPE pipelines can be floated or exposed to strong currents and wind or tidal action. This study examines the optimal design method for the trench depth of pipeline, analysis of on-bottom stability and dilution of the concentrate based on the desalination plant conducted at the Pacific coast of Peru, Chilca. As a result of this study, the submarine pipeline should be trenched at least below 1.8 m. The same direction of pipeline with the main wind is a key factor to achieve economic stability. The concentrate should be discharged as much as high position to yield high dilution rate.