• Korean Journal of Soil Science and Fertilizer
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• v.45 no.4
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• pp.642-648
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• 2012

To evaluate the water quality in Juksancheon constructed wetlands for treating non-point source pollution, the removal rates of nutrients in water and the total amounts of T-N and T-P uptakes by water plants were investigated. Chemical characteristics of T-N and T-P in sediment were investigated. The concentrations of BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), SS (Suspended Solids), T-N and T-P in inflow were 0.07~1.47, 0.60~2.65, 0.50~4.60, 1.38~6.26 and $0.08{\sim}0.32mg\;L^{-1}$, respectively. The removal rates of BOD, COD, SS, T-N, and T-P were -10, 51, 66, -3 and 5%, respectively. The maximum amount of T-N uptake by water plants in August was $368.7mg\;plant^{-1}$ in the $2^{nd}$ treatment stage by Nymphoides peltata, $1314.6mg\;plant^{-1}$ in the $3^{rd}$ treatment stage by Iris pseudacorus, $1160.4mg\;plant^{-1}$ in the $4^{th}$ treatment stage by Nymphaea tetragona GEORGI, respectively. The maximum amount of T-P uptake by water plants in August was $121.7mg\;plant^{-1}$ by Nymphoides peltata in the $2^{nd}$ treatment stage, $268.7mg\;plant^{-1}$ by Iris pseudacorus in the $3^{rd}$ treatment stage and $212.0mg\;plant^{-1}$ by Nymphaea tetragona GEORGI in the $4^{th}$ treatment stage, respectively. Organic matter contents in sediments were not different. Contents of T-N and T-P in sediments were higher in spring. Microbial biomass C:N:P ratios in sediments in spring, summer, autumn and winter were 117~140:1~4:1, 86~126:5~6:1, 68~101:2~6:1 and 47~138:2~4:1, respectively. We could conclude that Juksancheon constructed wetlands show high removal efficiencies of COD and SS. However, improvements of management in winter season should be considered to improve the removal efficiencies of pollutants.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.260-267
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• 1998

This experiment used the enclosed bench-scale reactors of 242 liters was conducted to obtain basic data on temporal and spatial variations in temperature, oxygen and moisture content, which were important factors of biological activities, during composting of mixture of dairy manure and rice straw. The reactors with thermocouples, oxygen sensor and datalogger were aerated at four different rates of 0.09, 0.18, 0.90 and 1.79 l $min^{-1}kg$ dry $solids^{-1}$. The higher aeration rates were, the faster the rates of increase and decrease in composting temperature were in both of initial and turnover stage, and the smaller the temperature difference between exhaust air and composting materials. Composting temperature of initial stage increased suddenly in all aeration rates, then stationary phase of temperature in materials and exhaust air showed at $50{\sim}53^{\circ}C$ for 5 hours and at $45^{\circ}C$ between 5 and 15 hours, respectively. In initial stage the maximum temperature was decreased with increasing aeration rates but in the stage after turnover it was the opposite except for 1.79 l $min^{-1}kg^{-1}$. Time arrived at the maximum temperature of composting materials was later in low-aeration rates than high-aeration rates at both stages. Time maintained high-temperature more than $45^{\circ}C$ was rapidly decreased with increasing aeration rates. In initial stage of composting maintaining time of $65^{\circ}C$ or more was the longest in the treatments of 0.09 and 0.18 l $min^{-1}kg{-1}$, while those of $55{\sim}65^{\circ}C$ and $45{\sim}55^{\circ}C$ was in 0.90 and 1.79 l $min^{-1}kg{-1}$, respectively. The minimum oxygen content and the maximum oxygen consumption rate in exhaust air through composting materials showed the increased trends with increasing aeration rates. In initial stage the minimum oxygen content was ranged from 0.9% to 7.4% for 32 to 59.5 hours and the maximum oxygen consumption rate was $1.89{\sim}6.48$ $gh^{-1}kgVS^{-1}$. In the stage after turnover their levels were $2.1{\sim}19.9%$ and $1.76{\sim}3.49 %$g/h-㎏ VS, respectively, for 16 to 49.5 hours.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.495-504
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• 2017

An amphibious scrubbing/suction dredging machine with cylindrical rotating brush, housing, and turbidity barrier was newly-developed to remove both sediments with about 10 cm thickness and periphyton attached on various structures in urban water-circulating systems through the scrubbing, suction, and dredging processes. Based on the field application and long-term monitoring, the increase in both suspended solids (SS) and turbidity of water during the scrubbing, suction, and dredging processes was negligible (p>0.05). In some cases, the turbidity of water initially increased, however, the turbidity was stabilized within 20 minutes from the start of dredging processes. The concentration changes in TN and TP of water were not statistically different (p>0.05) before and after the scrubbing, suction, and dredging processes, indicating that benthic nutrients released from sediments were not significantly diffused, and were not supposed to cause significant water pollution. Also, water treatment facilities along with an amphibious scrubbing/suction dredging machine could be more effective since the removal of contaminant loadings through the scrubbing, suction, and dredging processes was much greater than that through simple coagulation/precipitation processes. Finally, GPS-based realtime tracking and operation program have been developed and applied in various urban water-circulating systems, and development of driver cooperative autonomous driving system is in progress to eliminate the need for manual driving of an amphibious scrubbing/suction dredging machine.

• Journal of the Mineralogical Society of Korea
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• v.18 no.4 s.46
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• pp.301-312
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• 2005

The present study investigated the physical changes and reaction products with setting time after mixing of various mineral admixtures such as lime, hydrated lime, gypsum, kaolin, zeolite and diatomaceous earth with four types of cement (portland cement, slag cement, quick lime, hydrated lime) and clay rich sediments in soft foundation. As results, slag cement showed the greater compressive strength than normal portland cement. The mixing experiments with various mineral admixtures and slag cement resulted that gypsum showed the greatest compressive strength. Additionally, we conducted mixing experiments with various mixing ratios of gypsum and slag cement. The experiments showed that the mixing ratio of $30\%$ gypum and $70\%$ slag cement has the greatest compressive strength. Ettringite was produced as a reaction Product. This fact indicates that gypsum effectively promotes hydration reaction and contributed to the greater compressive strength. These experimental results can be used as fundamental data for the stabilization of soft clay foundation.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.220-220
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• 2020

영산강수계는 상류에 4개의 농업용 댐이 위치하여 환경대응용수 확보 및 하천유지유량이 절대적으로 부족하고, 갈수기 하천 유량의 약 67 %가 광주 제 1, 2 하수처리장 방류수가 차지하고 있어 하천의 수질과 수생태계를 위협하고 있다. 이에 최근에는 오염된 하천의 건강성을 회복하기 위한 방법으로 수생태계의 정화능력을 활용한 인공습지가 각광받고 있다. 영산강 유역에서도 자연의 정화능력을 활용하여 하천 오염원을 저감시키기 위한 사업의 일환으로 2016년 광주 제 2 하수처리장 방류구에 서창오미공원 습지를 조성하였다. 이 습지는 유입량이 적어 정상적 기능이 어려운 기존 습지를 재조성한 것으로 하수처리장 방류수 약 5만 ㎥/day을 습지로 유입시켜 수질정화용 식재식물을 이용하여 하수처리장 방류수 수질을 개선한 사업이다. 2016~2017년 모니터링 결과, 습지 유입 전·후 BOD는 평균 33.5 %, 최대 73.1 % 저감 되었으며, T-P 또한 평균 59.3 %, 최대 91.6 % 저감 되었다. 그러나 습지는 운영기간 경과 시 퇴적물 축적, 고사체로 인한 T-P 용출 등으로 인하여 처리수의 수질이 더 악화될 우려가 있기 때문에 습지 조성 후 지속적인 유지관리와 모니터링이 필요하다. 그 예로 하수처리장 방류수와 비점오염원 처리를 위해 주암호에 조성된 인공습지의 경우, 2001년 준공 후 지속적인 관리 및 모니터링을 통하여 약 17년이 지난 2018년에도 BOD 49.3 % T-N 65.1 %, T-P 19.2 % 로 저감되어 오염원 및 영양염류 제거에 큰 효과가 있는 것으로 나타났다. 따라서 본 조사에서는 서창오미공원과 주암호 인공습지 운영 결과를 토대로 습지 모니터링의 중요성과 적정 운영 방안을 제시하고자 하며, 영산강 하천의 점·비점오염원 저감을 위한 신규 인공습지 조성 사업에 기초자료로 활용하고자 한다.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.15-26
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• 2003

Ultrasonic inspection methods are widely used for detecting flaws in materials. The signal analysis step plays a crucial part in the data interpretation process. A number of signal processing methods have been proposed to classify ultrasonic flaw signals. One of the more popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature space. This paper describes an alternative approach which uses the least mean square (LMS) method and expectation maximization (EM) algorithm with the model based deconvolution which is employed for classifying nondestructive evaluation (NDE) signals from steam generator tubes in a nuclear power plant. The signals due to cracks and deposits are not significantly different. These signals must be discriminated to prevent from happening a huge disaster such as contamination of water or explosion. A model based deconvolution has been described to facilitate comparison of classification results. The method uses the space alternating generalized expectation maximization (SAGE) algorithm In conjunction with the Newton-Raphson method which uses the Hessian parameter resulting in fast convergence to estimate the time of flight and the distance between the tube wall and the ultrasonic sensor Results using these schemes for the classification of ultrasonic signals from cracks and deposits within steam generator tubes are presented and showed a reasonable performances.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.235-241
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• 2003

The effect of ultraviolet (UV) radiation on the characteristics of algae-derived dissolved organic matter (DOM) was examined by comparing the biodegradability and DOM fraction distribution of algal DOM before and after UV exposure. Algal DOM from two axenic cultures of Microcystis aeruginosa and Oscillatoria agardhii were irradiated for 24 h at a UV intensity of 42 W/$m^2$. A complete degradation of algal DOM during the UV exposure did not occur, remaining at constant concentrations of dissolved organic carbon(DOC). After UV exposure, however, microbial degradations were reduced by 17% in M. aeruginosa and 53% in O. agardhii, respectively, and decomposition rates also were two times lower in UV exposed algal DOM. In addition, the chemical compositions of algal DOM altered substantially after UV radiation exposure. The proportions of hydrophilic bases (HiB; protein-like DOM) decreased considerably in both algal DOM sources after UV exposure (16.8% and 20.0% of DOM, respectively), whereas those of hydrophilic acids (HiA; carboxylic acids-like DOM) increased as much as the decrease of the HiB fraction. Capillary ion electrophoresis (CE) analysis showed that several carboxylic acids increased significantly after UV exposure, further confirming an increase in HiA fractions. The results of this study clearly indicate that algal DOM can be changed in its chemical composition as well as biodegradability without complete degradation by UV radiation.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.50-58
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• 1995

These studies were carried out to develop a system for non -destructive and continuous measurement of fresh weight and to analyse the growth response of leaf lettuce under the different nutrient solution and light condition with this system. The developed measurement system was consisted of four load cells and a microcomputer. The output from the system was highly positive correlation with the plant fresh weight above the surface of the hydroponic solution. The top fresh weight of plant could be measured within the error $\pm$ 1.0g in the range of 0 - 2000g. The top fresh weight of leaf lettuce increased 44 times at 18th day after transferring to the nutrient solution, and the maximum growth rate was observed at 13th day after transferring. The growth rate was 10.7- 29.6% per day during 18 days. Optimum concentration of the nutrient solution for the growth of lettuce was 1.4 - 2.2 mS/cm of EC level. When the light condition was changed from dark to light, the fresh weight was temporarily decreased, but the fresh weight increased under the opposite condition. Top fresh weight of leaf lettuce in the darkness normally increased within 12 hours after darkness treatment, and then slowly increased until 78 hours under continuous dark condition. After that times, the fresh weight began to decrease.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.125-125
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• 2016

남강 권역은 5개의 단위유역으로 구성되어 있으며, 남강A, 남강B, 남강C, 남강D와 남강E로 명명되고 1단계 수질오염총량관리제도 시행 이후 유역 내 개발 등으로 인한 오염원이 증가하고 장기간 퇴적된 저니층으로부터 오염물질이 용출되는 등 수질의 자정능력보다 더 많은 오염물질이 수체내로 유입됨으로써 수질이 악화되자 수량확보 뿐만 아니라 남강의 수질관리에 대해서 관심을 가지기 시작하였다(GNDI, 2010). 남강 하류수계는 하상구배가 매우 완만하며 유속이 느리다. 따라서 물의 체류시간이 호수와 비슷한 양상을 보이고 있다. 더욱이 남강 하류수계는 주변의 도시와 농경지로부터 물의 소모량이 크기 때문에 하류수계의 물의 흐름이 더욱 완만해지고 이로 인하여 수질 악화가 가속화되고 수역의 영양단계가 점점 증가하는 부영양화현상이 발생되고 있다. 남강하류수계와 같이 부영양화 된 수계내의 미처리 된 영양염을 이용한 식물플랑크톤의 생산에 의해 자생BOD가 공급된다. 따라서 남강댐 하류지역과 같은 수리 수문학적 특징을 가진 유역은 수질관리를 위해서 특정 수역에 유입 BOD와 자생 BOD가 어느 정도 기여하는가를 정량적으로 파악한 후, 기여도에 따라 오염원인 물질을 줄이기 위한 수질관리 방안이 설정되어야 한다. 본 연구에서는 남강유역의 오염원의 기여율 분석을 위해 하천수질모델인 QUALKO2를 사용하였으며, 점오염원 뿐만 아니라 수질에 상당한 영향을 끼치는 비점오염원의 영향을 통합적으로 고려하기 위하여 유역 모델인 SWAT과의 연계방안을 제시하였다. 또한 모델의 연계 적용을 통해 산정된 내부오염원과 내부오염원의 기여율과 수질측정결과를 활용하여 분석한 기여도와의 비교를 수행하여 신뢰성을 확보하였다.

• Journal of Biosystems Engineering
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• v.9 no.1
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• pp.62-70
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• 1984

가축배설물(家畜排泄物)의 콤포스트화(化) 작업(作業)의 공학적(工學的)인 국면(局面)은 축산(畜産) 경영(經營)의 축산물(畜産物) 생산성(生産性), 에너지 보전(保全), 공해방지(公害防止)와 분뇨처리(糞尿處理)의 노력(勞力) 절약(節約)에 긴밀(緊密)한 관계(關係)가 있다. 그러나 우리나라에 있어서 축산업(畜産業)의 사양(飼養) 규모(規模)와 두수(頭數)는 매년(每年) 증가(增加)하고 있는 경향(傾向)인바 전통적(傳統的)인 가축(家畜) 배설물(排泄物) 처리(處理) 및 재이용(再利用) 과정(科程)에서 발생(發生)되는 문제점(問題點)에 대(對)한 연구(硏究) 자료(資料)가 없고 특(特)히 콤포스트화(化) 작업(作業)이 원시적(原始的)이므로 개선(改善) 확립(確立)이 절실(切實)히 요구(要求)되는 실정(實定)이다. 본(本) 연구(硏究)의 목적(目的)은 가축(家畜) 분뇨(糞尿)의 콤포스트화(化) 작업(作業) 과정(科程)에서 공학적(工學的)인 제(諸) 문제점(問題點)을 조사(調査) 분석(分析)하여 현상(現狀)을 평가(評價)하고 개선(改善) 방안(方案)을 모색(摸索)하기 위한 기본자료(基本資料)를 제공(提供)하고져 수행(遂行)하였다. 이에 관한 조사(調査)와 분석(分析) 결과(結果)를 요약(要約)하면 다음과 같다. 1. 축산농가(畜産農家)의 가축(家畜) 배설물(排泄物) 처분(處分) 방법(方法)은 대부분(大部分)이 자연건조(自然乾燥), 퇴적(堆積), 혐기적(嫌氣的)인 고형(固形) 또는 액상(液狀) 퇴비화(堆肥化)에 의하여 실시(實施)되고 있었으며 가축분뇨(家畜糞尿)로 인(因)한 공해(公害)는 심각(深刻)하다는 것을 알 수 있었다. 2. 호기성(好氣性) 야적(野積) 콤포스트의 통기작업(通氣作業)은 트랙터에 부착(附着)되어진 전후(前後) 작동식(作動式) 로우더가 바람직하다. 3. 농축산(農畜産) 폐기물(廢棄物)의 콤포스트화(化) 작업(作業)은 축산농가(畜産農家)를 중심(中心)으로 한 콤포스트 센타에서 전체 농가(農家)가 지방(地方) 증진(增進)과 오염(汚染) 방지(防止)를 하기 위해 참여(參與)하여 완전(完全) 공동(共同) 이용(利用) 체계에 따라 일관성(一貫性)있게 수행(遂行)되어야 한다. 4. 호기성(好氣性) 야적(野積) 콤포스트 작업(作業)은 다른 방법(方法)에 비하여 운영비(運營費)가 적게 들어 영세적(零細的)인 축산업(畜産業)의 경우(境遇)에 가장 적당(適當)하고 공해(公害)를 방지(防止)함으로서 한국(韓國) 축산농가(畜産農家)의 콤포스트화(化) 시설(施設)로 전망(展望)이 밝다고 판단(判斷)된다.