• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.11 no.4
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• pp.19-33
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• 1982

Briquette ashes, one of important solid wastes in Korea, have relatively high compression strength in spite of their low density, and provide sufficient surface area and some adsorption capacity. Results of this research show that a fixed-film biological process using briquette ashes as media can accomplish BOD removal efficiencies in treating organic wastewaters such as alcoholic waste, diluted nightsoil and sewage , and formula can be derived to determine the effluent BOD concentrations by superficial or volumetric organic loadings. Settling tanks may be required because effluent SS concentration is deteriorated due to the SS in influent or due to the slough-off of slime layer on the media when briquette ashes are utilized for a long period.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.12
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• pp.886-892
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• 2011

In a study on THMs formation at the distribution facilities in Seoul water supply for past 3 years from 2007 to 2009, THMs production was increased from inlet to outlet during the process in water treatment plant. However, such increased THMs amount was very small compared to THMs production formed after pre-chlorination and post chlorination. Accordingly, this study is aimed to investigate the characteristics of water quality parameters of Han River related to THMs formation in 6 water treatment plants in Seoul. The results showed that THMs and other factors such as temperature (r = 0.539~0.846) and turbidity (r = 0.421~0.863) had positive correlation while THMs had negative correlation with pH (r = -0.613~-0.800) and algae (r = -0.582~-0.901). There is no correlation between THMs and $NH_3-N$. According to the factor analysis, generally metabolite and organic matter factor $X_1$ (pH, BOD, algae), and seasonal and natural factor $X_2$ (temperature, turbidity) played an important role in the formation of THMs. Multiple regression analysis for THMs formation showed significance of regression appeared in most water systems.

• The Journal of Engineering Geology
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• v.23 no.1
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• pp.1-17
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• 2013

It is sometimes necessary to change the location of the collection conduit, which is constructed in shallow sediments in a stream, if the concentrations of $Fe^{2+}$ and $Mn^{2+}$ become too high for water treatment. A total of nine wells, including four shallow wells with a depth of 3 m and five deeper wells with a depth of 6 m, were installed in the study area at Naeseong-cheon in Yecheon-gun. The change in hydrogeochemical features of groundwater and the concentrations of $Fe^{2+}$ and $Mn^{2+}$ were examined at the wells during 5 hours of pumping. As pumping was performed, the velocity of groundwater flow was increased around the pumping well and aeration conditions were developed to precipitate iron and manganese oxides in an oxidizing environment. In addition, the concentrations of $Ca^{2+}$ and $Cl^-$ at the pumping well were increased following the mixing of surface water and groundwater. It is suggested that the center region of the stream would be more suitable for a new collection conduit, considering the concentrations of $Fe^{2+}$ and $Mn^{2+}$ in groundwater and their reducing effect during pumping. The installation of a collection conduit based on field tests performed to ensure water quality enables a reduction in the construction and management costs at water treatment facilities.

• Korean Journal of Environmental Agriculture
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• v.1 no.1
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• pp.31-38
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• 1982

The water quality at the Nakdong River stream was surveyed for 3 years from 1978 to 1980 at quarterly intervals of January, April, June and October at 12 sites along the main stream from Sangju to Imhaejin and at 2 sites of Geumho and Nam River tributaries. The overall results are summarized as follows: 1) The levels of dissolved oxygen in the Geumho River tributary on the basis of three-year average were 0.7 ppm in January, 1.3 ppm in April, 4.0 ppm in July and 0.8 ppm in October. BOD concentrations in the same period were 91 ppm in January, 37 ppm in April, 6 ppm in July and 24 ppm in October. The water of Geumho River was so highly contaminated that the water seems to be unsuitable for any type of water use. 2) The relatively clean water in the upstream of the main Nakdong River was rapidly polluted by the highly contaminated water of Geumho tributary. That is, dissolved oxygen and BOD at Hwawon site right after junction of the tributary were 10.4, 8.8 ppm in January, 5.8, 6.5 ppm in April, 6.3, 3.2 ppm in July and 7.0, 5.3 ppm in October, respectively. The values of turbidity, ammoniacal nitrogen and electrical conductivity were also observed to be quite high.

• Journal of Korean Society of Forest Science
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• v.90 no.4
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• pp.513-523
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• 2001

This study was conducted to investigate influences of solifluction and sediment runoff on the stream water qualities during the spring season. The study sites were four points in the northeastern area of the Bukhansan National Park. And, field surveys were carried out in the spring of 1999, 2000 and 2001. The results of this study were summarized as follows; During the investigation period, the amounts of sediment caused by solifluction on stream side slopes in the downstream were 1.3~1.7 times as large as those in the upstream. The pH of sediment caused by solifluction was a potential influence on the pH of stream water. Amounts of dissolved $Cl^-$, $NO_3{^-}$ and $SO{_4}^{2-}$ in stream water were proportion to the average amounts of $Cl^-$, $NO_3{^-}$ and $SO{_4}^{2-}$ in the sediment caused by solifluction. In the spring, the average pH of stream water was lower than the first class of the river water quality standard because of increasing chemical concentration as well as the contents of anions($Cl^-$, $NO_3{^-}$ and $SO{_4}^{2-}$) in the spring season. Also, the average electrical conductivity of water in downstream was about 2.3-3.3 times higher than that in upstream. The amounts of anions($Cl^-$, $NO_3{^-}$ and $SO{_4}^{2-}$) of water in downstream were about 1.2~7.4, 1.1~3.9, 1.1~1.4 times higher than those in upstream, respectively. Therefore, these results showed that the water quality of downstream was worse than that of upstream. As a result of regression analyses, the linear and exponential equation of pH and water quantity was pH = 1.7926 ${\times}$ stream water quantity + 5.9577($R^2=0.46$), and those of electrical conductivity and water quantity was $EC=34.417e^{3.6334{\times}\text{stream water quantity}(m^3/sec)}$ ($R^2=0.44$).

• Journal of Korea Water Resources Association
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• v.57 no.3
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• pp.151-164
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• 2024

In water treatment plants supplying potable water, the management of chlorine concentration in water treatment processes involving pre-chlorination or intermediate chlorination requires process control. To address this, research has been conducted on water quality prediction techniques utilizing AI technology. This study developed an AI-based predictive model for automating the process control of chlorine disinfection, targeting the prediction of residual chlorine concentration downstream of sedimentation basins in water treatment processes. The AI-based model, which learns from past water quality observation data to predict future water quality, offers a simpler and more efficient approach compared to complex physicochemical and biological water quality models. The model was tested by predicting the residual chlorine concentration downstream of the sedimentation basins at Plant, using multiple regression models and AI-based models like Random Forest and LSTM, and the results were compared. For optimal prediction of residual chlorine concentration, the input-output structure of the AI model included the residual chlorine concentration upstream of the sedimentation basin, turbidity, pH, water temperature, electrical conductivity, inflow of raw water, alkalinity, NH₃, etc. as independent variables, and the desired residual chlorine concentration of the effluent from the sedimentation basin as the dependent variable. The independent variables were selected from observable data at the water treatment plant, which are influential on the residual chlorine concentration downstream of the sedimentation basin. The analysis showed that, for Plant, the model based on Random Forest had the lowest error compared to multiple regression models, neural network models, model trees, and other Random Forest models. The optimal predicted residual chlorine concentration downstream of the sedimentation basin presented in this study is expected to enable real-time control of chlorine dosing in previous treatment stages, thereby enhancing water treatment efficiency and reducing chemical costs.

• Membrane Journal
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• v.18 no.2
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• pp.157-167
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• 2008

Removal of organic substances and taste/odor control are ones of the main issues in water supply, resulting in introduction of advanced processes such as ozon/GAC, or PAC. However, raw water quality deteriorates, new pollutants advent, so water quality is not acceptable enough even with those existing advanced processes. In this paper, a new advanced water treatment process using PAC slurry blanket, where PAC particles stay in the basin as slurry blanket, coupled with submerged membranes is introduced. A pilot plant $(80m^3/day)$ was installed to assess the performance of this new process using actual raw water, and DOC was removed higher than 90% in the beginning and $70{\sim}80%$ afterwards, while 2-MIB and geosmin were removed completely. This new process still requires future study on process optimization and long-term assessment, however it seems highly possible to countermeasure as a new advanced process with high removal efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2205-2213
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• 2000

To investigate removal efficiency of dissolved matter by NF and RO, a pilot plant was operated for six months using groundwater treated by UF membrane. After the pilot plant operation, we performed autopsy test to identify characteristics of foulant attached on the membrane surface applying the used NF and RO in the pilot plant test. In autopsy test, we measured permeate flux and recovery rate of flux by chemical cleaning in each membrane. We also analyzed chemical cleaning disposal to examine component of foulant. Permeate flux of NF and RO1 showed rapid decline after 100 days of operation. Especially, reduction of specific flux in RO1 was more serious than in NF. Specific flux of RO2 with a low recovery rate resulted in gradual flux decline. Removal efficiencies of dissolved inorganic matters as a conductivity were 76.3%, 88.2% and 95.3% respectively for NF, RO1 and RO2, and RO2 presented the highest removal efficiency. And those of dissolved organic matters as TOC were about 80% for both NF and RO. The specific flux of membranes declined gradually from the feed water inlet to outlet of the membrane module and it showed that membrane fouling increased along the feed flow direction. Namely, concentration of pollutants became higher and volume of feed water was less as the feed flow approached to the outlet. It seemed that major foul ants were Ca consolidated into inorganic material and Si consolidated into organic material on the membrane surface. Fe was a great contribution to irreversible fouling. The SEM results indicated that the organic matter was attached to the first layer, closer to the membrane, and then inorganic matter with tetragonal shape layered over them. We could not observe biofouling because microorganism, which was cause of biofouling, was almost pretreated in UF membrane.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.1
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• pp.45-53
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• 2008

In this paper, the property of influent water and variations of removal efficiencies in each unit processes were studied based on the experiment data from the advanced water treatment plant in a city of Korea. The microbial species in the biological activated carbon(BAC) after backwashing of activated carbon filtration tank(ACFT) were also identified. The property and the removal efficiencies were evaluated by considering 8-9 items. The variations of 4 items were investigated from the influent and effluent of ACFT. SEM recording were conducted on BAC samples before and after backwashing. And the existence of attached microorganisms were identified through HPC(Heterotrophic Plate Counter) investigation. For the property of influent water, the concentrations of most items were maintained in the constant ranges, some items had seasonal properties. For the removal efficiencies, there were some items showing similar monthly-pattern and increasing with time, other items decreasing at the ozone contactor. Through these investigations, it was possible to distinguish the target items, which were removed by the advanced processes. The existence of microorganisms in ACFT could be predicted based on the variation curve of NH$_3$-N, and this fact were proved by SEM and HPC.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.859-863
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• 2008

축산폐수, 침출수 등의 고농도 폐수를 생물학적으로 처리할 경우 최종 방류수는 강한 색도를 띠며 고분자량의 유기물질을 다량 함유한다. 이는 생물학적으로 분해하기 어려운 유기성 복합체와 생화학적 반응에 의한 중간생성물로 색도를 띠는 천연유기물질(NOM)을 포함한다. 생물학적 처리수의 색도는 심미적인 불안감, 방류수역의 수질오염 및 공중보건상의 잠재적 위해성을 갖는다. 또한, 수자원 이용측면에서 정수처리공정에서의 약품투입량 증가와 특히, 소독부산물 생성이라는 잠재적 문제점이 뒤따른다. 따라서 이러한 문제점을 해소하기 위한 생물학적 2차 처리수의 후속처리가 요구되며, 실제로 난분해성 유기물과 색도를 제거하기 위한 흡착, 막 분리, 고급산화(AOP) 및 화학적 응집 등의 물리-화학적 공정에 대한 연구가 수행되어왔다. 특히, 화학적 응집은 무기응집제 또는 고분자중합체(Polymer)를 이용하여 콜로이드성 입자와 색도를 띠는 난분해성 유기물을 전기적 불안정화를 유도함으로서 흡착 및 응집과정을 통해 제거하는 공정으로 많은 연구자들에 의해 연구되어왔다. 그러나 난분해성 유기물과 색도제거는 대상원수의 성상과 화학적 특성 등에 따라 각각의 제거효율과 최적 운전조건이 상이하게 나타난다. 화학적 응집공정은 비교적 높은 제거효율을 보이지만, 운전 및 유지관리의 기술적 어려움, 경제적 비효율성 등으로 인하여 적용에 어려움을 겪고 있는 실정이다. 본 논문에서는 생물학적 혐기-호기성 공정에서 방류되는 축산폐수의 2차 처리수를 대상으로 화학적 응집에 의한 색도 및 난분해성 유기물의 제거거동을 고찰하였다. 대상 처리수의 $TCOD_{Cr}$ 농도는 평균 410 mg/L인 반면, $BOD_5$는 7-15 mg/L 범위로 난분해성 유기물을 다량 함유하고 있음을 알 수 있었다. 이에 황산알루미늄(Aluminium sulfate; $Al_2(SO_4){\cdot}14H_2O$)과 염화철(ferric chloride)의 무기응집제를 이용하여 자 테스트(jar test)를 수행한 결과, 동일한 응집제 주입량에서 염화철의 유기물 제거 효율이 높은 것으로 나타났다. 황산알루미늄과 염화철의 경우 각각의 응집제 주입율 5.85mM에서 89%, 7.03mM에서 97.5%의 최대 유기물 제거효율을 보여주었으며, 이 때 최종 pH는 4.0-5.6 범위이었다. 한편, 대상 원수 내의 콜로이드성 입자 또는 용존성 유기물의 작용기(functional group)는 일반적으로 음으로 하전 되어 있어 응집에 의해 잘 제거되지 않는 특성을 가지고 있다. 따라서 과량의 응집제를 주입하여 다가의 양이온성 금속염을 흡착시켜 전기적으로 중화시키고, 생성된 침전성 수화물 내에 포획 또는 여과시켜 제거하게 된다. 이 때, 금속염 수화종의 전하밀도가 응집효율에 영향을 주는 것으로 알려져 있는데, 다가의 양이온은 전기적 이중층(Double layer) 압축에 의한 불안정화를 향상시킬 수 있기 때문에다. 또한, 2가 금속염은 색도유발물질과 흡착하여 humate 또는 fulvate 등의 착화합물(complex)을 형성시켜 응집효율을 향상시킬 수 있다. 따라서 본 연구에서는 생물학적 2차 처리수의 화학적 응집처리에 있어서 알루미늄염 등의 다가이온 첨가가 응집에 미치는 영향을 관찰하고, 후속되는 플록형성 및 침전공정에 의한 제거효율을 비교, 평가함으로써 2차 처리수로부터 난분해성 유기물과 색도를 보다 효과적이고 경제적으로 제거할 수 있는 최적인자를 도출하고자 하였다.