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토양치료 기술의 한계점들이 더욱 명백해지고 그 분야의 실행과 효율에 있어서 더 맡은 비용이 소요되기 때문에 구조적인 기술선택공정의 개발에 많은 촛점이 모아지고 있다. 이상적으로 이러한 선택공정은 가장 비용면에서 효율적인 기술을 만들어내야 하며 이 기술은 단기간 내에 정화목표를 달성할 것이다. 실험실 적용성 연구들이 이러한 공정의 기본적인 구성성분을 포함한다 하더라도 설계, 실행, 그리고 그 결과들을 평가하는 방법론에 관해서는 거의 논의된 바가 없다. 본 논문은 기술선택에서의 적용성 결과들을 사용하는 환경전문가 또는 그런 연구를 실행하는 다른 이들을 위한 실제적인 이해를 제공한다. 토양정화를 위한 처리기술의 선별과 평가를 위한 전반적인 절차는 다음과 같은 4단계로 집약되며, 하나의 기술적 입장으로부터 어떤 개선 계획을 대개 다음의 분명한 4단계로 이루어진다.; 제 1 단계 : 기술 선별과 선택 제 2 단계 : 선택된 기술의 조사 제 3 단계 : 파이롯/현장 연구 제 4 단계 : 기술 평가 본 논문의 주된 촛점은 제 1, 2 단계에 있다. 제 1 단계에서는 Step 1∼Step 6 를 단계적으로 나뉘어 있으며 공정을 선별하고 선택하는 제 1단계의 세가지 기본 구성성분을 흙과 지하수의 특성규명, 흡착, 실험, 생물분해실험 이다. 제 2 단계는 벤치스케일 실험으로서 주어진 개선기술의 효율성을 평가하고 적절한 설계인자들을 적용할 수 있는 자료를 생성하는 것이 1차적인 목표이고, 2차목표는 각 토양의 특성에 의해 영향을 받을 수 있는 동력학적 매카니즘과 예비 경제분석을 포함한다. As the limitations of site remedial technologies become more apparent and greater experience in their field implementation and effectiveness is gained, increased emphasis is placed on development of a structured technology selection process. Ideally, this selection process should yield the most cost-effective technology, which will accomplish cleanup goals in the shortest time frame. Although laboratory treatability studies comprise an essential component of this process, very little has been written about the methodology of designing, executing, and assessing the value of their results. This article presents practical considerations for environmental professionals who use treatability results in technology selection or others who execute such studies. As more and more site remediation technology are developed and implemented at different application scales, a large body of performance data is becoming available. An important conclusion can be drawn that technology performance data, for the most part, are not transferable from one site to another. Each site has its own unique characteristics that make direct transfer of technology performance data from other sites risky and thus undesirable. Such characteristics are numerous and sometime their effect is not so obvious. They include soil type; mineralogical, physical, and chemical properties: prevailing geohydrology; extent and degree of heterogeneity; groundwater chemistry; type of contaminants and their concentration: age of the spill or discharge: and climatic conditions. Due to the inadvisability of directly transferring technologies from one site to another, the need arises for a structured approach to the selection of the most appropriate technology for each individual site. Laboratory treatability studies are a major component of such an approach, especially when dealing with sites contaminated with complex wastes, such as mixtures of organics and heavy metals. In general, the objectives of a treatability study are to screen various treatment techniques, investigate the physicochemical and/or biological mechanisms responsible for treatment, perform a sensitivity analysis of the technique, assess its feasibility and applicability, and derive design parameters for scale-up. In order to meet these objectives, the study's design and execution should follow a well-devised protocol. This not only provides quality control but also helps users of the study make useful interpretations of the results. The cost of conducting treatability studies is usually a very small portion of the total cost to clean up a site. However, the intonation obtained from such studies can result in substantial overall project cost savings and may drastically decrease the likelihood for failure. Although the cost savings component of treatability studies had often been overlooked in the past, treatability studies are now gaining widespread recognition for their ability to recuce overall project expenses.
The purpose of this study was to investigate the peeling percent, EIS, and neutralization degree of the inner lining and outer coating materials used to protect large diameter steel pipe or cast iron pipe from corrosion. And the service life of the inner lining and outer coating materials were predicted. The results are as follows. First, the peeling percent of the coal-tar enamel lining was estimated to be more than 10% after the age of 15 years or 19 years. And the electro impedance spectroscopy(EIS) was predicted that it reduced under 6 log (/Z/ohm) after 22 years, so that the protection of the pipe surface from corrosion would be lost. On the other hands, the EIS of outer coal-tar enamel coatings was predicted after about 28 years. Second, the epoxy resin lining is expected to have a slightly longer service life compared to inner coal-tar enamel lining, although the years of aging are close to 20 years. The EIS was predicted to be reached at 6 log (/Z/ohm) after at least 60 years. However the relationship coefficient of prediction function was low as 0.11. Third, the cement mortar lining used in ductile iron casting pipe was predicted to lose the function of CML after 40 years at under 450 mm diameter and at least after 60 years over 500 mm diameter.
The effects of hydrodynamic cavitation solubilization on methane production from waste sludge in anaerobic digestion reactor were researched by the BMP (biochemical methane potential) test and full scale test. As the results of BMP test, the cumulate methane yields before and after solubilization increased from 0.55 to 0.62 L-CH4/g-COD, respectively. The kinetic constant before and after solubilization were 0.0713 and 0.0987 d<sup>-1</sup>, respectively. As the results of full scale test, SCOD concentration of waste sludge before solubilization was 133~409 mg/L and after solubilization was 302~1,280 mg/L. Biogas production was increased from 6,500 m<sup>3</sup>/d to 7,100 m3/d by solubilization. At this point, methane yield after solubilization was higher about 1.1 times than before solubilization. As the hydrodynamic cavitation cycle was increased, the solubilization rate of waste sludge was enhanced and methane production in anaerobic digestion reactor was increased.
The isotherm sorption and sequential desorption of ibuprofen were investigated using wetland sediment with several conditions such as pH 3, 3% of salinity, and 1 M Na-citrate as a dissolved organic matter (DOM), and salinity on sorption and desorption of ibuprofen in water/sediment system. Two sorption models such as linear and Freundlich models and two desorption resistance models such as bi-phasic desorption model and its modified model were used to fit the experimental data. The linear and Freundlich models fitted well to the sorption data (R<sup>2</sup>>0.99) and the bi-phasic desorption model (BPDM) and the modified bi-phasic desorption model (MBPDM) also fitted well to the desorption data (R2>0.98). For sorption, KF in Freundlich model was estimated in order of 9.1 (3% salinity) > 7.4 (pH 3) > 4.8 (Na-citrate) in accordance to Kp in linear model. For desorption, both BPDM and MBPDM fitted well the sequential desorption experiments. The final desorption resistance were also positively affected by salinity but negatively influenced by the presence of Na-citrate as DOM.
A lake water being used as drinking water source has been focused on the quality despite the limitation of the quantity. In particular, degradation of water quality can result from various pollutants sources including multiple land use activities. Algae blooms seriously threaten water quality and the supply of drinking water. In this study, the performances of membrane filtration (MF) using stirred dead end filtration cell(membrane module: material; PVDF, pore size; 0.22㎛) on pollutants removal with dissolved organic matter(DOC) and algae loading in an eutrophicated lake water was assessed. Batch tests were carried out with artificial water using eutrophicated lake water. Applied membrane permeate flux was 0.5 m<sup>3</sup>/m<sup>2</sup>.d. Influent concentrations were in the range of UV254 <0.24cm<sup>-1</sup>, DOC <9.5 mg/L, chlorophyll a (chl-a) 220㎍/L, dissolved TN(DTN) 0.6mg/L, and DTP 0.02mg/L. As a result, the chl-a concentration showed a maximum value on 20 day and the concentration of DOC have begun increasing from the initial stage of algae growth. For taste and odor removal, MF process achieved relatively low removal of approximate 12% for geosmin and 2-MIB. The permeate flux of MF also decreased with increase of TMP, which was 8 times greater than initial TMP. This result indicates the MF process coupled with a pretreatment processes such as activated carbon adsorption and/or coagulation and oxidation in order to mitigate membrane fouling as well as the production of good quality.
This hydraulic model experiment analyzed plunge pool of downstream and sulfur change of downstream depending on discharge flow in order to produce the optimal design plan of auxiliary spillway to be established. To that end, hydraulic characteristics of existing spillway were examined and hydraulic model experiment was conducted on design 1 and 2. First, the results of design 1 show that discharge ability is fine, approach velocity is within limits, but there is a need for improvement through a baffle wall shape change as a whirlpool occurs because of a baffle wall. In the case of sulfur of downstream water flow discharged from steep spillway is not sufficiently reduced and flows into downstream in super-critical flow condition. And as for PMF, near the spilling basin of the existing spillway and spilling basin of auxiliary spillway, unstable phenomena and whirlpool of water surface partially occur, but when considering that water level change is not significant at measuring points in the cross section of downstream as the main flow direction is concentrating into the center of downstream, the danger regarding downstream is limited as found in the analysis. Lastly, the analysis found that the factors risking original functions and safety of spillway structure occurring in the design 1 do not occur in the design 2, and show stable flow characteristics compared with the design 1. Therefore, detailed data regarding size and form of plunge pool and distribution characteristics of flow going into downstream are secured additionally through experiments, they will serve as very useful basic data for designing auxiliary spillway of similar dams.
Depending on climate change, abnormal floods and typhoons other than in the past are common. The dam shall reduce flood damage in downstream areas by controlling the amount of discharge from flood occurrence. However, the initial conditions of a dam in the simulation operation of a flood dam can be very important to show the results of the dam simulation analysis. In this study, the results of flood operation of dams were analyzed due to changes in the initial water level of the reservoir. The initial level of the five typhoons in the Andong Dam basin was changed from EL.160.0 m, the full water level of Andong Dam, to EL.150.0 m at 0.5 meter intervals. The change in the flood control rate was 36.96% for memi with the greatest peak inflow, or 100% for EL.160.0 m and 100% for EL.152.0 m. The flood retention rate was found to be 55.20% at EL.160.0 m and 22.61% at EL.150.0 m in Ewinia, where the total inflow of water was greatest. In case of discharge rate, in sanba, 99.58% of the flow rate of flooding was discharged from the space of EL. 160.0 m.
It takes very long to measure a crack with the use of a CCTV robot for inspecting sewer defects. That is because it is required to remove many impurities deposited in a pipe in order to put and move a CCTV robot in the sewer pipe. The sewer defect inspection system developed to save such temporal and financial costs is designed to go to the middle part of a sewer pipe and make inspection and measurement with the uses of thermal images and CCTV. For performance test and evaluation, a 600 mm concrete pipe and a 300mm PVC pipe were buried 15m, respectively. As a result, it was possible to clearly find very small cracks, which are hard to be detected with the naked eye in CCTV, through thermal imaging, and to quantitatively analyze a crack area with the crack area calculation program using the developed thermal imaging data. The performance of the sewer defect inspection system developed in this study can be classified into three types as follows. First, by checking cracks through thermal detection and CCTV and using the crack area calculation program developed in this study, it was possible to find a crack area quantitatively. Secondly, through quantitative defect inspection, it was possible to select a proper repair construction method depending on a type of defects, a size, and a position, and thereby to remarkably reduce uncertain factors which can arise under an engineer's judgment only. Finally, there was cost saving in the defect inspection. In other words, by using the pipe wall in the middle part of a sewer pipe, not in its bottom, it was possible to inspect defects regardless of impurities and thereby to considerably save the cost for removing impurities.
The water should be evenly distributed to each flocculation/sedimentation basin because it can affect the floc formation and the efficiency of sedimentation. In order to find the optimum operation method for the equal distribution of the flow rate by using the CFD (Water-CFD), the flow analysis was carried out by considering the basic operation condition and improvement plans. From the results of the CFD simulation, the following conclusions were obtained. When 8 all flocculation/sedimentation basins were operated, the influx of the outermost 1st and 8th flocculation/sedimentation basins were the largest but the amount of 4th and 5th flocculation/sedimentation basins which were located at the center of the distribution channel were the least. The operation rate of water purification plant was 40% compared to facility capacity, therefore it was considered to stop the flocculation/sedimentation basins. The optimum operation method to minimize the influent flow difference was the stopping the 4th and 5th flocculation/sedimentation basins located at the center. The other methods such as the extension of the distribution channel(waterway) and the installation of the disturbance plate near the inlet of flocculation basin need the civil engineering work and the lots of extra costs. However, the effect of the equal distribution is not greater than the change of operation method.
The Han River discharges 18×109 tones of freshwater per year into the Yellow Sea, and its variation of water quality influences its estuary. In order to analyze the direct effect of the long-term variations of the water quality and material flux on the ecosystem of the Han River’s estuary, we collected water quality data(e.g., water temperature, dissolved oxygen, COD, nitrogen, phosphorus, suspended solids(SS), and chlorophyll-α) for 23 years(1994~2017). Discharge from the Han River into the Yellow Sea was influenced by rainfall of the watershed of the river based on positive relation between the discharge and amount of rainfall, but the discharge has been seasonally regulated by dams constructed in up- and mid-stream. Phosphate and ammonia concentrations showed a decline while nitrate concentrations consistently increased. COD and SS displayed a decline before the dam construction in 2013 but increased afterwards. On the contrary, DO consistently increased before dam construction in 2013 but decreased afterwards. Change in water quality by river discharge was distinct when river discharge was minimal.This resulted in distinct seasonal change. The flux of COD, chlorophyll-α, ammonia and phosphate decreased, but SS flux increased after 2013 which means that the flux of organic matter and nutrients decreased when the SS flux increased.