본 연구는 중소규모 고도정수처리시설(Y 정수장)에 적용된 세라믹막 여과공정의 운영 효율을 평가하고, 막오염의 주요 원인을 규명하며 실질적인 개선 방안을 제시하는 것을 목적으로 한다. 최근 세라믹막은 내구성과 내약품성이 우수하여 전오존 및 입상활성탄(GAC) 공정과의 조합에 적합한 기술로 주목받고 있으나, 막차압(TMP) 상승 및 장기 안정운영에 어려움이 존재한다. 본 연구에서는 2017년 실제 운영 데이터를 바탕으로, 망간 및 용존유기탄소(DOC)를 중심으로 한 원수 수질과 TMP 변화 간의 상관관계를 분석하였다. 그 결과, 수온역전이 발생하는 봄⋅가을철에 조류와 망간 농도가 증가하면서 TMP가 급상승하는 경향이 확인되었다. 또한 LC-OCD 분석을 통해 조류 유입 시기에는 바이오폴리머 농도가 증가하며 막오염에 직접적인 영향을 미치는 것으로 나타났다. 화학세정 실험에서는 pH 0.7의 황산이 망간, 철, 알루미늄 등의 무기성 침착물 제거에 가장 효과적인 것으로 확인되었으며, 세정 조건의 최적화 필요성이 강조되었다. 아울러 여과 유속의 불균형 및 계열 간 부하 집중이 TMP 상승에 영향을 미치는 주요 요인으로 분석되었고, 이에 따라 유량 제어 및 청정 주기 조정 등의 개선 전략이 제시되었다. 본 연구는 세라믹막 여과공정의 파울링 특성과 제어방안을 실증적으로 규명하였으며, 계절적 수질 변동에 대응하는 정수처리시설의 효율적인 운영 및 설계에 기초자료로 활용될 수 있을 것이다.

본 연구는 조류가 발생하는 낙동강에 위치한 정수장에서 남세균 및 마이크로시스틴(MC)을 분석하였다. 마이크로시스틴 분석을 위한 독소 추출 방법의 효과를 확인하였다. 정수처리 공정별로 취수원수, 착수정수, 전오존 처리수, 응집⋅침전 처리수, 여과 처리수, 정수의 수질을 분석한 결과, 탁도와 클로로필-a 농도는 공정 진행에 따라 크게 감소하며 남세균이 효과적으로 제거되었음을 확인하였다. 마이크로시스틴 분석을 위해 세포 내 독소 추출을 위한 초음파 처리, 동결/해동법, 메탄올 추출법을 비교한 결과, 동결/해동법이 가장 효과적인 것으로 나타났으며, 메탄올 추출법은 상대적으로 낮은 추출 효율을 보였다. 본 연구 수행 시 남세균이 충분히 발생하지 않아 모든 샘플에서 마이크로시스틴이 검출되지 않았다. 따라서 고농도 남세균 발생시 정수장 공정별 남세균 및 독소 농도에 대한 후속 연구가 반드시 필요하다고 생각된다. 정수처리공정은 남세균과 독소를 제거하는 데 있어서 가장 중요한 부분이며 공정에서의 남세균과 독소의 제거 능력을 정확히 분석하는 것이 중요하다.

In treatment processes of drinking water, the use of disinfectants is essential for eliminating microorganisms and pathogenic viruses. Chlorine dioxide (ClO2) is one of the most promising disinfectants. To ensure its effective application in drinking water treatment, it is crucial to investigate the stability and reactivity of ClO2 in drinking water treatment environments. Therefore, we examined the effects of various environmental factors such as temperature, light type, fluorescence intensity, and water quality on its stability. We also examined its reactivity with activated carbon and other inorganic compounds such as coagulants and hypochlorous acid. Findings revealed that ClO2 stability was influenced by several environmental factors. Typically, ClO2 is highly volatile. However, the rate of its volatility is independent of its concentration. As temperature and fluorescent light intensity increased, the concentration of ClO2 showed a rapid decline. Additionally, the presence of activated carbon significantly reduced ClO2 levels. In contrast, the reactivity of ClO2 with coagulants and hypochlorous acid was negligible. These findings provide essential insights for optimizing the use of ClO2 in drinking water treatment facilities.

Chironomid larvae in drinking water treatment plants (DWTPs) and tap water lead to highlights the urgent need for effective control measures. The use of combined disinfectant treatments is becoming increasingly common to achieve optimal disinfection efficiency while minimizing residual contamination. This study was conducted to study the effect of combined treatment of disinfectants used in DWTPs on the biological control potential of chironomid larvae. In the experiment, Glytotendipes tokunagai larvae reared according to OECD guidelines were exposed to NaOCl, UV, and O3 complex substances, and biological responses were analyzed using survival rate and body color change as key indicators for 24 hours. The survival rate of larvae exposed to combined disinfectants mostly decreased in a time- and concentration-dependent manner, and lightening of body color was observed. The most significant decrease (53%) of the survival rate was observed to a combination of UV and 4 ppm NaOCl disinfectants and body color change also showed a statistically significant difference compared to the control group (P<0.001). The change in body color is suggested to be a physiological change caused by oxidation of hemoglobin due to exposure to disinfectant complexes. The results of this study contribute to determining the biological impact of combined disinfectant treatment on chironomid larvae of DWTPs, and can be used as data to suggest the biological control potential of disinfectants. In addition, it will provide important information for setting standards for combined disinfectant treatment to improve water quality in the future.

The number, size, and material distribution of microplastics (MPs) sized 20-200 μm in the raw water and water treatment processes were analyzed using FT-IR in three water treatment plants in Jeju Province. The number of MPs was detected at 0.075-0.620 MP/L in raw water and 0.040-0.047 MP/L in filtered water, which is relatively lower than the results of other studies. Regarding the size of the MPs, particles sized 20-50 μm in both the raw water and the treated water accounted for the highest proportion, representing 65.6% and 56.3% of the total, respectively. In terms of MP type distribution, polypropylene (PP) was identified as the main type at 58.7%. In the water purification process, the MPs removal efficiency was the highest at 93.5% in the sedimentation and rapid filtration process, followed by 58.4% in membrane filtration and 40.0% in slow filtration. Continuous monitoring of the distribution of MPs in raw water and water treatment processes is recommended.

This study develops a model to determine the input rate of the chemical for coagulation and flocculation process (i.e. coagulant) at industrial water treatment plant, based on real-world data. To detect outliers among the collected data, a two-phase algorithm with standardization transformation and Density-Based Spatial Clustering of Applications with Noise (DBSCAN) is applied. In addition, both of the missing data and outliers are revised with linear interpolation. To determine the coagulant rate, various kinds of machine learning models are tested as well as linear regression. Among them, the random forest model with min-max scaled data provides the best performance, whose MSE, MAPE, R2 and CVRMSE are 1.136, 0.111, 0.912, and 18.704, respectively. This study demonstrates the practical applicability of machine learning based chemical input decision model, which can lead to a smart management and response systems for clean and safe water treatment plant.

PURPOSES : Concrete, which is a construction material, is the most widely used compression material; however, unlike steel, it exhibits nonlinear material characteristics. Therefore, to examine the behavior of structures under the nonlinear conditions of concrete materials, one must select an appropriate numerical-analysis technique and a reasonable material model. When performing the nonlinear numerical analysis of a structure using general-purpose structural analysis software, the stress–strain curve or the Mohr–Coulomb failure criterion is typically employed to consider the nonlinear material characteristics. In this study, an efficient nonlinear numerical analysis is conducted by defining the stress–strain curves and Mohr–Coulomb parameters applicable to Strand7 to examine and design the stability of reinforced concrete structures. METHODS : This study was conducted by improving existing data. Based on the tensile region of the concrete stress–strain curve presented in a simple shape and the results of the splitting test, the proposed Mohr–Coulomb parameter was improved based on regulations stipulated in the design standards of concrete structures. The characteristics and usability of the improved material models were examined using concrete splitting tensile and bending models. RESULTS : A yield area distribution similar to that of the reference data is obtained when the Mohr–Coulomb material model is used in the numerical analysis of the concrete splitting tension, thus confirming the validity of the model. In the Mohr–Coulomb material model, nonlinear resistance continues even after the maximum reaction force occurs. However, when the stress–strain curve material model is applied, at the moment the maximum reaction force occurs, the material yields and begins to be damaged. In addition, by applying the Mohr–Coulomb material model to the bending numerical-analysis model, the magnitude of stress in the tensile region from the initial stage exceeds the yield stress defined in the stress–strain curve. CONCLUSIONS : Based on a series of examples, the usability of the proposed concrete stress–strain curve and Mohr–Coulomb parameters is confirmed. However, to obtain numerical-analysis results that are consistent with the nonlinear behavior of actual structures, nonlinear testing of reinforced concrete structures shall be conducted and material models shall be improved.

폐수 처리는 담수 공급의 수요를 맞추고 동시에 환경 오염을 제어하기 위한 가장 중요한 기술 중 하나이다. 여러 종류의 증류법과 역삼투 공정과 같은 다양한 기술은 더 높은 에너지 투입을 필요로 한다. 축전식 탈염(CDI) 기술은 전력 소 비가 매우 적어 슈퍼커패시터 원리에 기반한 대안으로 떠오르고 있다. 공정의 효율성을 향상시키기 위해 전극 재료를 개선하 기 위한 연구가 계속되고 있다. 역전기투석은 가장 일반적으로 사용되는 담수화 기술 및 삼투압 발전기이다. 역전기투석의 효 율을 향상시키기 위해 수행된 많은 연구 중, 맥신(MXene)은 이온교환막 및 2차원 나노유체 채널로서 역전기투석의 물리적 및 전기화학적 특성을 향상시킬 수 있는 유망한 방법으로 떠오르고 있다. 맥신은 단독 사용뿐만 아니라 다른 물질들이 맥신 과 혼합되어 복합막의 성능을 더욱 향상시킨다. 전처리를 거치거나 Ti3C2Tx, 나피온 등을 포함한 이종구조를 가진 맥신은 각 각 최대 담수화 성능 측정 결과를 통해 담수화 산업에서 유망한 재료로 맥신의 잠재력을 입증했다. 역전기투석을 통한 삼투 압 발전 산업에서 이온교환막에서 비대칭 나노유체 이온 채널에 맥신을 사용함으로써 최대 삼투압 출력 밀도를 크게 향상시 켰으며, 대부분 상용화 기준값인 5 Wm-2를 넘었다. 일정 개수의 단위체를 연결함으로써 매개체의 도움 없이 전자기기에 직접 적으로 전력을 공급할 수 있는 수준의 전압이 출력됐다. 본 리뷰에서는 맥신 복합막을 기반으로 한 전기투석 공정의 최근 연 구들에 대해 설명한다.

The emergence of micropollutants in natural water sources due to the overuse of anthropogenic chemicals in industry and households has threatened the production of clean and safe tap water in drinking water treatment plants. Conventional physicochemical processes such as coagulation/flocculation followed by sand filtration are not effective for the control of micropollutants, whereas chemical oxidation processes (applying chlorine, permanganate, ozone, etc.) are known to be promising alternatives. Determining the optimum oxidant dose is important issue related to the production of disinfection by-products as well as unnecessary operating cost, and is made possible by simulations of target-micropollutant abatement based on kinetic model equation consisting of second-order rate constant (between the oxidant and the target) and oxidant exposure. However, the difficulty in determining oxidant exposure as a function of complex water quality parameters limits the field application of kinetic model equation. With respect to representative oxidants used in drinking water treatment plants, this article reviews two main approaches for determining oxidant exposure: i) direct measurement in situ and ii) prediction by empirical models based on key water quality parameters. In addition, we discussed research requirements to improve the predictive accuracy of the empirical models for oxidant exposure and to develop a rational algorithm to determine optimal oxidant dose by considering the priority of the target pollutants to be treated.

To improve the safety of tap water, a study was conducted on the introduction of sanitation safety certification system for water treatment plants(WTPs). In order to produce and supply safe tap, the inflow of pollutants should be blocked as much as possible during the tap water production process, and contaminated materials should be removed or inactivated to a safe level in the WTPs. In order to block the inflow of pollutants in WTPs, it is necessary to strengthen the sanitation management such as installation of facilities for preventing inflow and habitat of larvae, and to remove or inactivate pollutants in the tap water production process, strengthening the safety management such as enhanced turbidity management is needed. Sanitation and safety management in the WTPs can be significantly improved by introducing certification system of WTPs. This will induce continuous improvement in water purification plants with insufficient sanitation and safety management, and provide incentives for WTPs with good sanitation and safety management. In addition, when the WTPs sanitation and safety certification system is established, it is desirable to expand the proposed system from WTPs to the entire process of tap water production and supply.

국내 Y정수처리시설에 20-40 m3/m2/h의 표면부하율을 갖는 고속 용존공기부상공정을 도입하였다. 우선, 용존공기부상공정과 입상활성탄 공정이 결합된 반응기를 일처리용량 500 m3/day의 조건으로 운전하였다. 운전결과는 두 공정이 원수내 탁도, 조류, 지오스민, 2-MIB를 감소시킬 수 있음을 증명하였다. 도출된 최적 설계요소를 활용하여 현장규모의 공정(5,000 m3/day)에 용존공기부상공정을 도입하였다. 여름철 56일간 조류와 탁도 제거율을 평가하였다. 처리수 내 조류의 개체수는 20-30 cells/mL 이하로 유지되었으며, 조류 제거효율은 80-89%를 기록하였다. 침전법 및 용존공기부상공정 처리수질의 탁도 제거효율을 비교한 결과 평균 탁도 제거효율은 77%를 나타냈다. 이러한 결과들은 고속 용존공기부상공정이 여름철 음용수의 탁도 및 조류와 같은 저밀도 고형물을 제거하는데 유의미한 방법임을 나타냈으며, GAC는 맛･냄새를 유발하는 화합물(지오스민, 2-MIB)를 제거할 수 있는 공정 옵션인 것을 확인하였다.

In this study, using the developed pilot device, an experiment was conducted with groundwater according to the calcium carbonate concentration and silica concentration for a certain period of time to determine the degree of RO membrane contamination according to water quality. In addition, using wastewater with severe fouling of raw water, the treatment efficiency is compared through an experiment with a pilot device, the operation progress is evaluated for the scale effect, and the stability and convenience of the developed product are considered.

정수기는 일반적인 산업용 막여과 수처리 공정과 다르게 운전과 휴지를 반복하는 특성이 있다. 이러한 특징 때문 에 역삼투막을 사용하는 정수기의 경우, 재정수시에 정수수의 농도가 정상적인 값보다 높게 나오는 현상(제거율이 정상값보 다 낮게 나오는 현상)이 있는데, 이를 “TDS creep”이라고 한다. 본 연구에서는 휴지시간과 농도에 따른 TDS creep 정도를 관 찰하였다. 또한, TDS creep 현상을 저감하기 위해 원수 세척, 정수부의 부피 증가 및 정수 세척 방법 등을 시험하였고 이에 대한 실질적인 효과를 관찰하였다. 이러한 방법들 중에 정수수의 세척과 같이 역삼투막의 feed side와 permeate side의 농도차 를 최소화하는 것이 TDS creep 현상을 해소하는 궁극적인 해결책임을 확인하였다.

The time series data of rotifer community focusing on the species number and total density were collected from 29 reservoirs located at Jeonnam Province from 2008 to 2016 quarterly. The reservoirs had similar weather condition during the study period, but their sizes and water qualities were different. To analyze the temporal dynamics of rotifer community, the medians, ranges, outliers and coefficient of variation (CV) value of rotifer species number and abundance were compared. For the temporal trend analysis, time series of each reservoir data were compared and clustered using the dynamic time warping function of the R package “dtwclust”. Small-sized reservoirs showed higher variability in rotifer abundance with more frequent outliers than large-sized reservoirs. On the other hand, apparent pattern was not observed for the rotifer species number. For the temporal pattern of rotifer density, COD, phytoplankton abundance fluctuation, and cladoceran abundance fluctuation have been suggested as potential factor affecting the rotifer abundance dynamics.

Water treatment process simulator is the tool for predicting sequential changes of water quality in a train of unit processes. This predicts the changes through governing equations that represent physicochemical performance of each unit processes with an initial and boundary conditions. Since there is no operational data for the design of a water treatment facility, there is no choice but to predict the performance of the facility by assuming initial and boundary conditions in virtual reality. Therefore, a simulator that can be applied in the design stage of a water treatment facility has no choice but to be built as a numerical analysis model of a deductive technique. In this study, we had conducted basic research on governing equations, inter-process data-flow, and simulator algorithms for the development of simulators. Lastly, this study will contribute to design engineering tool development research in the future by establishing the water treatment theory so that it can be programmed in a virtual world and suggesting a method for digital transformation of the water treatment process.