구수환 Soo-hwan Ku , 임지열 Jiyeol Im , 어성욱 Seong-wook Oa , 길경익 Kyungik Gil

DOI:10.15681/KSWE.2017.33.3.247 Vol.33(No.3) 248-256, 2017

This research was conducted to analyze removal efficiencies of non-point pollution source (NPS) in low impact development (LID) facilities with vegetation. In this research, removal efficiencies of NPS were calculated using rainfall monitoring data for 5 years in grassed swale (GS) and vegetative filter strip (VFS). TSS was greater than other pollutants, and it ranged 11.9 ~ 351.7 mg/L in GS and 12.8 ~ 350.7 mg/L in VFS. Outflow EMCs were reduced than inflow EMCs, overall removal efficiencies of NPS were 67 ~ 86% in GS and 63 ~ 91% in VFS. 50 % reduction efficiency of rainfall runoff was observed between inflow and outflow in each LID facility. TSS removal efficiency in GS and VFS was correlated with rainfall characteristics. The rainfall for TSS removal efficiency over 50% was determined about 31 mm, 34 mm and average rainfall intensity was 3.0 mm/hr, 3.9 mm/hr in GS and VFS.. Therefore, GS and VFS were regarded effective LID facilities as removal of pollutants and rainfall runoff. Also, this research result can be used as an important data for management of NPS.

Best management practice (BMP), Grassed swale (GS), Low impact development (LID), Non-point pollution source (NPS), Vegetative filter strip (VFS)

김용탁 Yong-tak Kim , 김진영 Jin-young Kim , 이재철 Jae Chul Lee , 권현한 Hyun-han Kwon

DOI:10.15681/KSWE.2017.33.3.256 Vol.33(No.3) 256-272, 2017

Extreme rainfall has become more frequent over the Korean peninsula in recent years, causing serious damages. In a changing climate, traditional approaches based on historical records of rainfall and on the stationary assumption can be inadequate and lead to overestimate (or underestimate) the design rainfalls. A main objective of this study is to develop a stochastic disaggregation method of seasonal rainfall to hourly extreme rainfall, and offer a way to derive the nonstationary IDF curves. In this study, we propose a novel approach based on a Four-Parameter Beta (4P-beta) distribution to estimate the nonstationary IDF curves conditioned on the observed (or simulated) seasonal rainfall, which becomes the time-varying upper bound of the 4P beta distribution. Moreover, this study employed a Bayesian framework that provides a better way to take into account the uncertainty in the model parameters. The proposed model showed a comparable design rainfall to that of GEV distribution under the stationary assumption. As a nonstationary rainfall frequency model, the proposed model can effectively translate the seasonal variation into the sub-daily extreme rainfall.

Bayesian, Four Parameter Beta, GEV, IDF, Nonstatioanry

엄한기 Han Ki Eom , 김성철 Sung Chul Kim , 김성수 Sung Su Kim , 김삼주 Sam Ju Kim

DOI:10.15681/KSWE.2017.33.3.273 Vol.33(No.3) 273-281, 2017

his study undertook to evaluate the performance of stream purification equipment system, a combination of MBP (Micro Bubble Process) and AGBP (Aerobic Granular Biofilm Process). Based on the results obtained, the optimal HRT (Hydraulic Retention Time) of MBP and AGBP were set as 0.72 and 2.4 h，respectively. Results showed that with continuous operation of combined MBP and AGBP，it is possible to achieve a BOD, TSS and T-P removal efficiency of 85, 90 and 94%, respectively. It further confirmed that the quality of the stream water can be purified by increasing the circulation flow through water simulation evaluation, by applying the QUAL-NIER model. Consequently, this purification system can resolve the current problems of stream purification and dry stream.

AGBP, Dry stream, Equipment type, MBP, Stream purification

박형석 Hyung-seok Park , 정세응 Se-woong Chung , 정선아 Sun-a Choung

DOI:10.15681/KSWE.2017.33.3.282 Vol.33(No.3) 282-290, 2017

Persistent turbidity is defined as the long-term resuspension of small particles. It is one of the most important water qualities of the dam reservoir systems located in North Han River. Persistent turbidity results in aesthetic nuisance and harmful effect on the health of the ecosystem, in addition to elevated costs for water treatment for supplying drinking water supply to the Seoul metropolitan area. These harmful effects have been intensified with increasing strength and frequency of rainfall due to climatic changes in the basin. This study analyzed the effect of an extreme turbidity flow event that occurred in 2006, on the serial reservoir system (Soyang-Uiam-Cheongpyung-Paldang) located on the North Han River. The CE-QUAL-W2 model was set up and calibrated for the river and reservoir system, using the field data obtained in 2006 and 2007. The results showed that for 334 days, turbid water was released by the Soyang Reservoir, which was classified as having TSS concentration greater than 25 mg/L with peak TSS of 264.1 mg/L, after the extreme flood (592.7 mm) that occurred between 10th-18th July, 2006. The turbid water released by the Soyang Reservoir reached the most downstream Paldang Reservoir after about 20 days, and was sustained for 41 days, which was validated with water treatment plant data. Since the released water from Soyang Reservoir had low water temperature and high TSS, an underflow formed in the downstream reservoirs and vertically mixed at Paldang Reservoir due to dilution by sufficient inflow from the South Han River.

CE-QUAL-W2, Extreme event, North Han River, Persistent turbidity, Turbidity flow

안지홍 Ji-hong An , 김중현 Jung-hyun Kim , 박환준 Hwan-joon Park , 김선유 Sun-yu Kim , 박성애 Sung-ae Park

DOI:10.15681/KSWE.2017.33.3.291 Vol.33(No.3) 291-301, 2017

This study was carried out to investigate the distribution of alien plants in the Gyeong-In Ara Waterway. The alien plants were a total of 82 taxa: 17 families, 63 genera, 80 species, and 2 varieties. This number corresponds to 25.5% of the alien plants identified in Korea. The proportion of alien plants in every year increased from upstream to downstream. Given our analysis of vegetation stratification, a riverbank was covered with artificial materials to prevent vegetation from growing; it had a step-type cross section. The flood plain consisted of the waterfront area. The array of vegetation was not a typical dispersion, and terrestrial and alien plants dominated the Gyeong-In Ara Waterway. Evaluation of naturalness based on the vegetation stratification showed grade 3 or 4. In order to solve a problem, the method and level of restoration should be chosen based on diagnostic assessment. Therefore, we need to restore the step-type cross section as pool type one. From waterfront to bank in this waterway, we recommend introducing native plants by imitating reference species composition. Since the invasion by alien plants is expected to be accelerated by the continuous artificial disturbance，we recommend quantitative investigation of the invasion by alien plants and monitoring the change of distribution.

Alien plants, Monitoring, Restoration plan, Vegetation stratification

윤금회 Geumhee Yun , 윤주환 Zuwhan Yun

DOI:10.15681/KSWE.2017.33.3.302 Vol.33(No.3) 302-310, 2017

The morphological characteristics of granules developing in anaerobic-anoxic (An-Ax) and anaerobic-aerobic (An-Ox) sequencing batch reactors (SBRs) were examined. The granules developed in the both SBRs after 200 days of laboratory operation. The average diameters of the granules were 2.2 土 1.7 mm in the An-Ax SBR and 0.4 ± 0.3 mm in the An-Ox SBR. To determine the possible factors affecting morphology of granules a comparative analysis of various operating conditions from reference data indicated that the availability and type of electron acceptors is a key factor determining the granulation process and granular morphology.

Denitrifying phosphorus accumulating organism (dPAO), Electron acceptor, Morphology, Granule, Phosphorus accumulating organism (PAO), Sequencing batch reactor (SBR)

공동수 Dongsoo Kong , 김아름 Ah Reum Kim

DOI:10.15681/KSWE.2017.33.3.311 Vol.33(No.3) 311-325, 2017

A habitat suitability index (HSI) was developed using three physical habitat factors (current velocity, water depth and substrate) based on ecological monitoring of 17 benthic macroinvertebrate taxa in a Korean stream (Gapyeong). The Weibull model was used as a probability density function to analyze the distribution of individual abundance in relationto physical factors. Numbers of species and total individual abundance increased with increasing current velocity and mean diameter of substrate, and decreased with increasing water depth. Most taxa showed a clear preference for a fast current velocity, shallow water depth and coarse substrate, except Ephemem，Potamanthidae (mayfly), and Plectrocnemia (caddisfly), which were rheophobic, potamophilic and lithophobious. Based on the canonical correspondence analysis, the relative importance of each factor was determined as follows: current velocity > substrate > water depth.

Benthic macroin vertebrates, Environmental flow, Gapyeong stream, Habitat Suitability Index

유지수 Jisu Yoo , 정세웅 Se-woong Chung , 박형석 Hyung-seok Park

DOI:10.15681/KSWE.2017.33.3.326 Vol.33(No.3) 326-333, 2017

Lakes and reservoirs have been reported as significant sources of carbon emissions released into the atmosphere of many countries. Although field experiments and theoretical investigations based on the fundamental gas exchange theory have proposed quantitative amounts of Net Atmospheric Flux (NAF) in various climate regions, there is significant uncertainty about the global scale estimation. Mechanistic models can be manipulated for understanding and estimating temporal and spatial variations of NAFs for considering complex hydrodynamic and biogeochemical processes in a reservoir, but such models require extensive and costly datasets and model parameters. However, data driven machine learning (ML) algorithms are likely to be alternative tools to estimate NAFs in responding to independent environmental variables. The objective of this study was to develop random forest (RF) and multi-layer artificial neural network (ANN) models for the estimation of the daily CO₂ NAFs in Daecheong Reservoir located in Geum River in South Korea, and compare the models` performance against the multiple linear regression (MLR) model that was proposed in the previous study (Chung et al” 2016). As a result, the RF and ANN models revealed much enhanced performance in the estimation of high NAF values, while the MLR model significantly underestimated them. A cross-validation with 10-fold random samplings was applied to evaluate the performance of the three models，and it indicated that the ANN model is best, followed by RF and MLR models.

Artificial neural network, Carbon emission, Daecheong Reservoir，Machine learning, Random forest

최수영 Su Young Choi , 권민욱 Min Wook Kwon , 박기영 Ki Young Park , 차호영 Ho Young Cha , 김희준 Hee Jun Kim , 권지향 Ji Hyang Kweon

DOI:10.15681/KSWE.2017.33.3.334 Vol.33(No.3) 334-340, 2017

A pilot-scale electrodialysis system was designed and constructed to treat groundwater polluted with arsenic and manganese. Synthetic groundwater, in which some amount of arsenic (As) and manganese (Mn) were added to a final concentration of 500 mg/L of Mn and 50 pg/L of As, was used as a feed for the ED system. The limiting current density, linear water velocity, applied voltage, and membrane surface area were investigated to obtain the efficient and economic operation of the ED system. The linear water velocity increased from 0.74 cm/s to 1 lcm/s, based on the evaluation of limiting current density. Using the ED system with 14 pairs of ion exchange membranes, the water quality of the diluate after 85 minutes of operation satisfied the water quality criteria for drinking water. Increasing the membrane pairs to 21 and 42 pairs was effective in reducing the conductivities of the diluate. The operation cost of the ED system was assessed using specific energy consumption, which was 1.065~ 1.2 kWli/m3. Considering low salt concentrations of the groundwater, increases in current utilization and low voltage applications are required when the ED system is used to produce drinking water.

Arsenic, Electrodialysis，Groundwater, Ion exchange membrane，Manganese

허인량 In-ryang Huh , 이건호 Geon-ho Yi , 정원구 Won-gu Jeong , 권재혁 Jae-hyouk Kwon

DOI:10.15681/KSWE.2017.33.3.341 Vol.33(No.3) 341-347, 2017

From 2014 to 2016, water quality of Youngrang Lake was surveyed, according to the location and depth. Following observations were recorded. Distribution of dissolved oxygen in the water depth was investigated at the middle section and the downstream 1st, 3rd, 5th, when investigating the bottom lm interval anoxic layer. The organic matter and nutrient concentration distribution was COD upstream 2.8 mg/L, middle section 4.2 mg/L downstream 4.1 mg/L, which was more than two times higher in the bottom layer. The TP concentrations showed a similar trend as the COD, being 0.047 mg/L at upstream, 0.051 mg/L in the middle, and 0.059 mg/L downstream. Difference in salinity was observed at every survey period; the lowest salinity recorded 28.5% during the second survey, and highest was 32.1% in the fourth survey. Korean trophic state index (TSIko) showed eutrophic conditions in the middle section and downstream, whereas mesotrophic state was maintained elsewhere during the entire period. In order to evaluate the cause of water pollution of the Youngrang lake, regression analysis determined the relationship between salinity and DO, COD, TN，TP, Chl-a; the results indicated R2 from 0.63 to 0.95. Youngrang lake water quality had a close relationship with salinity due to inflow of seawater. As a result，in order to improve the quality of Youngrang lake, efficient incorporation of the amount of water through the seawater influent is considered the key.

Eutrophication, Salinity, TSIko, Youngrang Lake

박재홍 Jae Hong Park

DOI:10.15681/KSWE.2017.33.3.348 Vol.33(No.3) 348-358, 2017

The process of evaluating and selecting the best available techniques confers various characteristics for each country. In the case of EU, the BAT is selected through a TWG meeting after the first screening, mass and energy balance, impact assessment, and decision support process. Korea has proposed four principles for the selection of BAT that can be carbon neutral for each environmental infrastructure，in order to reduce greenhouse gas emissions. To evaluate and select the best available technique, it is necessary to differentiate the methods based on its general application at the current workplace, whether it is a single technique or a combination technique, and whether it is a technological or management technique. In the case of single technique, flirther evaluation is required whether it is applied at the workplace, excessive cost，superior environmental performance over BAT, and secondary environmental pollution. In the case of multiple techniques, it is necessary to examine whether the emission standards are met and whether the pollutants can be treated at the same level as BAT. In the case of BAT candidates for management techniques, evaluating their direct/indirect contribution in lowering the emission level of pollutants can be an important factor. In the case of environmental techniques that are not generally applied at the workplace, it is recommended that the following 8 steps be carried out, including those prescribed by law. The first stage lists the performance evaluation factors. In the second stage, the level of disposal of pollutants and the level of satisfaction with standards are listed. The third stage lists the environmental evaluation elements, and the fourth stage lists the economic evaluation elements. Step 6 lists the pollution and accident prevention evaluation factors, step 7 quantitatively evaluates the technical working group, and step 8 is the BAT confirmation through deliberation of the central environmental policy committee.

BAT, Evaluation & Selection, Management technique, Technology technique

김민희 Minhee Kim , 현승훈 Seunghun Hyun , 이원석 Won-seok Lee , Loretta Y. Li

DOI:10.15681/KSWE.2017.33.3.359 Vol.33(No.3) 359-369, 2017

Water distribution systems supply drinking-water to consumers` taps. Internal corrosion of metallic pipe used in drinking-water distribution systems has reduced water quality by increasing its levels of toxic heavy metals, such as lead, copper, and nickel. These problems have been experienced to varying degrees by water utilities in many countries. North America has successfully controlled pipe corrosion and polluted water in water distribution systems by means of various policies, regulations, and rules. Practical and engineering guidelines for evaluating pipe corrosion and deciding on treatment options are also provided to improve drinking-water supplies. In addition, research on the corrosion mechanism in water distribution systems, such as the complex effects of physical and chemical parameters on the corrosion of pipes, has been used to more accurately predict the corrosion rates of metallic pipes in actual water distribution systems. This paper reviews various regulations, policy statement, and treatment procedures concerned with controlling corrosion in drinking-water distribution systems in the US and Canada and offers suggestions for management of polluted water and pipe corrosion in drinking-water distribution system in Korea.

Corrosion index, Corrosive water management, Drinking water quality, Heavy metals, Pipe corrosion