김창규 Chang Gyu Kim , 김요용 Yo Yong Kim , 박익범 Ik Beom Park , 송진호 Jin Ho Song , 남우경 Woo Kyong Nam , 한송희 Song Hee Han , 김복준 Bok Jun Kim , 오조교 Jo Gyo Oh

DOI:10.15681/KSWE.2015.31.2.87 Vol.31(No.2) 87-93, 2015

In this study, the inhibitory effect of toxic metals was investigated on the activated sludge of the municipal sewage treatment plant. The allowable concentration of toxic metals was also estimated for the stable operation of the biological treatment process. The single and mixture toxicity of Cu2+, Al3+ and Zn2+ were evaluated for the activated sludge microorganisms. As a result, nitrifying microorganisms were more susceptible than heterotrophic microorganisms. IC10 (Inhibition Concentration of 10%) of Cu2+, Al3+ and Zn2+ for the nitrifying microorganisms was 3 mg/L, 7 mg/L and 25 mg/L, respectively. The mixture toxicity showed three times more sensitive than the single toxicity. The concentrations of Cu2+, Al3+ and Zn2+ to minimize the inhibitory effect on organic matter removal and nitrification in batch experiments were found to be 1.3 mg/L, 2.5 mg/L and 6.3 mg/L.

activated sludge, Al, Cu, IC10, inhibitory effect, Zn

정권 Jeong Kwon , 김도군 Do Gun Kim , 김석구 Seog Ku Kim , 김원재 Weon Jae Kim , 고석오 Seok Oh Ko

DOI:10.15681/KSWE.2015.31.2.94 Vol.31(No.2) 94-102, 2015

Electro-coagulation experiments were conducted with aluminum (Al) or iron (Fe) electrode in order to determine the optimal electrode material and operation conditions for algae removal. Al electrode showed higher removal rate of algae than Fe electrode because Al flocs have positive surface charges which electrostatically attract algae species having negative surface charges. Removal rate of algae and total phosphorous (T-P) was increased as current density and electrode area increases. It was also found that initial pH with neutral range was optimum for T-P removal by electro-coagulation. Bench-scale continuous flow experiments consisted of electro-coagulation reactor, agitation tank and settling tank were conducted. In electro-coagulation reactor, a large fraction of Al flocs were distributed to scum layer, due to the gas bubbles generated by electrolysis reaction. In agitation tank, most of Al flocs were settled and the optimal mixing intensity was found to be 50 rpm to achieve good settleability. The removal rate of algae was about 90-95%. Additionally, the removal rate of the T-P and COD was observed to be 73.8±8.0% and 75.0±3.8%, respectively. Meanwhile, the removal rate of total nitrogen (T-N) was relatively low at only 24%.

Algae, Electro-coagulation, Nitrogen, Organic Matter, Phosphorus

박현건 Hyun Geoun Park , 박지연 Ji Yeon Park

DOI:10.15681/KSWE.2015.31.2.103 Vol.31(No.2) 103-109, 2015

The characteristics of drinking groundwater at west Gyeong-nam were analyzed by investigating 3,698 cases which were carried out from January 2008 to september 2013. 24.5% of the observed data exceeded the drinking water quality standards. Among the drinking water quality standards, 40 parameters were found to exceed. and most problematic were total coliform and HPC(Heterotrophic Plate Count). The unfit ratio of each region for drinking water were 23.1% at Geoje, 18.7% at Geochang, 28.5% at Goseong, 24.1% at Namhae, 32.8% at Sacheon, 20.5% at Sancheong, 36.9% at Uiryeong, 29.2% at Jinju, 40.9% at Tongyeong, 24.7% at Hadong, 20.6.% at Hamyang, 20.1% at Hapcheon. The result of correlation showed that rainfall and unfit ratio of HPC may be associated with the hydrologic durability and season. The coefficient of correlation between them was 0.304. During the summer, the coefficient of correlation was 0.699. But the significant correlation between total coliform and rainfall was not found.

Coefficient of correlation, Drinking groundwater, Drinking water quality standards excess items, Unfit ratios of each region

유재정 Jae Jeong Yu , 이경락 Keung Lak Lee , 이혜진 Hye Jin Lee , 황정화 Jeong Wha Hwang , 류희성 Heuy Seong Lyu , 신라영 La Young Shin , 박아름 A Reum Park , 천세억 Se Uk Chen

DOI:10.15681/KSWE.2015.31.2.110 Vol.31(No.2) 110-119, 2015

The construction of the eight large weirs in the Nakdong River, the second largest river in Korea, caused big changes in the physical environment of the water system. Algal communities and their correlations with environmental factors, mainly nutrients were studied at five weir areas in the Nakdong River from 2010 to 2013. Water quality, hydrodynamics and algal composition were investigated. Results showed that flow velocities were reduced compared with that before weir construction near the areas where are located in the mid and upstreams of the Nakdong River. A seasonal algal community succession was observed and it was mainly correlated with temperature and phosphorus. Diatoms were dominated from winter to spring months and massive diatomic blooms of Stephanodiscus sp. occurred early in March during survey period. Cyanobacterial blooms of Microcystis sp. occurred from July to September 2013 and was preceded by the lower total phosphorus concentration of 0.05 mg L-1. The correlations between total phosphorus concentrations and algal abundances were not significant during the survey periods. However, significant correlation with cyanobacteria was found in the period of weir construction after only at the GG survey site and blooms periods of 7 times in the survey sites, and its correlation coefficients were 0.53 (p<0.001) and 0.42 (p<0.01) respectively. When algal bloom was observed, partially low nutrient concentration was observed in the Nakdong River. In conclusion, partially low nutrient concentration which may result from algal bloom was observed, and we presume it caused the reduction of algal abundunces.

Algae community, Algal bloom, Environment factor, Nakdong River, Nutrient, Water environment

오성광 Seong Kwang Oh , 김계현 Kye Hyun Kim , 이철용 Chol Young Lee , 유광현 Kwang Hyun Ryu

DOI:10.15681/KSWE.2015.31.2.120 Vol.31(No.2) 120-133, 2015

Due to increasing impervious surfaces resulting from urbanization and industrialization which are directly linked to urban inundation and non-point pollutants runoff, there is a need to manage them systematically. A management over urban impervious surfaces calls for pervious/impervious maps, which enable viewing the distribution of impervious surfaces. Nevertheless, relevant data are absent as now. In this respect, despite the diversity of proposed methods, pilot implementation and accuracy verification have never been conducted. Therefore, this study is aimed to produce a pilot pervious/impervious map based on previously proposed methods and to elucidate its pros and cons with a view to proposing a method for producing a GIS-based optimal pervious/impervious map. Following previously proposed methods, a pervious/impervious map of Bupyeong-gu, Incheon was produced. Then, a method of producing optimal pervious/impervious maps applicable to urban areas was proposed through the comparison of pros and cons of relevant spatial data. As a result, the map had been confirmed 99.2% of classification accuracy. Based on the present findings, future studies should establish a standardized method for producing. Also, this method should be used to produce pervious/impervious maps of other regions so that it can be applied to managing impervious surfaces in major urban areas nationwide.

Geographic Information System, GIS, Impervious Surface, Land Cover, Map Production

최희정 Hee Jeong Choi

DOI:10.15681/KSWE.2015.31.2.134 Vol.31(No.2) 134-141, 2015

The focus of this study was to observe the growth of Chlorella vulgaris and Botryococcus braunii under mixotrophic conditions (i.e., added acorn) with the aim of increasing biomass and triacylglycerols (TAGs) content. The result of investigation indicated that the acorn contains a lot of carbonate (87.29%) and glucose (97.99 mg%). A significant growth of biomass was obtained when grown in acorn rich environment comparing to autotrophic conditions. 3 g/L acorn yielded the highest biomass concentration for these strains. Thus, the biomass productivity with 3 g/L acorn was obtained 2.31 times and 2.10 times higher than that of authotrophic conditions for Chlorella vulgaris and Botryococcus braunii, respectively. The maximum amount of TAGs was reached 14.35% and 18.41% for Chlorella vulgaris and Botryococcus braunii, respectively, in the growth medium with 5 g/L acorn. The effect of acorn could enhance the investigated microalgae growth, biomass productivity and TAGs content. This provides a feasible way to reduce the cost of bioenergy production from microalgae.

Acorn, Biomass, Microalgae, Optical Panel Photobioreactor, Triacylglycerols

공동수 Dong Soo Kong , 김아름 Ah Reum Kim

DOI:10.15681/KSWE.2015.31.2.142 Vol.31(No.2) 142-150, 2015

The relationship between the number of benthic macroinvertebrate species and the accumulated survey area were investigated in a clean stream and an impaired stream of Korea. Five models to characterize species-area functions were compared, and the Weibull model fitted species-area data well. The other models (Arrhenius, Romell-Gleason, Kylin, Lognormal model) had small or notable bias. The maximum number of species and half-saturation area derived from the Weibull model may be used as the indicators of the carrying capacity and the habitat complexity respectively.

Benthic macroinvertebrates, Sample size, Species-area relationship, Weibull distribution

이기희 Ki Hee Lee , 류희구 Hee Gu You , 주현종 Hyun Jong Joo

DOI:10.15681/KSWE.2015.31.2.151 Vol.31(No.2) 151-158, 2015

The aim of this research is to derive an optimum operating condition for the thermal solubilization equipment that is employed to increase concentration of soluble organic materials and to assess whether it would be possible to use the waste sludge generated by thermal solubilization reaction as an external carbon source in biological denitrification process. For the purpose, we have constituted a laboratory-size thermal solubilization equipment and have assessed thermal hydrolysis efficiency based on various reaction temperature and reaction time. We have also derived SDNR using the waste sludge generated by thermal solubilization reaction through a batch experiment. As a result of research, the highest thermal hydrolysis efficiency of about 42.8% was achieved at 190°C of reaction temperature and at 90 minutes of reaction time. And when SDNR was derived using the waste sludge, the value obtained was 0.080~0.094 g NO3--N/g MLVSSㆍday, showing SDNR that is higher than that obtained by the results of existing researches that used common wastewater as an external carbon source. Accordingly, in view of the fact that food wastes vary quite a bit in characteristics based on the area they are generated from and seasonal change, it seems that a flexible operation of thermal solubilization equipment is required through on-going monitoring of food wastes that are imported to food wastes recycling facilities.

Food waste, SDNR, Solubilization, Thermal hydrolysis

김종민 Jong Min Kim , 김보경 Bo Kyong Kim , 김민섭 Min Seob Kim , 신기식 Ki Sik Shin

DOI:10.15681/KSWE.2015.31.2.159 Vol.31(No.2) 159-165, 2015

The organic matter sources of phytoplankton and related environmental factors influencing algal bloom in Paldang reservoir were studied using nitrogen and carbon isotope ratio(δ15N, δ13C). Phytoplankton samples for stable isotope analysis were collected from four points in reservoir using a plankton net. Physicochemical water quality, algal taxa and hydrological data were collected from published monitoring material. Phytoplankton samples were analyzed by IRMS. CN ratio of each sample was very similar to that of phytoplankton from literature cited. δ15N of each sample was decreased during July. Mixing and dilution of nitrogen sources due to increment of influx by concentrated rainfall were considered as the main reason for the decline of δ15N. Based on analyzed δ15N value of each sample, nitrogen source of Bughan river sample was presumed to come from soil. The nitrogen sources of Namhan river and Kyeongan stream samples seemed to be sewage or animal waste. Low δ15N value in August (2012) seemed to be influenced by isotope fractionation due to the blooming of nitrogen-fixation blue-green algae (Anabaena spp.). Variation in δ15N values particularly by blue-green algal bloom was considered the important factor for estimating the organic matter sources of phytoplankton.

CN ratio, δ15N, δ13C, organic matter sources, phytoplankton

최윤호 Youn Ho Choi , 류지철 Ji Chul Ryu , 황하선 Ha Sun Hwang , 금동혁 Dong Huyk Kum , 박윤식 Youn Shik Park , 정영훈 Young Hun Jung , 최중대 Joong Dae Choi , 임경재 Kyoung Jae Lim

DOI:10.15681/KSWE.2015.31.2.166 Vol.31(No.2) 166-180, 2015

Pollutant in watersheds comes from two major sources which are NPS (nonpoint source pollution) and PS (point source pollution). Most of the pollutant can be treated by wastewater treatment plants. However, wastewater treatment plants may not be an appropriate practice to improve water quality for the watersheds with large portion of NPS pollutant and NPS pollution from direct runoff and baseflow has different characteristics. Therefore the practices to improve water quality need to be comprehensive for pollutants by both direct runoff and baseflow. Riparian buffer, one of practices to manage pollutant in watershed, has been applied to reduce pollutant not only from direct runoff but also baseflow. In this study, the scenarios for pollutant reduction by wastewater treat plants and the nitrogen reduction by riparian buffer were simulated using SWAT-REMM to suggest an effective plan for pollutant reduction from baseflow. Riparian buffer provided nitrogen reduction of 0.2~75.0% in YbB watershed and 38.0~47.0% in GbA watershed. The result indicates that riparian buffer is effective to reduce the pollutant especially from baseflow, and it suggested as suitable for the a watershed which WWTP discharge is not capable to reduce enough pollutant.

Baseflow, Non-Point Source, Pollutnat Load, Riparian Buffer, SWAT-REMM

최정규 Jung Kyu Choi , 민중혁 Joong Hyuk Min , 김덕우 Deok Woo Kim

DOI:10.15681/KSWE.2015.31.2.181 Vol.31(No.2) 181-195, 2015

Algal blooms in lakes are one of major environmental issues in Korea. A three-dimensional, hydrodynamic and water quality model was developed and tested in Lake Euiam to assess the performance and limitations of numerical modeling with multiple algal groups using field data commonly collected for algal management. In this study, EFDC was adopted as the basic model framework. Simulated vertical profiles of water temperature, dissolved oxygen and nutrients monitored at five water quality monitoring stations from March to October 2013, which are closely related to algal dynamics simulation, showed good agreement with those of observed data. The overall spatio-temporal variations of three algal groups were reasonably simulated against the chlorophyll-a levels of those estimated from the limited monitoring data (chlorophyll-a level and cell numbers of algal species) with the RMSEs ranging from 2.6 to 17.5 mg/m3. Also, note that PO4-P level in the water column was a key limiting factor controlling the growth of three algal groups during most of simulation period. However, the algal modeling results were not fully attainable to the levels of observation during short periods of time showing abrupt increase in algae throughout the lake. In particular, the green algae/cyanobacteria and diatom simulations were underestimated in late June to early July and early October, respectively. The results shows that better understanding of internal algal processes, neglected in most algal modeling studies, is necessary to predict the sudden algal blooms more accurately because the concentrations of external PO4-P and specific algal groups originated from the tributaries (mainly, dam water releases) during the periods were too low to fully capture the sharp rise of internal algal levels. In this respect, this study suggests that future modeling efforts should be focused on the quantification of internal cycling processes including vertical movement of algal species with respect to changes in environmental conditions to enhance the modeling performance on complex algal dynamics.

Algal dynamics modeling, EFDC, Internal cycling, Lake Euiam, Monitoring

박준대 Jun Dae Park , 오승영 Seung Young Oh , 최윤호 Yun Ho Choi , 김용석 Yong Seok Kim

DOI:10.15681/KSWE.2015.31.2.196 Vol.31(No.2) 196-208, 2015

This study analyzed the characteristics of sewer flow and its water quality, and investigated changes in the characteristics in three areas where the sewer rehabilitation projects have been carried out. In S1 area, the patterns of the flow became regular and the range of the fluctuation decreased after the sewer rehabilitation. The flow and its BOD concentration increased. The infiltration/inflow and exfiltration showed clear distinction before and after the sewer rehabilitation in this area. In S2 area, the patterns and the range of the fluctuation of the flow made no differences before and after the sewer rehabilitation. The flow decreased slightly and its BOD concentration increased considerably after the sewer rehabilitation. Big decrement in stormwater inflow but small in exfiltration appeared in this area. In S3 area, the patterns and the range of the fluctuation of the flow made no differences before and after the sewer rehabilitation. The flow decreased slightly and its BOD concentration increased in a small rate in this area.

Exfiltration, Infiltration/Inflow, Sewer flow, Sewer rehabilitation

류희구 Hee Gu You , 이기희 Ki Hee Lee , 주현종 Hyun Jong Joo

DOI:10.15681/KSWE.2015.31.2.209 Vol.31(No.2) 209-215, 2015

The purpose of this study is to evaluate the characteristic of the iron oxide carrier for removing arsenic contained in the groundwater. 4 types of iron oxide carrier used in the study is iron oxide coated sand carrier (IOCSC), iron oxide coated zeolite carrier (IOCZC), iron oxide plasticity carrier (IOPC) and platinum iron oxide plasticity carrier (PIOPC). The results of this study, IOPC is showed high arsenic adsorption strength and the maximum amount of adsorption than the IOCC. Based on the results of the arsenic adsorption characteristic, by using IOCC was conducted to column test. As a result, PIOPC is showed a high arsenic adsorption amount than IOPC, it was found that the time required to reach the breakthrough point is also extended. Therefore it is determined that stably compliance with water quality standards enhanced drinking water when using the PIOPC.

Arsenic, carrier, groundwater, iron oxidized