최희정 Hee Jeong Choi

DOI:10.15681/KSWE.2014.30.5.469 Vol.30(No.5) 469-476, 2014

The focus of this study was to observe the growth of Chlorella sp., Nannochloris sp., and Botryococcus braunii under mixotrophic conditions (i.e., added glycerol) with the aim of increasing the growth of biomass and algae oil content. A significant growth of biomass was obtained when grown in glycerol rich environment comparing to autotrophic conditions. 5 g/L glycerol yielded the highest biomass concentration for these strains. Mixotrophic conditions improved both the growth of the microalgae and the accumulation of triacylglycerols (TAGs). The maximum amount of TAG in Botryococcus braunii was reached in the growth medium with 10 g/L glycerol and Chlorella sp., Nannochloris sp. with 2 g/L glycerol. The content of saturated fatty acids of Chlorella sp., Nannochloris sp., and Botryococcus braunii was found to be 34.94, 14.23 and 13.39%, and the amount of unsaturated fatty acids was 65.06, 85.78 and 86.61% of total fatty acids, respectively. The fatty acid profiles of the oil for the culture possibility met the necessary requirements and are, therefore, promising resource for biofuel production.

Biomass, Biooil, Glycerol, Microalgae, Optical Panel Photobioreactor

안상도 Sang Do An

DOI:10.15681/KSWE.2014.30.5.477 Vol.30(No.5) 477-485, 2014

Imha Reservoir is connected to Andong Reservoir via a diversion tunnel allowing water to pass between. The diversion tunnel is equipped with screens to exclude exotic largemouth bass due to their predatory impacts on prey assemblages resulting in a degradation of species richness of local fish fauna and extinction of local fish populations in Korea. Flow pattern changes resulting from the fish screens and trash racks were investigated using a computational fluid dynamics (CFD) model. Numerical simulations showed that the decrease in the discharge capacity of the tunnel is approximately 8.6% and the headloss coefficient for fish screen at Andong intake tower was determined to be 1.5. In order not to allow the small fishes enough to pass through the wire openings enter into Imha Reservoir through tunnel, the velocity in the tunnel should be greater than 1.48 m/s which is a critical ascending velocity of the bass. This study suggests that it can keep the velocity higher enough to exclude largemouth bass when a gate opens with the condition of 1.0m difference in water stage between two reservoirs.

Andong-Imha diversion tunnel, Computational Fluid Dynamics, CFD), Fish screen, Flow-3D, Largemouth bass

신소연 So Yeun Shin , 구본흥 Bon Heung Koo , 김태현 Tae Hyun Kim , 이유학 Yu Hak Lee , 안종화 Johng Hwa Ahn

DOI:10.15681/KSWE.2014.30.5.486 Vol.30(No.5) 486-490, 2014

Industrial use of microwave heating as an alternative to conventional heating is becoming popular mainly due to dramatic reductions in reaction time. Therefore, this work experimentally determined the effect of microwave irradiation on ammonia nitrogen removal in wastewater. The effects of air flow rate (0.3~0.9 L/min), treatment temperature (70~100°C), and initial pH (9~11) were characterized. As the air flow rate increased from 0.3 to 0.9 L/min, the ammonia removal rate constant (k) increased from -0.6642 to -1.0755 min-1. As the temperature increased from 70 to 100°C, k increased -0.0338 to -1.0755 min-1. As the pH increased from 9 to 11, k increased -0.2443 to -1.0755 min-1. Ammonia removal was strongly dependent on temperature and pH rather than air flow rate. The results show that microwave irradiation is effective in ammonia nitrogen removal in wastewater due to advantages of fast and effective processing.

Air flow rate, Ammonia nitrogen, Microwave, pH, Temperature

윤성완 Sung Wan Yoon , 박관영 Gwan Yeong Park , 정세웅 Se Woong Chung , 강부식 Boo Sik Kang

DOI:10.15681/KSWE.2014.30.5.491 Vol.30(No.5) 491-502, 2014

As meteorology is the driving force for lake thermodynamics and mixing processes, the effects of climate change on the physical limnology and associated ecosystem are emerging issues. The potential impacts of climate change on the physical features of a reservoir include the heat budget and thermodynamic balance across the air-water interface, formation and stability of the thermal stratification, and the timing of turn over. In addition, the changed physical processes may result in alteration of materials and energy flow because the biogeochemical processes of a stratified waterbody is strongly associated with the thermal stability. In this study, a novel modeling framework that consists of an artificial neural network (ANN), a watershed model (SWAT), a reservoir operation model(HEC-ResSim) and a hydrodynamic and water quality model (CE-QUAL-W2) is developed for projecting the effects of climate change on the reservoir water temperature and thermal stability. The results showed that increasing air temperature will cause higher epilimnion temperatures, earlier and more persistent thermal stratification, and increased thermal stability in the future. The Schmidt stability index used to evaluate the stratification strength showed tendency to increase, implying that the climate change may have considerable impacts on the water quality and ecosystem through changing the vertical mixing characteristics of the reservoir.

ANN, CE-QUAL-W2, Climate change, Juam Reservoir, Reservoir stratification, SWAT

박지형 Ji Hyoung Park , 손수민 Su Min Sohn , 김용석 Yong Seok Kim

DOI:10.15681/KSWE.2014.30.5.503 Vol.30(No.5) 503-511, 2014

The temporal and spatial analyses of total nitrogen (TN) fractionation were conducted in order to understand 1) total nitrogen components in streams and 2) their patterns in rainy and dry seasons. The result showed that the concentration of nitrogen components in stream water was lower in non-urban area and getting higher in urban area. Dissolved total nitrogen (DTN) was 95~97.7% of total nitrogen in streams, and the proportion of dissolved organic nitrogen (DON) and ammonia nitrogen (NH3-N) was higher with increasing urban area. The concentration of total nitrogen and nitrate nitrogen (NO3-N) were highest in winter among four seasons. The result was showed that concentration of NH3-N was same variation as concentrations of TN and NO3-N in urban-rural complex and urban areas, except rural areas. During rainy season, concentrations of particulate organic nitrogen (PON) and NH3-N increased in rural areas and decreased in both urban-rural complex and urban areas. Correlation between total nitrogen components and land uses was positively correlated with site > paddy, and negatively correlated with forest. The variation of total nitrogen concentration was determined by NO3-N in non-urban areas, by NO3-N and NH3-N in urban-rural complex and by NH3-N in the urban areas.

Ammonia nitrogen, Dissolved organic nitrogen, Land uses, Nitrate nitrogen, Particulate organic nitrogen, Total nitrogen components

이윤희 Yun Hee Lee , 어성욱 Seong Wook Oa , 김용석 Yong Seok Kim , 박지형 Ji Hyung Park

DOI:10.15681/KSWE.2014.30.5.512 Vol.30(No.5) 512-516, 2014

Two different methods for TOC (Total Organic Carbon) analysis of livestock manure including high strength solid organics were evaluated. Firstly, an analyzing method by dilution after pre-treated by Ultrasonicator and 100 mesh sieve for homogenization was defined as TOC 1; and secondly method divided by particulate organic carbon (POC) and dissolved organic carbon (DOC) was defined as TOC 2. 116 samples collected from 56 farms were analyzed in TOC1, TOC2, BOD and VSS. TOC1 method showed higher accuracy at less than 30,000 mg/L of TOC while TOC2 method presented significant reliability at over that concentration. Regarding to the sample with the same VSS concentration, the correlation between TOC 2 and VSS (ρ: 0.806) was slightly higher than that between TOC 1 and VSS (ρ: 0.784), resulted from a relatively low loss of solids and a low error probability (dilution and homogenization effects) in the analyzing procedures. In addition, the reliability between POC and VSS in TOC2 was high and the POC was about 4.4 fold that of the VSS. Consequently, TOC 2 without dilution effect was assessed as a proper method to increase the analyzing accuracy of swine manure including high solid organics.

Dissolved organic carbon, DOC, Particulate organic carbon, POC, Swine manure, Total organic carbon, TOC

배병욱 Byung Uk Bae , 남윤우 Youn Woo Nam

DOI:10.15681/KSWE.2014.30.5.517 Vol.30(No.5) 517-523, 2014

In order to remove both nitrate and sulfate present in the concentrate of RO(reverse osmosis) process, a combined bio-regeneration and ion-exchange(IX) system was studied. For this purpose, both denitrifying bacteria(DNB) and sulfate reducing bacteria(SRB) were simultaneously cultivated in a bio-reactor under anaerobic conditions. When the IX column containing a nitrate-selective A520E resin was fully exhausted by nitrate and sulfate, the IX column was bio-regenerated by pumping the supernatant of the bio-reactor, which contains MLSS concentration of 125±25 mg/L, at the flowrate of 360 BV/hr. Even though the nitrate-selective A520E resin was used, the breakthrough curves of ionic species showed that sulfate was exhausted earlier than nitrate. The reason for this result is due to the fact that the concentration of sulfate in RO concentrate was 36 to 48 times higher than nitrate. The bio-reactor was successfully operated at a volumetric loading rate of 0.6 g COD/l·d, nitrate-N loading rate of 0.13 g NO3--N/l·d, and sulfate loading rate of 0.08 g SO42-/l·d. The removal rate of SCOD, nitrate-N, sulfate was 90, 100, and 85%, respectively. When the virgin resin was fully exhausted and consecutively bio-regenerated for 2 days, 81% of nitrate and 93% of sulfate were reduced. When the virgin resin was repeatedly used up to 4 cycles of service and bio-regeneration, the ion-exchange capacity of bio-regenerated resin decreased to 95, 91, 88, and 81% of virgin resin.

Bio-regeneration, Denitrification, Ion-exchange technology, Oxidation reduction potential, RO concentrate, Sulfate reduction

최인철 In Cheol Choi , 안태웅 Tae Ung Ahn , 유순주 Soon Ju Yu , 정현미 Hyen Mi Chung , 권오상 Oh Sang Kwon , 김원기 Won Ky Kim , 염익태 Ick Tae Yeom , 손대희 Dae Hee Son

DOI:10.15681/KSWE.2014.30.5.524 Vol.30(No.5) 524-531, 2014

Korea has been trying to manage water quality of rivers and lakes in many ways. Ministry of Environment is making continuous efforts of operation control improvement such as strengthening effluent standards in sewage treatment plants and expanding Tele-Monitoring System (TMS). However, evaluation method for operations of sewage treatment plants and establishment system of effluent standards are inadequate. The objective of this study is to evaluate for operations of sewage treatment plants using statistics technique such as frequency analysis, percentile, normal distribution analysis. We used the effluent data (BOD, COD, SS) collected at 299 plants in 2012. The values were very low by comparison with standards. The Data followed a normal distribution. We think that distribution characteristics are closely related with effluent standards, especially T-P and BOD. Statistics technique attempted in this study can be used to evaluate for operations of sewage treatment plants and assess the appropriateness of effluent standards based on TBEL(Technology-based effluent limitation). And, this technique can be used to figure out the overall level of plants, the status of each plant and the favorable treatment process for each item (BOD, COD etc.). Data acquired through this method can be used to improve facilities and operation techniques and decide on a sewerage policy.

Evaluation for operations, Frequency analysis, Normal distribution analysis, Percentile, Public sewage treatment plants, PSTPs, Statistics technique

최종수 Jong Soo Choi , 공영산 Young San Kong , 이정민 Jung Min Lee , 방기웅 Ki Woong Bang

DOI:10.15681/KSWE.2014.30.5.532 Vol.30(No.5) 532-538, 2014

A cylinder-shaped filter was developed to manage the runoff from construction sites. Compressed air was used for back- washing and pore sizes of filter were 23μm and 46μm. The turbid water was prepared using sediments in construction sites. The grain size analysis showed that grains smaller than 38μm and larger than 335μm in size constituted 34.4% and 37.6%, respectively. Removal efficiency of the filter on turbidity, SS, COD, TN and TP showed 25~37%, 20~40%, 50~55%, 23~27% and 14~20%, respectively, whereas their removal efficiecy by using coagulant PAC showed 77~84%, 70~83%, 53~60%, 27~36%, and 59~75%, respectively. The filtration time was determined to be around 10 to 20 minutes. Back-washing for 10 seconds by pressurized air resulted in a satisfactory regeneration efficiency. According to the aforementioned test results, the cylinder- shaped filter is effective in reducing turbidity and would be suitable for practical application in construction sites and farms.

Back-wash, Coagulant, Construction site, Cylinder-shaped filter, Runoff

유재정 Jae Jeong Yu , 이혜진 Hae Jin Lee , 이경락 Kyung Lak Lee , 이인정 In Jeong Lee , 정강영 Gang Young Jung , 천세억 Se Uk Cheon

DOI:10.15681/KSWE.2014.30.5.539 Vol.30(No.5) 539-548, 2014

This study was carried out to investigate algal community structures and their correlations with environmental factors on five weir areas in the Nakdong River, South Korea. Water qualities, hydrodynamics, meteorological conditions and algal species compositions were observed in studied sites from May 2010 to Dec. 2013. Results showed that average total phosphorus concentration of 2013 was decreased by 52.4% in comparing with that from 2010 to 2011. Chlorophyll.a concentrations were positive significant with water temperature, pH, total phosphorus and total nitrogen, but is not significant with turbidity and suspended solids. Seasonal successions of algae were observed that Stephanodiscus sp. was dominant species with 65.3% of dominant frequency in studied site. Large algal biomass of the low temperature-adapted diatoms were observed during temperature range of 4~9°C, but large cyanobacterial biomass mainly during high temperature period ranged from 22°C to 32°C. Microcystis sp. dominated during high water temperature in summer. The yearly correlations of algal biomass with accumulated solar radiations were not significant but seasonal correlations of summer from June to August were significant with correlation coefficient 0.33 (p<0.05). There were not significant correlations between turbidities and algal biomass. Turbidity and suspended solids concentrations were not significant correlation with algal biomass. According to the results, algal communities had strong correlation with water temperature and had partially correlation with solar radiation. For an effective management of algal blooms, water managers should survey with more long-term monitoring of various environmental factors and algal communities.

Algae community, Cyanobacterial bloom, Environment factors, Eutrophic, Nakdong River, Water environment

이지민 Ji Min Lee , 박윤식 Youn Shik Park , 정영훈 Young Hun Jung , 조재필 Jae Pil Cho , 양재의 Jae Eui Yang , 이관재 Gwan Jae Lee , 김기성 Ki Sung Kim , 임경재 Kyoung Jae Lim

DOI:10.15681/KSWE.2014.30.5.549 Vol.30(No.5) 549-558, 2014

Occurrence frequency of flood and drought tends to increase in last a few decades, leading to social and economic damage since the abnormality of climate changes is one of the causes for hydrologic facilities by exceedance its designed tolerance. Soil and Water Assessment Tool (SWAT) model was used in the study to estimate temporal variance of groundwater recharge and baseflow. It was limited to consider recession curve coefficients in SWAT model calibration process, thus the recession curve coefficient was estimated by the Baseflow Filter Program (BFLOW) before SWAT model calibration. Precipitation data were estimated for 2014 to 2100 using three models which are GFDL-ESM2G, IPSL-CM5A-LR, and MIROC-ESM with Representative Concentration Pathways (RCP) scenario. SWAT model was calibrated for the Soyang watershed with NSE of 0.83, and R2 of 0.89. The percentage to precipitation of groundwater recharge and baseflow were 27.6% and 17.1% respectively in 2009. Streamflow, groundwater recharge, and baseflow were estimated to be increased with the estimated precipitation data. GFDL-ESM2g model provided the most large precipitation data in the 2025s, and IPSL-CM5A-LR provided the most large precipitation data in the 2055s and 2085s. Overall, groundwater recharge and baseflow displayed similar trend to the estimated precipitation data.

Baseflow, Climate change, Groundwater, RCP Scenario, SWAT

최정수 Jung Su Choi , 김현구 Hyun Gu Kim , 주현종 Hyun Jong Joo

DOI:10.15681/KSWE.2014.30.5.559 Vol.30(No.5) 559-567, 2014

Since the ocean dumping of organic wastes is prohibited under the London Convention, the need for land treatment of food waste leachate (FWL) has significantly been growing in recent years. This study was conducted to use thermal solubilization to turn FWL into a form that can easily be degraded during the anaerobic digestion process, thereby reducing the percentage of solids and increasing the production of methane. To derive the optimal operating conditions of thermal solubilization, a laboratory-scale reactor was built and operated. The optimal reaction temperature and time turned out to be 190°C and 90 min, respectively. The BMP test showed a methane production of 465 mL CH4/g CODCr and a biodegradation rate of 90.1%. The production of methane rose by about 15%, compared with no the application of thermal solubilization. To reduce the solid content of FWL and improve the methane production, therefore, it may be helpful to apply thermal solubilization to pre-treatment facilities for anaerobic digestion.

Food waste leachate, Methane production, Solid reduction, Thermal solubilization