윤석제 Seok Jea Youn , 임종권 Jong Kwon Im , 변명섭 Myeong-seop Byeon , 유순주 Soon Ju Yu

DOI:10.15681/KSWE.2019.35.2.99 Vol.35(No.2) 99-104, 2019

The objective of this study was to investigate the relationship between the biomass of cyanobacteria and the concentration of 2-methylisoborneol (2-MIB) in the lower Gongji stream. The investigation was done using a field study that was conducted from 2015 to 2017. The 2-MIB concentration in the lower Gongji stream ranged from 0 to 153 ng/L, while the upper stream had 0 2-MIB concentration. 3 genera (Oscillatoria, Phormidium, Pseudanabaena) of cyanobacteria were detected in the lower Gongji stream with 2-MIB concentration. Among these 3 genera, an increase in Phormidium, Pseudanabaena biomass was associated with an increase in 2-MIB concentration. Accordingly, Phormidium, Pseudanabaena were regarded as the biological source of 2-MIB in that area. In October 2017, although planktonic cyanobacteria occurred less frequently, many benthic cyanobacteria mats were observed on the surface of the water body. Therefore, the high 2-MIB concentration, which exceeded 110 ng/L, can likely be attributed to the benthic cyanobacteria. In a laboratory experiment, individual Oscillatoria filaments were aggregated to form a colony with a higher density. This colony tended to float on the water surface. Cyanobacteria mats after floating aggregated mats were distributed in a net shape on the bottom.

2-MIB, Benthic cyanobacteria, Cyanobacteria, Oscillatoria, Pseudanabaena

이보미 Lee Bo-Mi , 성기선 Seon Seong-Ki , 김국회 Kim Guk-Hui , 문권영 Moon Gwon-Young , 신명철 Shin Myoung-Chul , 홍정기 Hong Jung-Ki , 김갑순 Kim Kap-Soon , 유순주 Yu Soon-Ju , 허인애 Huh In-Ae , 노혜란 Noh Hye-Ran

DOI:10.15681/KSWE.2019.35.2.105 Vol.35(No.2) 105-114, 2019

The objective of this study was to investigate the pollution assessment of organic matters, nutrients, and metals in sediment in major lakes (5 lakes and 17 sites) of Buk-han river using various sediment pollution assessment guidelines and indices. The concentrations of organic matters and nutrients were lower than class IV (Sediment pollution assessment guidelines of Korea) and Severe Effect Level (SEL, Sediment pollution assessment guidelines of Ontario). This results indicated that the lakes sediments were unpolluted and tolerable level for sediment dwelling organisms by organic matters and nutrients. However, several sites of Chuncheon and Soyang lakes were evaluated “heavily polluted” level by organic index (Org-index). The order of lakes by metals concentrations from the one with the highest concentration was Hwacheon, Chuncheon, Cheongpyeong, Uiam, Soyang. All lakes except Hwacheon were assessed unpolluted to marginally and tolerable level for sediment dwelling organisms by metals based on sediment pollution assessment guidelines (Korean and Ontario), indices of geoaccumulation (Igeo), pollution loading (PLI) and ecological risk (RI). In Lake Hwacheon, every investigated sites were polluted with metals, especially Hg, based on sediment pollution assessment guideline of Korea and indices (Igeo, PLI and RI). The dwelling organisms in sediment of Hwacheon Lake were likely to be severed by metals.

Buk-han river, Lake, Metals, Organic matter, Pollution assessment, Sediment

이덕영 Dukyoung Lee , 손영규 Younggyu Son

DOI:10.15681/KSWE.2019.35.2.115 Vol.35(No.2) 115-122, 2019

The objective of this study was to investigate the sonophysical and sonochemical effects induced by acoustic cavitation in heterogeneous systemin a 28 kHz double-bath reactor using calorimetry, the aluminiumfoil erosion test, and the luminol test. With no glass beads, calorimetric power in the inner vessel increased as much as the outer sonoreactor lost and total calorimetric power was maintained for various liquid height conditions (0.5 ~ 7 cm) in the vessel. Higher calorimetric energy was obtained at higher liquid height conditions. Similar results were obtained when glass beads were placed with various beads heights (0.5 ~ 2.0 cm) and relatively high calorimetric energy was obtained in spite of large attenuation in the glass beads layer. An aluminium foil placed between the bottom of the inner vessel and the glass beads layer was damaged, indicating significant sonophysical effects. Much less damage was detected when the foil was placed above the beads layer due to large attenuation of ultrasound. Sonochemical effects, visualized by sonochemiluminescence (SCL), also decreased significantly when the beads were placed in the vessel. It was established that the optimization of the liquid height above the solid-material layer could enhance the sonophysical and sonochemical effects in the double-bath sonoreactors.

Calorimetry, Cavitation, Heterogeneous system, Sonochemical effects, Sonochemiluminescence (SCL), Sonophysical effects

정명화 Myung-hwa Jeong , 권동현 Dong-hyun Kwon , 임연주 Yeon-ju Lim , 안종화 Johng-hwa Ahn

DOI:10.15681/KSWE.2019.35.2.123 Vol.35(No.2) 123-130, 2019

Ethylenediaminetetraacetic acid-modified bentonite (EMB) was used for adsorption of zinc ion (Zn) from aqueous solution, compared with unmodified bentonite (UB). Parameters such as dose (0.750 ~ 3.125 g/L), mixing intensity (10 ~ 150 rpm), contact time (0.17 ~ 30 min), pH (2 ~ 7), and temperature (298 ~ 338 K), were studied. Zn removal efficiency for EMB was 20 ~ 30 % higher, than that for UB, in all experiments. Thermodynamic studies demonstrated that adsorption process was spontaneous with Gibb’s free energy (ΔG) values, ranging between -5.211 and -7.175 kJ/mol for EMB, and -0.984 and -2.059 kJ/mol for UB, and endothermic with enthalpy (ΔH) value of 9.418 kJ/mol for EMB and 7.022 kJ/mol for UB. Adsorption kinetics was found to follow the pseudo-second order kinetics model, and its rate constant was 3.41 for EMB and 2.00 g/mg min for UB. Adsorption equilibrium data for EMB were best represented by the Langmuir adsorption isotherm, and calculated maximum adsorption capacity was 2.768 mg/g. It was found that the best conditions for Zn removal of EMB within the range of operation used, were 3.125 g/L dose, 90 rpm intensity, 10 min contact time, pH 4, and 338 K. Therefore, EMB has good potential for adsorption of Zn.

Adsorption, EDTA-modified bentonite, Operation condition, Zinc ion

정의상 Euisang Jeong , 조홍래 Hong-lae Cho

DOI:10.15681/KSWE.2019.35.2.131 Vol.35(No.2) 131-144, 2019

Climate Change affects the hydrological cycle in agricultural watersheds through rising air temperature and changing rainfall patterns. Agricultural watersheds in Korea are characterized by extensive paddy fields and intensive water use, a resource that is under stress from the changing climate. This study analyzed the effects of climate change on river flows for Geum Cheon and Eun-San Choen watershed using STREAM, a semi-distributed watershed model. In order to evaluate the performance and improve the reliability of the model, calibration and validation of the model was done for one flow observation point and three reservoir water storage ratio points. Climate change scenarios were based on RCP data provided by the Korea Meteorological Administration (KMA) and bias corrections were done using the Quantile Mapping method to minimize the uncertainties in the results produced by the climate model to the local scale. Because of water mass-balance, evapotranspiration tended to increase steadily with an increase in air temperature, while the increase in RCP 8.5 scenario resulted in higher RCP 4.5 scenario. The increase in evapotranspiration led to a decrease in the river flow, particularly the decrease in the surface runoff. In the paddy agricultural watershed, irrigation water demand is expected to increase despite an increase in rainfall owing to the high evapotranspiration rates occasioned by climate change.

Agriculture, Climate Change, Irrigation, Watershed Model

임병란 Lim Byung Ran , 김희서 Kim Hee Seo , 고연실 Go Yeon Sil , 김현갑 Kim Hyun Kab , 김종학 Kim Jong Hak , 이태진 Lee Tae Jin

DOI:10.15681/KSWE.2019.35.2.145 Vol.35(No.2) 145-151, 2019

The purpose of this study was to investigate treatment characteristics of diatomite filtration, that would allow water recovery from biologically-treated effluent for reuse. Diatomite, Celpure 100, and acid clay were used as filter-aids, with a support filter manufactured from polyethylene (PE), and polypropylene (PP). This pre-coating process using diatomite filter-aids, is used in the filtration range of pressure filters, and has consistently provided high-quality separation. The results showed that variations in average removal efficiency of SS, and T-P from biologically treated effluent by the diatomite-coated PE filter, were approximately 82.2 ~ 88.9 % and 4.8 ~ 21.1 %, respectively. T-P treatment efficiency of the PP filter pre-coated with diatomite and Celpure^Ⓡ100 at 57.64 g/m², was approximately 24 ± 10 % and 40 ± 15 % on average, respectively. Particle size distribution of secondary effluent varied from 0.05 to 200 μm, and d50 value was 20.76 μm. The size distribution of particles in the diatomite filtrate ranged from 1.26 to 101.1 μm when pre-coated with diatomite filter-aid, at a content of 57.64 g/m². Diatomite filter aids, i.e., the particles that form the pre-coating layer, capture very fine particles as well as macromolecules, owing to their complex structure with numerous fine microscopic pores, and surface properties. The filtration process using diatomite and CelpureⓇ100 as filter aids, has been successfully applied, to recover water from sewage for reuse. The disadvantage of the process, is that the particle size of the filter-aid is spent, because of pressurization.

Diatomite, Filter-aids, Filtration, Treatment characteristics, Sewage reuse

공동수 Dongsoo Kong , 민정기 Jeong-ki Min , 노성유 Seong-yoo Noh

DOI:10.15681/KSWE.2019.35.2.152 Vol.35(No.2) 152-164, 2019

In this study, a Benthic Macroinvertebrates Family Index (BMFI) was developed using 100 indicator groups (99 families including Chironomidae with 2 phena). Families were assigned a score between 1 and 10 depending on their sensitivity to organic pollution. The BMFI was composed of the sensitivity and relative abundance of the indicator taxa. Sensitivity values of each group were generally similar to Biological Monitoring Working Party (BMWP) scores or Walley, Hawkes, Paisley, Trigg (WHPT) scores of UK, Japanese BMWP scores, and the FBI tolerance values of North America. However, sensitivity values of some taxa were significantly different from those of foreign countries, which seemed to have resulted from discrepancy in species composition, difference of taxonomic classification system, or methodological difference for estimation of sensitivity. As an annual average level, BMFI showed significant correlation with concentration of 5-day biochemical oxygen demand (BOD5) (correlation coefficient r = -0.80, n = 569 sites), total suspended solids (r = -0.68), and total phosphorus (r = -0.79). In addition, BMFI revealed strong correlation with Shannon-Weaver's species diversity (r = 0.85), Margalef's species richness (r = 0.85) and McNaughton's dominance (r = -0.84). Correlation between BMFI and water quality parameters or community indices such as species diversity did not show significant difference compared to that of species-level indices such as BMI (Benthic Macroinvertebrates Index). This means that BMFI is a more useful indicator in terms of easy identification of organisms. BMFI was used to assess the environmental status of 3,017 sites of Stream Ecosystem Survey conducted by the Korean Ministry of Environment between 2016 and 2018. As a result, about half of all sites appeared to be in good condition, and a quarter in poor condition.

Benthic macroinvertebrates, Biological assessment, Indicator, Family-level biotic index, Rapid bioassessment

공동수 Dongsoo Kong

DOI:10.15681/KSWE.2019.35.2.165 Vol.35(No.2) 165-180, 2019

Water quality data of 81 lakes in Korea, 2013 ~ 2017 were analyzed. Most water quality parameters showed left-skewed distribution, while dissolved oxygen showed normal distribution. pH and dissolved oxygen showed a positive correlation with organic matter and nutrients, which appeared to be a nonsense correlation mediated by the algae. The ratio of BOD₅ and COD_Mn to CBOD was 21 % and 52 % in the freshwater lakes, respectively. TOC concentration appeared to be underestimated by the UV digestion method, when salinity exceeds 700 μS cm^-1. In terms of nitrogen/phosphorus ratio, the limiting factor for algal growth seemed to be phosphorus in most of the lakes. Chlorophyll α increased acutely with decrease of N/P ratio. However, it seemed to be a nonsense correlation mediated by phosphorus concentration, since the N/P ratio depended on phosphorus. The N/P ratio of brackish lakes was lower than that of the freshwater, at the same concentration of phosphorus. It is worth examining denitrification that occurs, in bottom layer and sediment, during saline stratification. Chl.α concentration decreased in the form of a power function with increase of mean depth. The primary reason is that deep lakes are mainly at the less-disturbed upstream. However, it is necessary to investigate the effect of sediment, on water quality in shallow lakes. Light attenuation in the upper layer, was dominated by tripton (non-algal suspended solids) absorption/scattering (average relative contribution of 39 %), followed by CDOM (colored dissolved organic matter) (average 37 %) and Chl.α (average 21 %).

BOD₅, COD_Mn, Korean lakes, Lake classification, Light attenuation, Limiting factor, TOC, Water Quality