• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.251-255
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• 2002

Eutrophic matters accumulated on the bottom of sea, river and lake cause red tide phenomenon in ocean and outbreak green algae in river and lake. Systems are developed to remove the noxious deposit. But the existing systems remove not only the eutrophic matters but also natural materials, sand, pebbles etc. that should remain at the bottom. This paper describes a new system that can safely, and economically take away the noxious deposit in underwater. High pressure water jet is used to induce vortices in the triangular suction section, and air-lifting pump to lift up the deposit. The mixture of the water and deposit is filtered through the drum filters. An under camera shows the under water situation along the moving direction of the system that is controlled by a remote operator. This remote controlled moving system obliterate the necessity of the diver that usually costs high. The experimental results show the effectiveness of the suggested system.

• ALGAE
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• v.21 no.3
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• pp.311-316
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• 2006

The effects of light quality and irradiance on the growth of Cochlodinium polykrikoides were investigated in the laboratory. At 25°C and 30 psu the irradiance-growth curve was described as μ = 0.34 (I-9.76)/(I+12.5), (r=0.98). This suggests half-saturation photon flux density (PFD) (Ks) of 32.0 μmol photons m–2 s–1, and a compensation PFD (Ic) of 9.76 μmol photons m–2 s–1. Because the Ic equates to a depth of ca. 15.4 m, these responses suggest that irradiance at the depth around and below the thermocline in Yeosuhae Bay would provide favorable conditions for C. polykrikoides. Photoinhibition did not occur at 300 μmol photons m–2 s–1, which was the maximum irradiance used in this study. Blue (450 nm), yellow (590 nm) and red (650 nm) light had different effects on the growth of C. polykrikoides: it grew well under blue light, but not under yellow light. This implies that C. polykrikoides is more likely to cause an outbreak of red tide in the open sea where blue-green wavelengths predominate, rather than in enclosed water bodies where suspended particles absorb most of the blue wavelengths, and yellow-orange wavelengths predominate.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.53-59
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• 2018

Water pollution is drastically increasing day by day, because of the enhancement in use of livestock, urban sewage detergents and fertilizers. Moreover increase in concentration of phosphorous and nitrogen contained in sewage, leads to green tide problem in the rivers and causes marine pollution. For this problem to solve, several technologies are being researched and developed. Among them, this experiment is a study on Bench-scale STP based on internationally certified sewage treatment equipment by MEPC. 227(64) of IMO. The purpose of this study is to compare the biological treatment efficiency of phosphorus of Bench-scale STP. The ratio of C : N : P was set to 10 : 5 : 3 and 10 : 3 : 1 as the operating conditions. And the operation cycle was set to anoxic(mixed) 70 min - aeration 50 min (70-50), anoxic(mixed) 90 min - aeration 60 min (90-60). As a result, the phosphorous treatment efficiency was 88% at average, and the treatment efficiency was steady at 90-60 better than 70-50. The efficiency of the bench-scale STP has been verified through this experiment and additional experiments are required to derive the optimal operating conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.427-431
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• 1999

This study was conducted to investigate the inhibitory activity of water extracts and its enzymatic hydrolysates from algae against angiotensin-I converting enzyme (ACE). The 7 kinds of algae were extracted with water at $50^{\circ}C,\;70^{\circ}C$ and $98^{\circ}C$. ACE inhibitory activities of water extracts were the highest at $70^{\circ}C$, and those of ceylon moss, layer, green layer, sea mustard, seaweed fusiforme sea tangle and sea staghorn were $10.9\%,\;9.3\%,\;8.9\%,\;8.2\%,\;7.5\%,\;7.1\%$ and $7.0\%$, respectively. Layer, green laver sea mustard and ceylon moss of high ACE inhibitory activities among the 7 kinds of water extracts were hydrolyzed by maxazyme and papain during 24hrs. ACE inhibitory activity of enzymatic hydrolysates was higher than that of water extracts, and was the highest in enzymatic hydrolysates of laver among the tested samples. In laver hydrolysates by proteases, the highest ACE inhibitory activity and peptide-nitrogen contents were observed at 8 hours hydrolysis and the hydrolysates by maxazyme showed relatively higher activity than those by papain(31.3 and $27.9\%$, respectively). But peptide-nitrogen contents were greater in papain hydrolysates than in maxazyme.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.46-56
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• 2018

A mcyB-specific Ultra-Rapid quantitative PCR was developed for the quantitative detection of Microcystis aeruginosa, which is often a dominant species in green tide. McyB-specific UR-qPCR was optimized under extremely short times of each step in thermal cycles, based on the specific primers deduced from the mcyB in microcystin synthetase of M. aeruginosa. The M. aeruginosa strain KG07 was used as a standard for quantification, after the microscopic counting and calculation by mcyB-specific UR-qPCR. The water samples from the river water with the Microcystis outbreak were also measured by using both methods. The $1.0{\times}10^8$ molecules of mcyB-specific DNA was recognized inner 4 minutes after beginning of UR-qPCR, while $1.0{\times}10^4$ molecules of mcyB-specific templates was detected inner 7 minutes with quantitative manner. From the range of $1.0{\times}10^2$ to $1.0{\times}10^8$ initial molecules, quantification was well established based on $C_T$ using mcyB-specific UR-qPCR (Regression coefficiency, $R^2=0.9977$). Between the numbers of M. aeruginosa cell counting under microscope and calculated numbers using mcyB-specific UR-qPCR, some differences were often found. The reasons for these differences were discussed; therefore, easy compensation method was proposed that was dependent on the numbers of the cell counting. Additionally, to easily extract the genomic DNA (gDNA) from the samples, a freeze-fracturing of water-sample using liquid nitrogen was tested, by excluding the conventional gDNA extraction method. It was also verified that there were no significant differences using the UR-qPCR with both gDNAs. In conclusion, the mcyB-specific UR-qPCR that we proposed would be expected to be a useful tool for rapid quantification and easy monitoring of M. aeruginosa in environmental water.

• Journal of Wetlands Research
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• v.15 no.2
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• pp.251-264
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• 2013

There are some factors affecting the shorebirds in selecting a coastal inland roost site where they have to stay during the high tide when the entire intertidal zone is covered with water. We investigated eight species (Eastern Curlews Numenius madagascariensis, Green Shanks Tringa nebularia, Bar-tailed Godwits Limosa lapponica, Grey Plovers Pluvialis squatarola, Dunlins Calidris alpine, Whimbrels Numenius phaeopus, Eurasian Curlews Numenius arquata and Terek Sandpipers Xenus cinereus) to identify the spatial and temporal variability in coastal inland roost use in the area and the factors influencing the use. We considered the area and length of the standing water in the roost site, temperature, wind speed, the time of migration and the intensity of disturbance. As a result, number of individuals and type of species using the roost site varied across spatial and temporal scales. And the factors affecting the roost use was species-specific. The roost site of the study area was a closed shrimp farm however, it has been converted to a Salicornia herbacea, a salt marsh plant, farm recently. In a situation where coastal inland roost site is needed, we hereby describe a resolution for the juxtaposition of shorebirds and farming.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.214-218
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• 2014

We introduce a technical equipment of GATe (Green (algae)-tide) water combine developed by K-water. The GATe water combine consists of five modules: main body and buoyant, transfer hopper, screen conveyer, sludge remover, and separator of algae and waste. Also a sprinkler, as the pre-treatment step if necessary, is equipped to the device to spread out environmental-friendly algaecide under the circumstance that the level of algal bloom does not reach to the scum-forming condition. The overall module system of this device is very simple. Based on the field test, the device covers surface area of ca. $500,000m^2day^{-1}$ during the period from May to July, and treats water volume as much as $500,000m^3day^{-1}$ in spite of some variation depending on the water quality condition. The removal efficiency of the device appeared to be over 90%. In addition, the operating duration of the device was able to expand to cover the period between March and November. We expect this new technology can be used to solve algal bloom problems in drinking water resource and public water area.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.56-61
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• 2009

Paradigm depending only on fossil fuel for building heat source is rapidly changing. Accelerating the change, as it has been known, is obligation for reducing green house gas coming from use of fossil fuel, i.e. reaction to United Nations Framework Convention on Climate Change. In addition, factors such as high oil price, unstable supply, weapon of petroleum and oil peak, by replacing fossil fuel, contributes to advance of environmental friendly renewable energy which can be continuously reusable. Therefore, current new energy policies, beyond enhancing effectiveness of heat using equipments, are to make best efforts for national competitiveness. Our country supports 11 areas for new renewable energy including sun light, solar heat and wind power. Among those areas, ocean thermal energy specifies tidal power generation using tide of sea, wave and temperature differences, wave power generation and thermal power generation. But heat use of heat source from sea water itself has been excluded as non-utilized energy. In the future, sea water heat source which has not been used so far will be required to be specified as new renewable energy. This research is to survey local heating system in Europe using sea water, central solar heating plants, seasonal thermal energy store and to analyze large scale central solar heating plants in German. Seasonal thermal energy store necessarily need to be equipped with large scale thermal energy store. Currently operating central solar heating system is a effective method which significantly enhances sharing rate of solar heat in a way that stores excessive heat generating in summer and then replenish insufficient heat for winter. Construction cost for this system is primarily dependent on large scale seasonal heat store and this high priced heat store merely plays its role once per year. Since our country is faced with 3 directional sea, active research and development for using sea water heat as cooling and heating heat source is required for seashore villages and building units. This research suggests how to utilize new energy in a way that stores cooling heat of sea water into seasonal thermal energy store when temperature of sea water is its lowest temperature in February based on West Sea and then uses it as cooling heat source when cooling is necessary. Since this method utilizes seasonal thermal energy store from existing central solar heating plant for heating and cooling purpose respectively twice per year maximizing energy efficiency by achieving 2 seasonal thermal energy store, active research and development is necessarily required for the future.

• Weed & Turfgrass Science
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• v.6 no.3
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• pp.222-234
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• 2017

Green tides, which was mainly caused by Ulva spp., have been increasing in severity and frequency globally, and have negatively affected on marine ecosystems. This study was conducted to investigate effects of various physical and chemical factors on the death of Ulva australis (ULAUS) and to consider a practical measures useful for alleviating Ulva bloom. Soaking of ULAUS thalli in pure water for 8 hr didn't induce a death, but incubation in 1.0-1.5% salinity for 7 d inhibited sporulation by about 70%. Desiccation gave rise to a serious damage when more than 40-50% of initial fresh weight was lost. ULAUS growth was sensitive to temperature and seriously inhibited from more than $30^{\circ}C$. At $35^{\circ}C$, $40^{\circ}C$, $45^{\circ}C$ and $50^{\circ}C$, treatment time required for 90-95% death of ULAUS thalli was 1 d, 10 min, 30 sec, and 1 sec, repectively. ULAUS growth was seriously inhibited at lower than pH 6.0 and completely dead at pH 4.0. Several compounds for ULAUS control was selected and the chemcals causing a rapid death were oxidants such as hydrogen peroxide and sodium percarbonate. Taken together, our results suggest that low salinities, dryness, pH, high temp. and compounds could be selected for Ulva bloom control, and high temperature and compounds seems to be useful for a development of practical control methods.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.1-15
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• 2017

Daecheong Reservoir was made by the construction of a large dam (>15 m in height) on the middle to downstream of the Geum River and the discharge systems have the watergate-spillway (WS), a hydropower penstock (HPP), and two intake towers. The purpose of this study was to investigate the limnological anomalies of turbid water reduction, green algae phenomenon, and oligotrophic state in the lower part of reservoir dam site, and compared with hydro-meteorological factors. Field surveys were conducted in two stations of near dam and the outlet of HPP with one week intervals from January to December 2000. Rainfall was closely related to the fluctuations of inflow, outflow and water level. The rainfall pattern was depended on the storm of monsoon and typhoon, and the increase of discharge and turbidity responded more strongly to the intensity than the frequency. Water temperature and DO fluctuations within the reservoir water layer were influenced by meteorological and hydrological events, and these were mainly caused by water level fluctuation based on temperature stratification, density current and discharge types. The discharges of WS and HPP induced to the flow of water bodies and the outflows of turbid water and nutrients such as nitrogen and phosphorus, respectively. Especially, when hypoxic or low-oxygen condition was present in the bottom water, the discharge through HPP has contributed significantly to the outflow of phosphorus released from the sediment into the downstream of dam. In addition, HPP effluent which be continuously operated throughout the year, was the main factor that could change to a low trophic level in the downreservoir (lacustrine zone). And water-bloom (green-tide) occurring in the lower part of reservoir was the result that the water body of upreservoir being transported and diffused toward the downreseroir, when discharging through the WS. Finally, the hydropower effluent was included the importance and dynamics that could have a temporal and spatial impacts on the physical, chemical and biological factors of the reservoir ecosystem.