• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.90-103
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• 2014

Distribution characteristics of water masses, dissolved inorganic and organic nutrients were investigated in the southern part of the East Sea of Korea in September, 2011. On the basis of the vertical profiles of temperature, salinity and dissolved oxygen, water masses in the study area were divided into 4 major groups, such as WM (water mass)-I, WM-II, WM-III, WM-IV. Their characteristics were similar to Tsushima Surface Water (TSW), Tsushima Middle Water (TMW), North Korea Cold Water (NKCW) and East Sea Proper Water (ESPW), respectively. In the vertical profiles of dissolved nutrients, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) concentrations were highest in the WM-IV, followed by WM-III, WM-II, WM-I. On the contrary, distribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) were highest in the WM-I, followed by WM-II, WM-III, WM-IV. Although the DIN : DIP ratio in all of the water masses was similar to Redfield ratio(16), the DIN : DIP ratio in mixed layer was about 5.3, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. However, the DON proportion in dissolved total nitrogen (DTN) was about 70% in the mixed layer where inorganic nitrogen is limiting factor. Thus, enriched DON may play an important source of the nutrient for the growth of phytoplankon in the East Sea.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.228-234
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• 2004

Dissolved air flotation (DAF), in which suspended solids are removed from water by means of micro-size air bubbles raising slowly up in water and lifting solids from water (smaller than those) attached onto the micro-bubbles as well as those (larger than solids) being attached on these, have been used in water and wastewater since 1920s. The dissolved air flotation technology was originally based on the laminar flow conditions prevailing in water to be treated, but the latest development in that technology has led now to a situation, in which the flow conditions may also be turbulent ones in the modem dissolved air flotation units. Despite of that, the flotation phenomenon used in this unit operation for removal suspended solids from water or wastewater is still the same.

• Journal of Soil and Groundwater Environment
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• v.20 no.4
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• pp.31-40
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• 2015

Various types of inorganic and organic colloids are present in natural water including groundwater. Previous studies showed that Fe, Mn and Al are colloid-forming elements and dissolved concentrations can be erroneous for these elements if water samples are not properly filtered. Dissolved concentrations of elements including Ca, Na, Mg, K, Fe, Mn, Si and Al in groundwater from alluvial and bedrock aquifers, and surface water near Nakdong River were determined to evaluate effects of colloids on dissolved concentrations in natural water samples using various pore sizes of filters. Groundwater is mostly anoxic and have elevated concentrations of Fe and Mn, which provides a unique opportunity to observe the effects of colloids on dissolved concentrations of colloid-forming elements. Membrane filters with four kinds of pore sizes of 1000 nm, 450 nm, 100 nm, and 15 nm were used for filtration of water samples. Concentrations of dissolved concentrations in each filtrate did not show significant differences from 1000 nm to 100 nm. However, concentrations of all elements considered were decreased in the filtrates obtained using 15 nm pore size filters by 10 to 15% compared to those using 450 nm except for bedrock groundwater. Al in surface water showed a distinct linear decrease with the decrease of filter pore sizes. These results showed that 100 nm pore size had little effect to remove colloidal particles in alluvial groundwater and surface water in our study. In contrast, significant concentration decreases in 15 nm pore size filtrates indicate that the presence of 15 to 100 nm colloidal particles may affect determination of dissolved concentrations of elements in natural water.

• Journal of Ecology and Environment
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• v.30 no.3
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• pp.209-223
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• 2007

Twenty-four wetlands located in Higashi-Hiroshima City in West Japan were selected for this study in order to investigate both the relationship between aquatic plant composition and environmental conditions; and the relationship between changing land use patterns in the catchments and the concentration of different forms of nitrogen in the wetlands. The dominant and subdominant species which comprised the principal vegetation were determined based on a vegetation census conducted in each wetland during the growing season from June to August, 2006. The seasonal variations of water quality factors (pH, electrical conductivity, turbidity, dissolved oxygen, total dissolved solid, and temperature) and different forms of nitrogen such as nitrite, nitrate, ammonium, total nitrogen, dissolved organic nitrogen and dissolved inorganic nitrogen concentrations were analyzed as important indicators of water quality for the surface water of the wetlands. The surveyed wetlands were classified into three types (non-disturbed wetlands, moderately-disturbed wetlands and highly-disturbed wetlands), based on the degree of human disturbance to their catchment areas. An analysis of variance indicated that there was a significant difference among the wetland groups in the annual mean values of electrical conductivity, total dissolved solids, total nitrogen, nitrite, dissolved inorganic nitrogen and dissolved organic nitrogen. Classification of the wetlands into three groups has revealed a pattern of changes in the composition of plant species in the wetlands and a pattern of changes in nitrogen concentrations. A majority of the non-disturbed wetlands were characterized by Brasenia schrebi and Trapa bispinosa as dominant; with Potamogeton fryeri and Iris pesudacorus as sub-dominant species. For most of the moderately-disturbed wetlands, Brasenia schrebi were shown to be a dominant species; Elocheriss kuriguwai and Phragmites australis were observed as sub-dominant species. For a majority of the highly-disturbed wetlands, Typha latifolia and T. angustifolia were observed as dominant species, and Nymphea tetragona as the sub-dominant species in the study area. An analysis of land use and water quality factors indicated that forest area played a considerable role in reducing the concentration of nutrients, and can act as a sink for surface/subsurface nutrient inputs flowing into wetland water, anchor the soil, and lower erosion rates into wetlands.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.44-53
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• 2008

To recognize the spatial and temporal variability of water temperature and dissolved oxygen in the Youngsan reservoir formed after dike construction, water temperature and dissolved oxygen data have been observed and analyzed from April, 2002 until March, 2003. As the results, certain stratifications were not distinctly observed in the Youngsan reservoir during summer, which was estimated due to the drainage characteristic from the Youngsan water gates. The yearly variation of water temperature in the Youngsan reservoir is shown seasonally ups and downs by the heat exchange between the atmosphere and the reservoir. On the other hand, dissolved oxygen and water temperature in the Youngsan reservoir have been shown inversed proportional correlation. As the calculation results of residence time and water exchange rate, it is considered that the feature of oxygen distribution is determined by the drainage characteristics caused the shortest residence time during summer, which also disturbed the formation of stratification in the Youngsan reservoir.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.640-646
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• 2011

Dissolved oxygen (DO) refers to the volume of oxygen that is contained in water, and is a major indicator of water quality. The objective of this paper was to investigate the effect of salinity on the dissolved oxygen characteristics in an ejector-aerator. An experimental aeration system composed of a motor-pump, an ejector, a motor-blower, a set of aeration and recirculation tank and a control panel. The dissolved oxygen concentrations decreased with the water salinity. The volumetric mass transfer coefficient increased with increasing the water salinity.

• Advances in environmental research
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• v.2 no.1
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• pp.1-8
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• 2013

There is a significant demand to make various dissolved gases in water. However, the conventional aeration method shows low gas mass transfer rate and gas utilization efficiency. In this study, a novel rotating wheel entraining gas method was developed for making high dissolved $O_2$ and $O_3$ in water. It produced higher concentration and higher transfer rate of dissolved $O_2$ and $O_3$ than conventional bubble aeration method, especially almost 100% of gas transfer efficiency was achieved for $O_3$ in enclosed reactor. For application of rotating wheel entraining gas method, aerobic bio-reactor and membrane bio-reactor (MBR) were successfully used for treatment of domestic and pharmaceutical wastewater, respectively; and vacuum ultraviolet $(VUV)/UV+O_3/O_2$ reactors were well used for sterilization in air/water, removal of dust particles and toxic gases in air, and degradation of pesticide residue and sterilization on fruits and vegetables.

• The Korean Journal of Food And Nutrition
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• v.34 no.6
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• pp.561-567
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• 2021

Curcumin is not soluble in water. Therefore, curcumin emulsion that can dissolve well in water were prepared using multi-emulsification technology, and the antioxidant activities and physical properties of emulsion were measured. Although curcumin was not dissolved in water, it was confirmed to be well dispersed in water when prepared in an aqueous dispersion curcumin emulsion. After dissolving curcumin using water and ethanol as solvents, respectively, the DPPH and ABTS radical scavenging abilities of the filtrate and the curcumin emulsion were measured. Because it was not dissolved in water, activities were not shown. However, when curcumin was dissolved in ethanol, the activities increased as the concentration of curcumin increased. On the other hand, when the curcumin emulsion was dissolved in water, it was found to have abilities. The curcumin emulsion was nano-homogenized and the size and distribution of the emulsified spheres were measured. It was confirmed to be nano-sized as it appeared as 9.083 nm/100%. In the results of the DPPH radical and ABTS radical scavenging abilities of curcumin nano-emulsion, it was confirmed that there was no change in the antioxidant abilities. In conclusion, water-dispersible curcumin prepared using multi-emulsification technology, and it was confirmed to exhibit antioxidant activity and emulsion stability.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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• pp.91-100
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• 1999

Treatment conditions of DAF(Dissolved Air Flotation) and removal rates of VOCs(Volatile Organic Compounds) in mixed water of H raw water and VOCs were investigated. The used VOCs were benzene, toluene, ethylbenzene, and xylene in aromatic compounds and iso propyl mereaptan, n-butyl mereaptan, dimethyl disulfide, and iso butyl mercaptan in odors. The related parameters include water type, treatment method, clay concentration, pH condition, flocculation time, flotation time, per-cent recycle, water temperature, pressure. The removal rates of VOCs were different on treatment process and water condition. Treatment time was longer, removal rates of VOCs was higher. Water temperature was more important than pressure in DAF parameters. Molecular weight was related with removal rate in several kinds of VOCs were decraesed by competition of each component in II raw water. When algac blooming D water was treated by DAF, TCOD(Total chemical Oxygen Demand) and chorophyll a was removed over 96%.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.303-309
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• 2006

Yongdam reservoir located in Jeoliabuk-do has had a lot of concerns for its algal blooming since it has started to fill water. Many water utilities near Yongdam area use reservoirs even though they have some problems with certain algae that cause tastes and odors and clog filters. In this research, dissolved air flotation (DAF) technology was examined for feasibility for removal of algae. OAF can save the capital cost for its compactness, because its hydraulic loadings (overflow rates) are 10 times higher than sedimentation, and hydraulic detention times are much shorter, typically 5 to 15 minutes. As a result of this research, PAC is effective rather than Alum to DAF for pretreatment. Higher DOC plays an important role to change zetapotential negatively to inhibit destabilization of particle to coagulation. The length of pipeline to carry pressurized water into reactor does not affect reaction.