• Journal of Environmental Science International
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• v.19 no.1
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• pp.89-96
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• 2010

The separation of $TiO_2$ wastewater carried out by an electrocoagulation/flotation process, which had various operating parameters. The effect of electrode material (aluminum and four dimensionally stable electrode), applied current (0.07~0.5 A), electrolyte concentration (0~1 g/L), solution pH (3~11), initial turbidity (1000~20000 NTU) and suspended solid concentration (5000~25000 mg/L) were evaluated. Turbidity removal efficiency of the soluble anode (aluminum), which could produce metal ions, was higher than that of the dimensionally stable electrode. Considering operation time, turbidity removal and electric power, optimum current was 0.19 A. The more NaCl dosage was high, the less electric power was required. However, optimum NaCl concentration was 0.125 g/L considered removal efficiency, operation time and cost. Initial $TiO_2$ concentration did not affected turbidity removal on the electrocoagulation/flotation operation. The electrocoagulation/flotation process was proved to be a very effective separation method in the removal of $TiO_2$ from wastewater.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.491-499
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• 2009

The removal of turbidity from $TiO_2$ wastewater by an electrocoagulation/flotation process was studied in a batch reactor. The response surface methodology (RSM) was applied to evaluate the simple and combined effects of the three main independent parameters, current, NaCl dosage and initial pH of the $TiO_2$ solution on the turbidity removal efficiency, and to optimize the operating conditions of the treatment process. The reaction of electrocoagulation/flotation was modeled by use of the Box-Behnken method, which was used for the fitting of a 2nd order response surface model. The application of RSM yielded the following regression equation, which is an empirical relationship between the turbidity removal efficiency of $TiO_2$ wastewater and test variables in uncoded unit: Turbidity removal (%)=69.76+59.76Current+11.98NaCl+4.67pH+5.00Current${\times}$pH-160.11$Current^2-0.34pH^2$. The optimum current, NaCl dosage and pH of the $TiO_2$ solution to reach maximum removal rates were found to be 0.186 A, 0.161 g/l and 7.599, respectively. This study clearly showed that response surface methodology was one of the most suitable method to optimize the operating conditions for maximizing the turbidity removal. Graphical response surface and contour plots were used to locate the optimum point.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.269-272
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• 2002

Turbidity currents, often develop after heavy storm events, deliver various non-point pollutants and tend to lead eutrophication, depressed dissolved oxygen, and sedimentation in reservoirs. Field observations were performed to investigate the flow regimes of turbidity currents and their impact on reservoir water quality in Daecheong Reservoir. A 2D laterally-averaged hydrodynamic and water quality model was applied to simulate the temporal and spatial distributions of turbidity in the reservoir, and evaluated by comparing with the field data.

• Journal of Korea Water Resources Association
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• v.50 no.3
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• pp.201-210
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• 2017

This study proposes a numerical model which is able to simulate turbidity currents intruding into a reservoir and resulting sediment depositions. The proposed model is applied to laboratory experiments by Toniolo and Schultz (2005), and propagation of turbidity currents, morphological change, and trap of suspended sediment are simulated. It is simulated that the turbidity current after plunging at the foreset of the model delta, propagates along the bottom. The thickness of the turbidity current increases significantly after being blocked by the dam, and this effect is propagated in the upstream direction. In addition, it is simulated that the foreset moves in the downstream direction due to both the bedload and suspended load and the thickness of the bottom set increases due to the suspended load. It is found that the height of the intake affects the thickness of the turbidity current and the location of the internal hydraulic jump. The impact of the height of the intake on the trap efficiency is not clear in the experimental results, however, overall trap efficiency is predicted quite successfully by the model. Also, sensitivity analysis is carried out, and the results indicates that the particle size affects the trap efficiency most.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.3
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• pp.1-9
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• 1999

This paper described the results of the characteristics of the near-bottom flow and field analysis of the tidal flats sediment. It was the aim of this paper to grasp current flow of tidal flat's environment and influence factor for environmental change forecast of tidal flats. Field measurement of water velocity, water elevation, bed materials test, and temperature distribution of tidal flat were conducted. Thereafter, current flow, turbidity and temperature distribution of tidal flat sediment have been discussed. The field research results showed that the fluctuating velocity near the seabed before and after its appearance at low tide was strongly affected by the wind wave. The resuspension of the sea-bottom sediment took place with great intensity before and after the appearance of the seabed at low tide. Both the sea water level and the weather condition were a significant influential factors. Such as, temperature and turbidity just on the surface and the shallow layer of seabed sediments were varied largely with time and weather conditions, but that its deeper layers was almost constant. Temperature on the seabed sediments was strongly influenced by irradiance and water depth. The temperature variation of the tidal flat and the variation characteristics of the current flow and turbidity depend greatly on the inhabiting environment of the tidal flat benthic organism.

• 한국해양학회지
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• v.22 no.2
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• pp.105-118
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• 1987

A series of anchor stations were occupied along the Keum EAstuary during six different periods of tidal and fluvial regimes. The results clearly show that the formation and evolution of the turbidity maximum play an important role in the sedimentary processes in this environment. The turbidity maximum in the Keum Estuary is primarily related to the tidal range at the mouth and is caused by the resuspension of bottom sediments. In this estuary, the turbidity maximum is not a permanent feature and shows semidiurnal, fortnightly and seasonal variations. Repetition of deposition and resuspension of fine sediments occur in response to the variation in current velocity associated with semidiurnal tidal cycles. The core of turbidity maximum shifts landward or seaward accordion to the flood-ebb succession. The turbidity maximum also shows a fortnightly variation in response to the spring-neap cycles. Thus, the turbidity maximum degenerates during neap-tide and regenerates during spring-tide. The freshwater discharge is also an important factor in the formation and destruction of the turbidity maximum. The increase in freshwater discharge in rainy season can create an ebb-dominant current pattern which enhances the seaward transport of suspended sediments, resulting in the shortening of residence time of suspended materials in the estuary. Thus, under this high discharge condition, the turbidity maximum exists only during spring-tide and starts to disappear as the tidal amplitude decreases.

• Journal of Environmental Science International
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• v.26 no.5
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• pp.563-572
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• 2017

The Electrocoagulation-Flotation (ECF) process has great potential in wastewater treatment. ECF technology is effective in the removal of colloidal particles, oil-water emulsion, organic pollutants such as microalgae, and heavy metals. Numerous studies have been conducted on ECF; however, many of them used a conventional plate-type aluminum anode. In this study, we determined the effect of changing operational parameters such as power supply time, applied current, NaCl concentration, and pH on the turbidity removal efficiency of kaoline. We also determined the effects of different electrolyte types (NaCl, $MgSO_4$, $CaCl_2$, $Na_2SO_4$, and tap water), as well as the differences caused by using a plate-type and mesh-type aluminum anode, on the turbidity removal efficiency. The results showed that the optimal values of ECF time, applied current, NaCl concentration, and pH were 5 min, 0.35 A, 0.4 g/L NaCl in distilled water, and pH 7, respectively. The results also revealed that the turbidity removal efficiency of kaoline in different electrolytes decreased in the following sequence, given the same conductivity: tap water > $CaCl_2$ > $MgSO_4$ > NaCl > $Na_2SO_4$. The turbidity removal efficiency of the mesh-type aluminum anode was significantly greater than the plate-type aluminum anode.

• Environmental Engineering Research
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• v.18 no.3
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• pp.157-161
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• 2013

Treatment of textile wastewater by the electrocoagulation (EC) process is being investigated by this experimental study. The objective of this experiment is to observe the efficiency of the EC process in removing chemical oxygen demand (COD) and turbidity. In this experiment an iron electrode is used in the EC process, and different working parameters such as pH, current density and operating time were studied in an attempt to achieve a higher removal capacity. The results show that the maximum COD removal occurred at neutral pH at operating time 30 min. COD and turbidity removal reaches at maximum, with optimum consumption of electrodes, between current density 85-95 $A/m^2$, and only trace amounts of metals were determined in the EC treated effluent.

• Korean Journal of Community Nutrition
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• v.17 no.2
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• pp.205-214
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• 2012

This study examined intakes of nutrients, carotenoids and polyphenols according to lens turbidity levels among adults visiting a cataract clinic. A total of 102 males and females aged 40 years or higher agreed to participate in the study, and a face-to-face survey interview was conducted to obtain information on general characteristics, health behaviors, and dietary intakes of each participant. The dietary data were collected by a food frequency questionnaire which was previously validated in a Korean population. In addition to essential nutrients, intakes of a total of 10 carotenoids and polyphenols were calculated based on the tables of food functional composition developed by National Academy of Agricultural Science. The subjects were divided into 3 groups according to turbidity levels (< 16, ${\geq}16$ and < 25, ${\leq}25$), and health behaviors and dietary intakes were compared among the turbidity groups. Data showed seemingly higher energy intake and lower dietary antioxidant (i.e., vitamin A, ${\beta}$-carotene, lutein, zeazanthin, lycopene, cryptozanthin) intakes in the highest turbidity group. However, no statistically significant findings were found in all the comparative analysis on characteristics of health behavior and intakes of nutrients, carotenoids and polyphenols. The current study findings should be cautiously interpreted in consideration of several limitations including a cross-sectional study design, a small sample size, uneven sample size distribution across turbidity groups, and limited generalizability due to using a convenience sample. Therefore we cannot conclude that the risk of cataract is unrelated with dietary antioxidant intakes based solely on the results of this study.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05b
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• pp.877-882
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• 2001