• YAKHAK HOEJI
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• v.39 no.5
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• pp.495-505
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• 1995

The O/W microemulsion systems were made from 2 or 4% (w/w) oil (soybean oil, olive oil or isopropyl myristate) and 10, 15 or 20% (w/w) Brij 96. They were compared with micellar solution of equivalent surfactant concentration m therms of physicochemical properties, and the solubilization of sudan IV. They were characterized by dynamic light scattering, stability, surface tension, viscosity and rheogram. The mean diameters of O/W microemulsion systems were 10-15nm, and those of Brij 96 micellar solutions were 18-19 nm. Both of them were monodisperse systems. The O/W microemulsion systems showed Newtonian flow and their apparent viscosities were lower than those of micellar solutions. The surface tensions of O/W microemulsion systems were increased or decreased depending on the types of oil used, when compared with those of micellar solutions. The O/W microemulsion systems were very stable, and did not show any flocculation or aggregation. Their mean diameters were not changed after three months. But oxidation was observed in microemulsions without nitrogen gas at high temperature. There was a significant improvement in the sudan IV solubffimtion in micromulsion compared with that m the micellar solution containing equivalent concentration of surfactant. The size distribution and mean diameters of O/W micromulsions were not changed when sudan IV was solubilized.

• Journal of Environmental Science International
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• v.28 no.11
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• pp.927-933
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• 2019

A lipid-enriched strain of Botryococcus braunii (UTEX 572) was cultivated in a semi-batch aeration tank to enhance biomass as well as to develop intracellular lipids and fatty acids. A 30 day period of incubation produced 1.39 g/L of biomass and 0.31 g/L of total lipids in the biomass. The grown biomass was pre-treated using several methods to extract the total lipid content efficiently: ultrasonication was found to yield the highest percentage of lipids-namely 19.8% per biomass. Direct heating of biomass in an autoclave also showed better performance than when using only conventional solvent extraction. To enhance the biomass harvest and lipid extraction efficiency, coagulation and flocculation steps were added to the extraction process. It is noteworthy that not only the solvent type but also the solvent/biomass ratio greatly affected efficiency. In addition, the moisture content of the harvested(wet) biomass affected the efficiency significantly. This study elucidated the need for future research on optimizing this extraction process.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.249-249
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• 2019

하천에서 하상과의 접촉 없이 부유 상태로 이동하는 유사는 부유사로 정의된다. 부유사의 이동은 유사 입자의 침강 속도와 난류의 섭동 성분에 따라 결정된다. 실제 하천에서 부유사는 단일 크기가 아닌 여러 크기의 유사 입자가 혼재된 상태로 존재하는데, 유사의 이동을 보다 정확히 이해하기 위해서는 침강 속도를 결정하는 유사 입자 크기의 분포에 대한 이해가 요구된다. 진흙과 같은 점착성 유사의 경우에는 모래와 같은 비점착성 유사와는 달리 입도 분포를 구성하는 유사 입자의 크기가 끊임없이 변화한다. 이러한 유사의 특성 변화는 유사 알갱이 표면의 전자기적 점착력으로 인한 응집 현상(Flocculation Process)에서 기인한다. 응집 현상으로 인해 점착성 유사는 물과 유사 입자의 덩어리인 플럭(Floc)을 형성하며, 플럭의 특성은 지속적으로 변화한다. 따라서 점착성 유사의 이동을 이해하기 위해서는 흐름 특성 및 입도 분포뿐만 아니라 플럭의 응집 현상에 관한 이해가 함께 이루어져야함을 알 수 있다. 본 연구에서는 플럭의 응집 현상으로 인한 크기 변화와 입도 분포를 이해하기 위한 모형 개발의 방법론을 제시하고자 한다. 입도 분포 모형의 개발을 위해 추계학적 접근법이 이용되며, 추계학적 접근법을 이용하여 수치 실험을 수행하기 위해 몬테-카를로 방법이 적용되었다. 입도 분포 모형과 유사 이동 모형의 결합을 통해 흐름 내 부유 상태로 이동하는 점착성 유사 입도 분포에 관한 수치 모형 개발이 가능하다.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.543-551
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• 2019

In China, serious environmental problems are induced by the extremely soft construction waste slurries in many urban areas, and there is no appropriate method to treat it presently. In this paper, four model tests were conducted to investigate the efficiency of waste slurry treatment by combining three conditioning agents which can change characteristics of the slurries with a traditional vacuum preloading method. The tests of size analysis of particle aggregate were conducted to investigate the influence of different conditioning agents on the size distributions of particle aggregate. During the model test, the discharged water volumes were monitored. The pore-size distribution and void ratio of the waste slurries after the vacuum preloading were measured by mercury intrusion porosimetry (MIP). It is found that 1) During the natural precipitation, volume of water out of the organic agent is higher than that of the mixed agent, but it is smaller than that of the mixed agent in the vacuum preloading stage; 2) the mixed agent has a higher total volume of water out than the organic agent and the inorganic agent after test, while the organic agent and the inorganic agent have little difference with respect to the drainage effect. The results demonstrate that the combination of mixed conditioning agent and vacuum preloading for the solid-liquid separation in waste slurry has a satisfactory effect and can be applied in engineering practice.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.386-391
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• 2021

The formation of CaCO₃ in microalgal culture is investigated and applied for effective separation of microalgae. The presence of several cationic ions in the culture medium mediates the formation of 3 types of mineral precipitates depending on the concentration of mineral precursors, Ca²⁺ and CO₃^2-, amorphous nano-flakes, rhombohedral calcites, and spherical vaterites. While amorphous phased precipitates are formed for all concentrations of mineral precursor, only calcites are formed for 30 mM solutions of mineral precursor, and mixtures of calcites and vaterites are formed for 50 and 100 mM solutions of mineral precursor. The harvesting efficiency is also dependent on the concentration of the mineral precursor: from 90 % for 10 mM to 99 % for 100 mM after 60 mins' of gravitational sedimentation. The formation of nano-flakes on the surface of microalgal cells induces the flocculation of microalgae by breaking the stable dispersion. The negatively charged surface of the microalgal cell is compatible not only with nano-flake attachment but also with the growth of calcitic crystals in which microalgal cells are embedded.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.153-162
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• 2021

The effects of activated carbon originated Ballasted Flocculant (BF) on the settleability of activated sludge and the recovery of BF by Hydro-cyclone (HC) were analyzed experimentally. Two kinds of BF (M-I: 125-250 ㎛, M-II: 250-425 ㎛ in dia.) and three kinds of activated sludges with different SS concentration (2,300-7,100 mg/L) were applied for this study. With the dosage variation of BF from 0.14 to 1.3 g-BF/g-SS, we could obtain 24-31% improvement in SV30 (Sludge Volume after 30min sedimentation) for the lowest SS concentration sludge (2,300 mg/L). Whereas the SV30 improvement was much higher as 44-48% for the highest SS concentration sludge (7,100 mg/L). The settling characteristics of the sludge with BF followed Vesilind model the best among three models (Vesilind, Takacs and Cho model). HC could effectively separate BF with the separation efficiency of 70-90% and over 95% separation efficiency could be obtained when the HC was applied twice.

• Journal of Korean Society on Water Environment
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• v.39 no.3
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• pp.223-230
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• 2023

Harmful algae blooms have become a serious environmental problem in major river basins in Korea. They are known to produce various algal organic matters (AOMs) including intracellular organic matters (IOMs) and extracellular organic matters (EOMs). Generally AOMs cannot be easily removed by coagulation/flocculation process in conventional drinking water plants. AOMs produced by blue-green algae also include various toxins such as Microcystins, Anatoxin-a, and Saxitoxin known to have harmful effects on living organisms in aquatic environment. In this study, toxic effects of EOMs produced by three different algae species (Microcystis sp., Anabaena sp., and Oscillatoria sp.) on zebrafish were investigated using electroencephalography (EEG) recording method, a technology for recording brain activity. Electroencephalographic changes in zebrafish revealed that a low EOM had a negative effect on zebrafish compared to both Anabaena sp. and Oscillatoria sp. at 30 ppm EOM exposures. This result might be due to Microcystins present in EOMs produced by Microcystis sp. As a result of power spectrum density anallysis, exposure to EOMs produced by Microcystis sp. caused a state of vigilance in zebrafish. This EEG based toxicity test can be used to examine effects of harmful materials at low levels on living organisms in an aquatic system.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.121-131
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• 2023

Clay sedimentation has been widely analyzed for its application in a variety of geotechnical constructions such as mine tailing, artificial islands, dredging, and reclamation. Chemical flocculants such as aluminum sulfate (Al₂(SO₄)₃), ferric chloride (FeCl₃), and ferric sulfate (Fe(SO₄)₃), have been adopted to accelerate the settling behaviors of clays. As an alternative clay flocculant with natural origin, this study investigated the settling of xanthan gum-treated kaolinite suspension in deionized water. The sedimentation of kaolinite in solutions of xanthan gum biopolymer (0%, 0.1%, 0.5%, 1.0%, and 2.0% in a clay mass) was measured until the sediment height was stabilized. Kaolinite was aggregated by xanthan gum via a direct electrical interaction between the negatively charged xanthan gum molecules and positively charged edge surface and via hydrogen bonding with kaolinite particles. The results revealed that the xanthan gum initially bound kaolinite aggregates, thereby forming larger floc sizes. Owing to their greater floc size, the aggregated kaolinite flocs induced by xanthan gum settled faster than the untreated kaolinite. Additionally, X-ray computed tomography images collected at various depths from the bottom demonstrated that the xanthan gum-induced aggregation resulted in denser sediment deposition. The findings of this study could inspire further efforts to accelerate the settling of kaolinite clays by adding xanthan gum.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.77-83
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• 2023

As a result of algal bloom, algal organic matters (AOMs) are rapidly increased in surface water. AOMs can act as precursors for the formation of harmful disinfection by-products (DBPs), which are serious problems in water treatment and human health. The main aim of this study is to characterize the formation of DBPs from AOMs produced by three different algae such as Oscillatoria sp., Anabaena sp., and Microcystis aeruginosa under different algal growth phases. In an effort to examine formation of DBPs during chlorination, chloroform (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were determined under various CT (product of disinfectant concentration and contact time, mg·min/L) values. Generally, the amounts of DBPs tended to increase with increasing CT values at the most growth phases. However, there was a significant difference between the amounts of DBPs produced by the three algal species at different growth phases. This result is likely due to the chemical composition variability of AOM from different algae at different growth phases. In addition, the effect of pre-ozonation on coagulation for the removal of AOMs from three algal species was investigated. The pre-ozonation had a positive effect on the coagulation/flocculation of AOMs.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.307-307
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• 2020

하천에서 하상과의 접촉 없이 부유 상태로 이동하는 유사는 부유사로 정의된다. 부유사의 이동은 유사 입자의 침강 속도와 난류의 섭동 성분에 따라 결정된다. 실제 하천에서 부유사는 단일 크기가 아닌 여러 크기의 유사 입자가 혼재된 상태로 존재하는데, 유사의 이동을 보다 정확히 이해하기 위해서는 침강 속도를 결정하는 유사 입자 크기의 분포에 대한 이해가 요구된다. 진흙과 같은 점착성 유사의 경우에는 모래와 같은 비점착성 유사와는 달리 입도 분포를 구성하는 유사 입자의 크기가 끊임없이 변화한다. 이러한 유사의 특성 변화는 유사 알갱이 표면의 전자기적 점착력으로 인한 응집 현상(Flocculation Process)에서 기인한다. 응집 현상으로 인해 점착성 유사는 물과 유사 입자의 덩어리인 플럭(Floc)을 형성하며, 플럭의 특성은 지속적으로 변화한다. 따라서 점착성 유사의 이동을 이해하기 위해서는 흐름 특성 및 입도 분포뿐만 아니라 플럭의 응집 현상에 관한 이해가 함께 이루어져야함을 알 수 있다. 본 연구에서는 플럭의 응집 현상으로 인한 크기 변화와 입도 분포를 이해하기 위한 모형 개발의 방법론을 제시하고자 한다. 입도 분포 모형의 개발을 위해 추계학적 접근법이 이용되며, 추계학적 접근법을 이용하여 수치 실험을 수행하기 위해 몬테-카를로 방법이 적용되었다. 입도 분포 모형과 유사 이동 모형의 결합을 통해 흐름 내 부유 상태로 이동하는 점착성 유사 입도 분포에 관한 수치 모형 개발이 가능하다.