• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.93-98
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• 2001

Wastewaters produced in textile industrial processes contain dyes which are not easily amenable to biological treatment. The object of this study is to determine the post-treatment system of biological process for the textile wastewater by comparing three different types of chemical process, which were 1) post-treatment by ozone or UV, 2) post-treatment by coagulation,3) post-treatment by ozone or UV followed by coagulation. In an application ozone or UV as a post-treatment, color was generally decreased with time, however, SCOD removal effect was not that good. When coagulation was used as point-treatment process, the effluent quality was satisfying. Therefore, the application of coagulation process as a post-treatment of biological process would be more desirable than that as a ozone or UV.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.30 no.2
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• pp.8-14
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• 2007

The powder blasting process has become an important machining technique for the cost effective fabrication of micro devices. This process is similar to sand blasting, and effectively removes hard and brittle materials. A large number of investigations on the abrasive jet machining with such output parameters as material removal rate, penetration and surface roughness have been carried out and reported by various authors. To achieve higher surface roughness, to increase material removal rate and to identify the influence of blasting parameters on the output parameters, we use the taguchi method which is one of the design methods of experiments. We can select process parameters to optimize the blasting process of glass. Experimental results indicate that the taguchi method is useful as a robust design methodology for the powder blasting process.

• Progress in Superconductivity and Cryogenics
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• v.21 no.2
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• pp.15-21
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• 2019

In the mine exploration sites, sustainable treatment system of mine water with energy saving and minimized chemical additives is required. Since most of the mine water contains highly-concentrated ferrous ion, it is necessary to study on the removal method of iron ions. We propose the system consisting of two processes; precipitation process by air oxidation using solid catalyst-modified magnetite and separation process combining gravitational sedimentation and magnetic separation using a permanent magnet. Firstly, in the precipitation process (a former process of the system), we succeeded to prepare solid catalyst-modified magnetite. Air oxidation using solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material showed high iron removal capability. Secondly, in the separation process (latter process of the system), solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material can be separated by a superconducting bulk magnet and a permanent magnet.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.E2
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• pp.41-48
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• 2005

A novel hybrid system composed of a biotrickling filter and an activated sludge reactor was investigated under the conditions of four different SRTs (sludge retention times). The performance of the hybrid reactor was found to be directly comparable among the four different sludge ages. Discernible differences in the removal performance were observed among four different SRTs of 2, 4, 6, and 8 days. High removal efficiency was achieved by continuous circulation of activated sludge over the immobilized mixture culture, which allowed on pH control, addition of nutrients, and removal of paint VOCs (volatile organic compounds). The results also showed that the removal efficiency for a given pollutant depends on the activity of microorganisms based on the SRT. As the SRT increased gradually from 2 to 8 days, the average removal performance decreased. The highest removal rate was achieved at the SRT of 2 days at which the highest OUR (oxygen uptake rate), $6.1mg-O_2/liter-min$ was measured. Biological activity in the recycle microbes decreased to a much lower level, $3.6mg-O_2/liter-min$ at a SRT of 8 days. It is thus believed that young microorganisms were more active and more efficient for the VOCs removal of low concentrations and high flow rates. The apparent correlation of $R^2=0.996$ between the average removal efficiency and the average OUR at each SRTs suggests that VOCs degradation by young cells significantly affected the overall removal efficiency for the tested SRTs.

• Transactions on Electrical and Electronic Materials
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• v.2 no.3
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• pp.24-27
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• 2001

The end point of oxide chemical mechanical polishing (CMP) have determined by polishing time calculated from removal rate and target thickness of oxide. This study is about control of oxide removal amounts on the shallow trench isolation (STI) patterned wafers using removal rate and thickness of blanket (non-patterned) wafers. At first, it was investigated the removal properties of PETEOS blanket wafers, and then it was compared with the removal properties and the planarization (step height) as a function of polishing time of the specific STI patterned wafers. We found that there is a relationship between the oxide removal amounts of blanket and patterned wafers. We analyzed this relationship, and the post CMP thickness of patterned wafers could be controlled by removal rate and removal target thickness of blanket wafers. As the result of correlation analysis, we confirmed that there was the strong correlation between patterned and blanket wafer (correlation factor: 0.7109). So, we could confirm the repeatability as applying for STI CMP process from the obtained linear formula. As the result of repeatability test, the differences of calculated polishing time and actual polishing time was about 3.48 seconds. If this time is converted into the thickness, then it is from 104 $\AA$ to 167 $\AA$. It is possible to be ignored because process margin is about 1800 $\AA$.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.73-78
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• 2005

This study was performed to examine the disinfection capability of a Rotating Activated Bacillus Contactor (RABC) system, in which the predominant species, Bacillus sp. was expected to have a removal or inactivation effect of total coliforms. In a settling test with mixtures of E. coli and Bacillus sp., a high removal of E. coli was observed at $20{\sim}40^{\circ}C$, while insignificant removal at $10^{\circ}C$. In a batch test, a 4.5% addition of Bacillus sp. to activated sludge considerably enhanced the removal effect of total coliforms, indicating Bacillus sp. played an important role in improving the settlability of the sludge and coliforms. In a pilot scale RABC system, the concentration of total colifroms reduced remarkably in the settling tank, suggesting that total coliforms in the RABC process were eliminated through coagulation and precipitation, probably due to extracellular polymeric substance (EPS) of Bacillus sp. The fraction of Bacillus sp. in the total cell count in the RABC process was in the range of 4.5%~6.3%. The majority (75%) of the Bacillus sp. in the RABC process was Bacillus subtilis which is known to enhance coagulation and precipitation by producing EPS. Hence, an adoption of a RABC process might be able to eliminate the disinfection unit process from a wastewater treatment system.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.391-396
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• 2014

Ultrapure water (UPW) is water containing nothing but water molecule ($H_2O$). The use of UPW is increasing in many industries such as the thermal and nuclear power plants, petrochemical plants, and semiconductor manufacturers. In order to produce UPW, several unit processes such as ion exchange, reverse osmosis (RO), ultraviolet (UV) oxidation should be efficiently arranged. In particular, RO process should remove not only ions but also low molecular weight (LMW) organic matters in UPW production system. But, the LMW organic matter removal data of RO membranes provided by manufacturers does not seem to be reasonable because they tested the removal in high concentration conditions like 1,000 ppm of isopropyl alcohol (IPA, MW=60.1). In this study, bench-scale experiments were carried out using 4-inches RO modules. IPA was used as a model LMW organic matter with low concentration conditions less than 1 ppm as total organic carbon (TOC). As a result, the IPA removal data by manufacturers turned out to be trustable because the effect of feed concentration on the IPA removal was negligble while the IPA removal efficiency became higher at higher permeate flux.

• Journal of environmental and Sanitary engineering
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• v.17 no.4
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• pp.29-38
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• 2002

Advanced oxidation of wastewater was studied with a purpose to remove TOC and color by the ozone-assisted Fenton reaction. The optimal conditions were determined by hydrogen peroxide and ozone concentrations. Experimental results indicate that the ozone treatment after Fentons process was found to provide very efficient removal efficiency in the process, avoiding the exclusive ozone treatment. The combined process of ozone in the Fenton oxidation respectively was increased removal efficiences of 10.7％ in comparison with exclusive Fenton oxidation. Also, the treatments of ozone after Fenton's oxidation respectively had increased the removal efficiences of 16.％. As a result, the treatment of ozone after Fentons oxidation had the best removal efficiency of approximately 96％. Removal efficiency of color was significantly increased as mush as 26％ by the advanced Fenton's oxidation in comparison with exclusive Fenton's oxidation. The removal efficiencies in the biological treatment using Bacillus subtilis after Fenton's oxidation and after Fenton's and ozone's oxidation were increased by 14％ and 19％ respectively. Although these combined Bacillus subtilis-assisted Fenton's oxidation was determined to be effective method to treat the dyeing wastewater in an economic point of view, the choice of wastewater treatment can be varied depending on water quality.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.128-131
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• 2003

It is well known that the membrane separation process combined with surfactant micelle (micellar-enhanced ultrafiltration) or polyelectrolyte (polyelectrolyte-enhanced ultrafiltration) can remove heavy metals effectively. However, the environmental hazard of surfactant or polyelectrolyte remained in effluent is a serious disadvantage of these methods. In this study, humic substances (HS) were used as complexing agents for metal removal instead of synthetic chemicals. The HS are a sort of natural organic matters which are biodegradable and abundant in natural environment. And the functional groups such as carboxyl groups and phenols in HS can bind with the cationic radionuclides and form complexes. Therefore separation process using them will be more environmental-friendly. The effects of concentration of HS and pH on the removal of cobalt were investigated. The ultrafiltration process was applied to the separation of the cobalt - HS complexes from the aqueous stream. At the concentration of > 3 g/L of HS and pH of 6, over 95 % of cobalt was removed by regenerated cellulose membrane of molecular weight cut-off (MWCO) 3,000. As the concentration of HS increased, the removal of cobalt also was improved because of increase in biding sites (functional groups). The cobalt removal increased from 72.5 % to 97.5 % when pH increased from 4 to 8 at the concentration of 3 g/L HS because of increase in HS solubility and cobalt hydroxide precipitation. In the presence of NaCl, the removal efficiency of cobalt decreased.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.208-214
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• 2004

Dissolved air flotation (DAF) is an effective solid/liquid separation process for low density floc particles such as algal, color-alum and clay-alum flocs produced from low turbidity water. The removal of taste and odor-causing organics (2-mthylisoboneol and geosmin) originating from algae in drinking water is a local and worldwide concern. Although DAF has been effectively applied for the removal of suspended solid, its application for the treatment of dissolved organic carbon is very limited. In this study, a new hybrid system consisting of adsorption and DAF processes was introduced for the simultaneous removal of algae and taste and odor-causing organics. Powdered activated carbon (PAC) was used as an adsorbent. In this proposed system, the major concern of eliminating the spent PAC from the system was also addressed. It was found that zeta potential of algae and PAC was increased with coagulant dosage, and the removal efficiency in DAF was also enhanced up to 90~95% under the given experimental conditions. Based on this study, the hybrid process was found to be a promising technology for the simultaneous removal of algae and dissolved organic pollutants.