• Journal of environmental and Sanitary engineering
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• v.19 no.3 s.53
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• pp.58-64
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• 2004

Biological treatment of wastewater was studied with a purpose to remove TOC by the reduction of water hardness. The optimal conditions of coagulant were determined by reaction time and amount of coagulant. Experimental results indicate that the biological treatment after physico-chemical treatment was found to provide very efficient removal efficiency in the process to treat the textile wastewater, including the carbon dioxide treatment. The combined process of carbonization in the physico-chemical treatment respectively was increased the removal efficiencies of $30.0\%$ in biological treatment in comparison with exclusive biological treatment. As a result, the treatment of hardness after carbonization had the best removal efficiency of approximately $60.0\%$. The removal efficiencies in the exclusive biological treatment using Bacillus subtilis and after carbonization were increased by $38.9\%\;and\;69.0\%$ respectively. The combined Bacillus subtilis-assisted biological treatment was determined to be the most effective method to treat the textile wastewater in an economic point of view, the water quality in the wastewater treatment plays an important role.

• KSTLE International Journal
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• v.5 no.1
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• pp.32-35
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• 2004

The purpose of this study is to investigate the effects of the structure and mechanical properties of laser-processed pads on their polishing behavior such as their removal rate and WIWNU (within wafer non-uniformity) during the chemical mechanical planarization (CMP) process. The holes on the pad acted as the reservoir of slurry particles and enhanced the removal rate. Without grooves, no effective removal of wafers was possible. When the length of the circular-type grooves was increased, higher removal rates and lower wafer non-uniformity were measured. The removal rate and non-uniformity linearly increased as the elastic modulus of the top pad increased. Higher removal rates and lower non-uniformity were measured as the hardness of the pad increased.

• Fashion & Textile Research Journal
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• v.14 no.3
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• pp.492-500
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• 2012

Cocoa is a popular drink for children and contains healthy polyphenols however; a deep brown stain is left when cocoa is spilled over clothes. The main pigments in cocoa are anthocyanins that change in washing solutions with different alkalinity and metals. The removal and color changes in a cocoa stain after washing with various pH solutions and water hardness were studied. Alkalinity and the water hardness of washing solutions were important factors for the removal of cocoa stains. The removal of cocoa things in washing solutions without detergent was low (and even became negative after removal and darker) in solutions with a pH 9 and above. The cocoa stain was not removed and only the fabric color faded, although the cocoa stained cloth was washed with Korea tap water that has a pH of 7. The cocoa stain removal in detergent solutions was conspicuously higher than for only water. Even in detergent solutions, the cocoa stain removal decreased as water hardness increased. Cocoa stain removal was more effective and the color dimmest when the stained cloth was washed in a solution without the metal cations, and the bleach added with the detergent at a temperature of $40^{\circ}C$ and for longer than 20 minutes. Effective and economical equipment for tap water softening for a washing machine should be developed and used to improve cocoa stain removal.

• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.12-16
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• 2020

Circulating cooling systems consume a lot of water, and most of the water from river, which contains a large amount of Ca2+, Mg2+, et al, and has the characteristics of high hardness and large turbidity. The water can form scale on the surface of the heat exchanger and the pipes, which would reduce the heat transfer efficiency and affect the heat exchanger's length of service. In this study, the Superconducting High Gradient Magnetic Separation (S-HGMS) technology was used in river water treatment and the effects of agent A, agent B, and S-HGMS on the removal of hardness and turbidity were discussed. The results showed that the hardness removal rate reached 71.3% and the turbidity was decreased to 0.5 NTU.

• Journal of Periodontal and Implant Science
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• v.32 no.2
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• pp.315-324
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• 2002

The purpose of this in vitro study was to evaluate the efficiency of Er:YAG laser on calculus removal and the morphologic changes and hardness of the irradiated surface at different power settings. This experiment used human teeth which were extracted due to periodontal disease and had a band of calculus. Forty root slabs ($5{\times}5mm$) were made and divided into control group and irradiated groups. Experimental groups were as follows; Control group (root planing), Group1 (irradiated with laser at 30mJ), Group2 (irradiated with laser at 60mJ), Group3 (irradiated with laser at 100mJ). Twelve root slab embedded in resin block were used in each group. Er:YAG laser was applied under water irrigation with the tip held perpendicular to the root surface in contact mode. The treatment time was measured until the calculus was removed completely under naked eyes. The efficiency of calculus removal was evaluated by the time for removal. Morphological changes of laser irradiated site were observed under SEM and the surface hardness was measured using a VH tester. The results were as follows; 1. The efficiency of laser scaling was increased with increasing the energy level of irradiation(p<0.05). 2. The morphological changes such as carbonization, crater and scale-like defects in the irradiated root surface were frequently observed with increasing the energy level. 3. The surface hardness tended to increase at 60mJ and 100mJ irradiated groups than that of control group. From the results evaluting on the efficiency, morphological change and surface hardness, lower energy level was suggested for the clinical application of the Er:YAG laser in scaling.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.40-44
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• 2004

To the removal of hardness materials, we've test the absorptive capacity of main material $Mg^{2+},\;Ca^{2+}$ on the using the activated carbon powder saturated in 0.1M Nitrilotriacetic acid by experimental methods. The absorptive properties of $Ca^{2+}\;and\;Mg^{2+}$ were measured with absorbent quantity and contact time., and investigated the physical properties of overall rate constant and adsorption constant adsorption isotherm, and Langmuir and Freundlich constant. In case of k' adsorption rate constants of $Ca^{2+},\;Mg^{2+}$, was 0.00299, 0.00529 by Bhattahary and Venkobachar equation. $k_{aa}$ was 0.00373, 0.00640 according with adsorption rate constants of Lagergren.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.2
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• pp.68-74
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• 2004

A blast furnace slag(BFS) has been used as a filter medium for the treatment of domestic waste waters during the period of 9-month. More than 90% of phosphorus was removed while the hardness of the treated water increased by 5 times and the pH was significantly raised from 6.8 to 10.8. The high hardness and pH of the treated water indicated dissolution of BSF by the sewage. The experimental results suggest that BFS could be utilized for the removal of phosphorus in the waste water treatment plant using aquatic plants and gravels.

• Korean journal of food and cookery science
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• v.30 no.3
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• pp.351-359
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• 2014

The application of persimmon for making new products was investigated by analyzing the degree of astringency removal, softness of fruit, and sensory properties of Daebong persimmons (Diospyros kaki L) treated with three different astringency removal methods of steeping in water, steeping in 1% salt solution, and vacuum packing at $40^{\circ}C$. The weight of persimmon fruit increased with increasing steeping time, but decreased with increasing vacuum packing time. The fruit steeped in $40^{\circ}C$ salt solution (1%, w/w) was not detected with soluble tannin and not developed color with ferric chloride after steeping for 9 h. A total of 12 h of steeping time was required for removing soluble tannin using other methods. The lightness (L) in color and hardness in texture decreased when storage time increased, regardless of astringency removal methods. In overall, the preference was shown with the highest score in persimmon steeped in salt solution for 9 h and 12 h that were vacuum packed at $40^{\circ}C$. In conclusion, the astringency removal condition of Daebong persimmon was good after being steeped on 1% salt solution for 9 h at $40^{\circ}C$.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.2
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• pp.15-24
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• 1999

A new technique for recycling of white water was developed in order to reduce the calcium hardness in a closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by reacting with sodium carbonate, and the precipitated $CaCO_3$ was removed from the system using a flotation fractionation method, which has been commonly used in deinking process. In the flotation stage, a mixed gas of $CO_2$-air was purged into the flotation cell because the pH of $Na_2CO_3$-treated white water was reduced to neutral by $CO_2$ gas. Since $CaCO_3$ precipitate tends to stick onto fine fiber surface and then selectively removed from the white water, a proper amount of suspended solid in white water acts as an important factor for deciding the removal efficiency. By the application of $Na_2CO_3$ addition-$CO_2$ flotation to the short circulated white water, the calcium hardness was significantly reduced by 87% and more. Removal of calcium ions with fine fibers led to a drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.164-171
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• 1999

A new technique for recycling process water was developed in order to reduce the calcium hardness of the closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by a reaction with sodium carbonate and the CaCO$_3$precipitates were easily removed from the system by a dissolved air flotation(DAF) method. After the DAF stage, CO$_2$-gas was purged into the water because the pH of Na$_2$CO$_3$-treated white water was reduced to neutral by CO$_2$gas. Since CaCO$_3$precipitate tends to stick onto the fine fiber surface and then is selectively removed from the water, a proper amount of suspended solid in the process water acts as an important factor in deciding the removal efficiency. By the application of Na$_2$CO$_3$addition - DAF - CO$_2$purging to the short circulated white water the calcium hardness was significantly reduced by 92% and more. The removal of calcium ions with fine fibers led to drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.