• Environmental Engineering Research
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• v.10 no.5
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• pp.213-226
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• 2005

To treat wastewater efficiently by a one-step process of nitrogen removal, a new bacterial strain producing $N_2$ gas from ${NH_4}^+$ under an aerobic condition was isolated and identified. The cell was motile and a Gram-negative rod, and usually occurred in pairs. By 16S-rDNA analysis, the isolated strain was identified as Enterobacter asburiae with 96% similarity. The isolate showed that the capacity of $N_2$ production under an oxic condition was approximately three times higher than that under an anoxic condition. Thus, the consumption of ${NH_4}^+$ by the isolate was significantly different in the metabolism of $N_2$ production under the two different environmental conditions. The optimal conditions of the immobilized isolate for $N_2$ production were found to be pH 7.0, $30^{\circ}C$ and C/N ratio 5, respectively. Under all the optimum reaction conditions, $N_2$ production by the immobilized isolate resulted in reduction of ORP with both the consumption of DO and the drop of pH. The removal efficiencies of $COD_{Cr}$, and TN were 56.1 and 60.9%, respectively. The removal rates of $COD_{Cr}$, and TN were the highest for the first 2.5 hrs with the removal $COD_{Cr}/TN$ ratios of 32.1, and afterwards the rates decreased as reaction proceeded. For application of the immobilized isolate to a practical process of ammonium removal, a continuous operation was executed with a synthetic medium of a low C/N ratio. The continuous bioreactor system exhibited a satisfactory performance at 12.1 hrs of HRT, in which the effluent concentrations of ${NH_4}^+$-N was measured to be 15.4 mg/L with its removal efficiency of 56.0%. The maximum removal rate of ${NH_4}^+$-N reached 1.6 mg ${NH_4}^+$-N/L/hr at 12.1 hrs of HRT(with N loading rate of $0.08\;Kg-N/m^3$-carrier/d). As a result, the application of the immobilized isolate appears a viable alternative to the nitrification-denitrification processes.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.1
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• pp.51-60
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• 1999

An intermittently-aerated, intermittently-decanted single-reactor process (KIDEA process : KIST intermittently decanted extended aeration process) was applied for nitrogen removal from wastewater. Synthetic wastewater with chemical oxygen demand (COD): nitrogen (N) ratio of approximately 5.25: 1 was used. The average COD removal efficiency reached above 95%, and under optimal conditions nitrogen removal efficiency also reached above 90%. This process consisted of 72 minute aeration, 48 minute settling and 24 minute effluent decanting with continuous feeding of influent wastewater from the bottom of the reactor, and did not require a separate anoxic mixing-phase. In this process, nitritation ($1^{st}$ step of nitrification) was induced but nitratation($2^{nd}$ step of nitrification) was suppressed. Main factors responsible for the accumulation of nitrite ion in the experimental condition were free ammonium and dissolved oxygen. This condition of nitrite build-up accelerated by continuous feed flow in the bottom of the KIDEA reactor because of high concentration of ammonia nitrogen in the influent. This research provides one of answers to control nitrate build-up.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.450-455
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• 2005

To treat wastewater efficiently by a one-step process of nitrogen removal, a new strain of $N_2-producing$ bacteria from $NH{_4}{^+}$ under an aerobic condition was isolated and identified. By 16S-rDNA analysis, the isolate was identified as Enterobacter asburiae with 96% similarity. The isolate shows that the capacity of $N_2$ production under an oxic condition was approximately three times higher than that under an anoxic condition. The optimal conditions (pH, temperature and C/N ratio) of the immobilized isolate for $N_2$ production were found to be 7.0, $30^{\circ}C$ and 5, respectively. Under all the optimum reaction conditions, the removal efficiency of $COD_{Cr}$ and TN reached 56.1 and 60.9%, respectively. The removal rates of $COD_{Cr}$ and TN were highest for the first 2.5 hrs (with the removal $COD_{Cr}$ ratios of 32.1), and afterwards the rates decreased as reaction proceeded. For application of the immobilized isolate to a practical process of ammonium removal, a continuous bioreactor system exhibited a satisfactory performance at HRT of 12.1 hr, in which the effluent concentrations of $NH{_4}{^+}-N$ was measured to be 15.4 mg/L with its removal efficiency of 56.0%. The maximum removal rate of $NH{_4}{^+}-N$ reached 1.6 mg $NH{_4}{^+}-N/L/hr$ at HRT of 12.1 hr (with N loading rate of 0.08 $Kg-N/m^3-carrier/d)$. As a result, the application of the immobilized isolate appears a viable alternative to the nitrification-denitrification processes.

• Horticultural Science & Technology
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• v.29 no.3
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• pp.255-259
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• 2011

Polyphenol oxidases (PPO) are copper-containing enzymes responsible for tissue browning in fruits and vegetables including potato, apple and pears. Although these enzymes have been studied for many years, their physiological roles in plants are not yet clear. Therefore, these enzymes need to be purified to characterize further from potato tubers. The classical methods used for the purification of PPO involve several steps. So in this study, we developed a one-step chromatography process for the potato tuber PPO purification. After removal of salts from dissolved ammonium sulfate precipitates of potato tuber extracts using Sephadex-G50 gel filtration, affinity chromatography was carried out on NHS-activated Sepharose 4B using p-aminobenzoic acid as a ligand. The purified enzyme was confirmed by silver staining and a zymogram. The optimum temperature and pH for the purified potato tuber PPO were $15^{\circ}C$ and pH 6.0, respectively. The results obtained in the present study will aid to evaluate PPO from various fruits and vegetables.

• Journal of Sensor Science and Technology
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• v.19 no.4
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• pp.291-296
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• 2010

Recently, recycling method of waste wafer has been an area of solar cell to cut costs. Micro_blasting is one of the promising candidates for recycling of waste wafer due to their extremely simple and cost-effective process. In this paper, we attempt to explore the effect of micro_blasting and DRE(damage removal etching) process for solar cell. The optimal process conditions of micro_blasting are as follows: $10{\mu}m$ sized $Al_2O_3$ powder, jetting pressure of 400 kPa, and scan_speed of 30 cm/s. And the particles formed on micro_blasted wafer were removed by DRE precess which was performed by using HNA(HF/$HNO_3$/$CH_3COOH$) and TMAH(tetramethyl ammonium hydroxide). Structural analysis was done using a-step and the XRD patterns.