• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.253-261
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• 2015

The purpose of this study is the efficient biological treatment of highly concentrated nitrate nitrogen by calcium ion control present within the pickling wastewater. In laboratory scale's experiments research was performed using a sequencing batch reactor and the evaluation of denitrification reaction in accordance with the injection condition of calcium ions, the surface properties of microorganisms, and the evaluation of sludge precipitability were performed. Results of the study showed that the denitrification reaction was delayed when injecting more than 600 mg/L of the calcium ion within the denitrification process. In addition, we observed the absorption form of calcium ions absorbed on the surface of microorganisms following an increase in the calcium ion dose. It was found that as the calcium ion dose increased the sludge precipitability also increased continuously and it is judged that a smooth denitrification induction is possible when treating the nitrate nitrogen by the calcium ion control of pickling waste water and the shortening of precipitation time enables a liquid operation to increase the reaction time.

• Journal of Environmental Science International
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• v.18 no.6
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• pp.645-654
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• 2009

Lab-scale Electrodialysis(ED) system with different membranes combined with before or after pyroma process were carried out to remove nitrate from two pickling acid wastewater containing high concentrations of $NO_3\;^-$(${\approx}$150,000 mg/L) and F($({\approx}$ 160,000 mg/L) and some heavy metals(Fe, Ti, and Cr). The ED system before Pyroma process(Sample A) was not successful in $NO_3\;^-$ removal due to cation membrane fouling by the heavy metals, whereas, in the ED system after Pyroma process(Sample B), about 98% of nitrate was removed because of relatively low $NO_3\;^-$ concentration (about 30,000 mg/L) and no heavy metals. Mono-selective membranes(CIMS/ACS) in ED system have no selectivity for nitrate compared to divalent-selective membranes(CMX/AMX). The operation time for nitrate removal time decreased with increasing the applied voltage from 10V to 15V with no difference in the nitrate removal rate between both voltages. Nitrate adsorption of a strong-base anion exchange resin of $Cl\;^-$ type was also conducted. The Freundlich model($R^2$ > 0.996) was fitted better than Langmuir mode($R^2$ > 0.984) to the adsorption data. The maximum adsorption capacity ($Q^0$) was 492 mg/g for Sample A and 111 mg/g for Sample B due to the difference in initial nitrate concentrations between the two wastewater samples. In the regeneration of ion exchange resins, the nitrate removal rate in the pickling acid wastewater decreased as the adsorption step was repeated because certain amount of adsorbed $NO_3\;^-$ remained in the resins in spite of several desorption steps for regeneration. In conclusion, the optimum system configuration to treat pickling acid wastewater from stainless-steel industry is the multi-processes of the Pyroma-Electrodialysis-Ion exchange.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.774-781
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• 2011

Nitric acid and hydrofluoric acid are used for acid pickling in zirconium alloy tubing manufacturing process. Nitrate and fluoride in the wastewater were treated by chemical coagulation and SOD (Sulfur Oxidation Denitrification) process. This study is investigated the effect of fluoride concentration and the optimal condition for SOD process. The limited fluoride concentration for SOD process was below 20 mg F-/L. The adjusted pH and alkalinity by NaOH and $NaHCO_3$ was shown to be more effective for removal of nitrate compared with using NaOH. Furthermore, the microbial activator mixed trace elements and ingredient for alkalinity did not only supplement with alkalinity but also enhance the growth and proliferation for sulfur-oxidizing bacteria. As a result, the inorganic industrial wastewater was successfully treated by the microbial activator in SOD process without continuous addition of seed sludge. Finally, SOD process was shown to remove nitrate in industrial wastewater and to contribute the microbial activator for activation of sulfur-oxidizing bacteria.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.855-859
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• 2011

The main pollutants from zirconium alloy tubing manufacturing process in nuclear industry are nitrate ($NO_3-N$) and fluoride (F-)Nitric acid, and hydrofluoric acid is used for acid pickling. The process for the removal of nitrate and fluoride is composed of 1st chemical coagulation, SOD (Sulfur Oxidation Denitrification) process using sulfur-oxidizing denitrification, and 2nd chemical coagulation. The characteristic of the wastewater treatment is an application of SOD process. The SOD Process is highly received attention because it is significantly different from existing processes for sulfur denitrification. A JSC (JeonTech-Sulfur- Calcium) Pellet is unification of sulfur and alkalinity material. According to result of SOD process in wastewater treatment plant, the removal efficiency of T-N was over 91% and the average concentration of T-N from influent was 147.55 mg T-N/L and that from effluent was 12.72 mg T-N/L. Therefore, SOD process is a useful to remove nitrogen from inorganic industrial wastewater and a new development of microbial activator was shown to be stable for activation of autotrophic bacteria.