• 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.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.327-328
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• 2005

Trace anions in high-sulfate wastewater from mainly derelict mines were determined by ion chromatography with on-line preconcentration and preelution technique. As the sample was preconcentrated and more strongly held ions were preeluted to the principal separation system, this approach was highly effective in removing large concentration of sulfate in high-sulfate wastewater. With this practical on-line preelution treatment, the peaks of fluoride and chloride showed good resolution even when the sulfate concentration was as high as 2000 mg/L and the analyzed total metal concentration was above 500 mg/L.

• Membrane and Water Treatment
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• v.9 no.1
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• pp.53-62
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• 2018

In this study, vacuum membrane distillation (VMD) was used to treat high-salinity wastewater (concentration about 17%) discharged by chlor-alkali plant after resin regeneration. The feasibility of VMD for the treatment of real saline wastewater by using Polyvinylidene fluoride (PVDF) microporous plate membrane with a pore diameter of $0.2{\mu}m$ was investigated. The effects of critical operating parameters such as feed temperature, velocity, vacuum degree and concentration on the permeate water flux were analyzed. Numerical simulation was used to predict the flux and the obtained results were in good agreement with the experimental data. The results showed that an increase in the operating conditions could greatly promote the permeate water flux which in turn decreased with an increase in the concentration. When the concentration varied from 17 to 25%, the permeate water flux dropped marginally with time indicating that the concentration was not sensitive to the decrease in permeate water flux. The permeate water flux decreased sharply until zero due to the membrane fouling resistance as the concentration varied from 25 to 26%. However, the conductivity of the produced water was well maintained and the average value was measured to be $4.98{\mu}s/cm$. Furthermore, a salt rejection of more than 99.99% was achieved. Overall, the outcome of this investigation clearly indicates that VMD has the potential for treating high-salinity wastewater.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.257-262
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• 2013

The fluorine-containing waste water tends to show a higher removal efficiency through the coagulative precipitation process with calcium. However the tetrafluoroborate produced from the etching process is difficult to remaval due to it's low reactivity with calcium. The objective of this study is improving the efficiency of fluoride ion removal in tetrafluoroborate through decomposing. Research on tetrafluoroborate decomposition depending on reaction pH, temperature, and aluminum dosage were conducted, using a laboratory-scale reactor. The result shows that the reaction of tetrafluoroborate with aluminum is faster with lower pH, higher water temperature, and higher Al/T-F (Aluminum/Total Fluoride) mole ratio. It is found that there was no big change in concentration after over 120 minutes of reaction. This study is to be able to improve the efficiency of tetrafluoroborate and fluoride wastewater treatment by using aluminum.

• Membrane and Water Treatment
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• v.11 no.5
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• pp.333-344
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• 2020

Advances in industrial development and waste management over several decades have reduced many of the impacts that previously affected ecosystems, however, there are still processes which discharge hazardous materials into environments. Among industries that produce industrial wastewaters, textile manufacturing processes play a noticeable role. This study was conducted to test a novel continuous combined commercial membrane treatment using polyvinylidene fluoride (PVDF), ultrafiltration (UF), and polyamide (PA) nanofiltration (NF) membranes for textile wastewater treatment. The synthetic textile wastewater used in this study contained sodium silicate, wax, and five various reactive dyes. The results indicate that the removal efficiency for physical particles (wax and resin) was 95% through the UF membrane under optimum conditions. Applying UF and NF hybrid treatment resulted in total effective removal of dye from all synthetic samples. The efficiency of sodium silicate removal was measured to be between 2.5 to 4.5% and 13 to 16% for UF and NF, respectively. The chemical oxygen demand in all samples was reduced by more than 85% after treatment by NF.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.651-654
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• 2016

A number of accidents relating to highly toxic hydrogen fluoride (HF) or hydrofluoric acid (HA) release have occurred over fast few decades in Korea. Thus, this study was conducted to investigate the fluoride (F) concentrations in paddy soil and brown rice from 2 different areas where the soils were exposed to HF and HA. In the first case, the HF leakage accident that occurred in 2012 affected the surrounding soils and crops and consequently, crops (rice) affected by HF were unavailable for forage even though F did not accumulate in the soil. For example, at the time of accident, F concentrations in brown rice samples were $33.0-1,395mg\;kg^{-1}$, while F concentrations in soil samples were $155-295mg\;kg^{-1}$ which were less than the Korean standard guideline values of $400mg\;kg^{-1}$. However, after a year, F concentrations in brown rice were observed below the detection limit ($1mg\;kg^{-1}$), although F concentrations in soils were similar with those in 2012. Also, large amounts of wastewater discharges containing HA occurred in 2013 and some agricultural soils exceeded the Korean standard guideline values for F ($400mg\;kg^{-1}$), but soil-plant F transfer was not observed. In conclusion, it was observed that soil to plant transfer of F is unlikely although HF and HA as gas or liquid form can cause direct damage to plants.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.3
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• pp.118-124
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• 1998

To use chlorine residual as an surrogate parameter of the water quality change during the transportation in the water distribution system(WDS), the correct prediction model of chlorine residual must be established in advance. This paper shows the procedure and the result of applying the water quality model to the field WDS. To begin with, hydraulic model was calibrated and verified using fluoride as an tracer. And chlorine residual was predicted through simulation of water quality model. This predicted value was compared with the observed value. With adjusting the bulk decay coefficient(kb) and the wall decay coefficient(kw) according to the pipewall environment, the predicted chlorine residual can represent the observed value relatively well.

• Membrane Journal
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• v.18 no.2
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• pp.109-115
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• 2008

To remove total dissolved solid (TDS) from wastewater, a carbon membrane system was prepared, using carbon membranes made from conductive activated carbon and poly(vinylidene fluoride) (PVDF). Using 100 ppm aqueous solutions of NaCl, $Na_2SO_4,\;MgCl_2,\;MgSO_4$, the basic properties of the carbon membranes used were studied. For the treatment of the real dye wastewater supplied from Kyungin Corp., a pilot scale carbon membrane system was also prepared, which was consisted of 240 plies of carbon membranes of $20cm{\times}20cm$ (length${\times}$width). Using the real wastewater with different TDS such as 941, 2050, 2810, 3830, 4960, 6030 ppm, prepared by the dilution of the original wastewater with pure water, the performance of the pilot scale carbon membrane system was studied. The effect of the operational conditions was studied.

• Journal of Korean Society on Water Environment
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• v.35 no.5
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• pp.418-424
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• 2019

In this study, $TiO_2$ nanotubes with different morphologies were prepared in the electrolyte consisting of ethylene glycol, ammonium fluoride($NH_4F$), and deionized water($H_2O$) by controlling the voltage and time in the anodization method. Thicknesses and pore sizes of these $TiO_2$ nanotubes were measured to interpret the relationship between anodization conditions and $TiO_2$ nanotube morphologies. Element contents in the $TiO_2$ nanotubes were detected for further analysis of $TiO_2$ nanotube characteristics. Photoelectrolyticdecolorization efficiencies of the $TiO_2$ nanotube plates with various morphologies were tested to clarify the morphology that a highly active $TiO_2$ nanotube plate should have. Influences of applied voltage in photoelectrolysis processes and sodium sulfate($Na_2SO_4$) concentration in wastewater on the decolorization efficiency were also studied. To save the equipment investment cost in photoelectrolysis methods, a two-photoelectrode system that uses the $TiO_2$ nanotube plates as photoanode and photocathode instead of adding other counter electrodes was studied. Compared with single-photoelectrode system that uses the $TiO_2$ nanotube plate as photoanode and titanium plate as cathode on the view of the treatment of dye wastewater containing different amounts of salt. As a result, a considerably suitable voltage was strictly needed for enhancing the photoelectrolyticdecolorization effect of the two-photoelectrode system but if salts exist in wastewater, an excellent increase in the decolorization efficiency can be obtained.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1127-1137
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• 2000

Applications of lanthanum ion and crude rare earth chloride to the phosphate wastewater and fluorine wastewater, respectively, as treatment agents were studied. For the investigation of phosphate removal characteristics according to the amount of lanthanum ion, initial phosphate content was decreased by about 50% when molar ratio of [$La^{3+}$]:[$PO_4{^{3-}}-P$] was 0.25 and nearly all of phosphate was removed when the molar ratio of [$La^{3+}$]:[$PO_4{^{3-}}-P$] to be doubled. The removal of phosphate by $La^{3+}$ appeared to reach equilibrium state rapidly, and it was exothermic reaction since the removed amount of phosphate was diminished somewhat when the reaction temperature was increased. The zeta potential of combined particulate compound of lanthanum ion and phosphate was located for its isoelectric point at pH 5.5 and the turbidity of treated wastewater was found to vary according to the pH in a similar manner as the absolute value of zeta potential of the combined particulate compound did. For the treatment of fluorine wastewater by crude rare earth chloride, the remaining fluorine content after treatment decreased as the dosage of crude rare earth chloride increased. Whereas, the turbidity of treated wastewater and the amount of sludge generated were shown to increase as more crude rare earth chloride was added. The remaining fluorine content and the turbidity of treated wastewater were decreased and the amount of sludge generated was observed to increase according the increase of coagulant dosage under the condition of constant input of crude rare earth chloride.