• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.251-264
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• 2000

Organic removal from synthetic wastewater by electrochemical methods was investigated with various operating parameters, such as current density, retention time, electrode gap and $Cl^-/COD_{Cr}$ ratio. In electrolysis, dioxide iridium coated titanium ($IrO_2/Ti$) and stainless steel plate were used for anode and cathode respectively. The $COD_{Cr}$ removal efficiencies between plate type anode and net type anode were about same effect, but electrolytic power using net type anode is low than plate type anode. The $Cl^-/COD_{Cr}$ ratio was about $1.3kgCl^-/kgCOD_{Cr}$ when organic removal obtained 70 %, $Cl^-/COD_{Cr}$ ratio needs $2.2kgCl^-/kgCOD_{Cr}$ so as to organic completely remove. The removal efficiency of organics increased with current density, retention time and $Cl^-/COD_{Cr}$ ratio, but decreased with increasing electrode gap. The relationship of operating conditions and $COD_{Cr}$ removal efficiencies are as follows. $$COD_{Cr}(%)=80.0360(Current\;density)^{0.4451}{\times}(HRT)^{0.8102}{\times}(Gap)^{-0.4915}{\times}(Cl^-/COD_{Cr})^{0.5805}$$ There existed a competition between the removals for $COD_{Cr}$ and ammonium during electrolysis, the removal of ammonium was shown to be dominant and $COD_{Cr}$ removal was low. But $COD_{Cr}$ removal was raised as addition of alkalinity.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.107-116
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• 1993

This study is conducted to investigate treatability by activated sludge process for wastewater from acetaldehyde manufacturing plant. The optimum hydraulic retention time in aeration tank for removal of high strength substrate were measured. The removal efficiency were checked out by hydraulic retention time : 35hr., 40hr. and 45hr., respectively. $COD_{Cr}$, like substances were removed in all hydraulic retention time zone directed for efficiency, but non-biodegradable substances were remained. $COD_{Cr}$ biomass loading was 0.81kg $COD_{Cr}/kgMLVSS$ . day at 35hr. of retention time, 0.34 kg$COD_{Cr}$/kg MLVSS . day at 40hr., and O.l9kg$COD_Cr$/kgMLVSS . day at 45hr. And the mean $COD_{Cr}$, removal efficiency was 65.5%, 81.6% and 83.0%, respectively. And also $COD_{Cr}$, volume loading was 1.01kg$COD_{Cr}/m^3$ day, 0.87kg$COD_{Cr}/m^3$ - day, and 0.79kg$COD_{Cr}/m^3{\cdot }$day, respectively. The basic design parameter obtained is as fallows. The value of Specific substrate removal rate coefficient (k), Yield coefficient(Y) and Decay coefficient($k_d$) was $0.0013day^{-1}$, $0.505kgMLVSS/kgCOD_{Cr}$ and $0.040day^{-1}$, respectively.

• Journal of Environmental Science International
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• v.23 no.2
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• pp.181-192
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• 2014

In Korea, the chemical oxygen demand($COD_{sed}$) in freshwater sediments has been measured by the potassium permanganate method used for marine sediment because of the absence of authorized analytical method. However, this method has not been fully verified for the freshwater sediment. Therefore, the use or modification of the potassium permanganate method or the development of the new $COD_{sed}$ analytical method may be necessary. In this study, two modified $COD_{sed}$ analytical methods such as the modified potassium permanganate method for $COD_{Mn}$ and the modified closed reflux method using potassium dichromate for $COD_{Cr}$ were compared. In the preliminary experiment to estimate the capability of the two oxidants for glucose oxidation, $COD_{Mn}$ and $COD_{Cr}$ were about 70% and 100% of theoretical oxygen demand(ThOD), respectively, indicating that $COD_{Cr}$ was very close to the ThOD. The effective titration ranges in $COD_{Mn}$ and $COD_{Cr}$ were 3.2 to 7.5 mL and 1.0 to 5.0 mL for glucose, 4.3 to 7.5 mL and 1.4 to 4.3 mL for lake sediment, and 2.5 to 5.8 mL and 3.6 to 4.5 mL for river sediment, respectively, within 10% errors. For estimating $COD_{sed}$ recovery(%) in glucose-spiked sediment after aging for 1 day, the mass balances of the $COD_{Mn}$ and $COD_{Cr}$ among glucose, sediments and glucose-spiked sediments were compared. The recoveries of $COD_{Mn}$ and $COD_{Cr}$ were 78% and 78% in glucose-spiked river sediments, 91% and 86% in glucose-spiked lake sediments, 97% and 104% in glucose-spiked sand, and 134% and 107% in glucose-spiked clay, respectively. In conclusion, both methods have high confidence levels in terms of analytical methodology but show significant different $COD_{sed}$ concentrations due to difference in the oxidation powers of the oxidants.

• KSBB Journal
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• v.14 no.1
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• pp.119-123
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• 1999

A jet-loop reactor was used for the biological treatment of ethylene glycol(EG) which is a main component of polyester weight-loss wastewater, and is difficult to be removed by physicochemical treatments. Volumetric oxygen coefficient(kLa) of jet-loop reactor was significantly larfgeer that of air-lift reactor. When organic loading rates of synthetic polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$.day and 3.07 $kgCOD_{Cr}/m^3$.day, the effluent concentrations were measured as 154 $mgCOD_{Mn}/L$ and 156$mgCOD_{Cr}/L$, and removal efficiencies were found as 93%and 93.6%, respectively. The specific removal rate was proportionally increased from 0.25 to 1.60 $kgCOD_{Mn}$-removed/kgMLVSS.day as specific loading rate was increased from 0.25 to 1.72 $kgCOD_{Mn}$/kgMLVSS.day. Also, kinetics constants such as $K_s$, k, $K_d$, and Y were estimated as 89 mg/L, $0.05 hr^{-1}$, 0.1$day^{-1}$ and 0.78 respectively. When the organic loading rates of real polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$. and 5.24 $kgCOD_{Cr}/m^3$. day, the effluent concentrations were measured as 150 $mgCOD_{Mn}$/L, and 306 $mgCOD_{Cr}$/L, and removal efficiencies were found as 93.2% and 93%, respectively. This study demonstrated that EG in the wastewater could be efficiently removed biologically using a jet-loop reactor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1654-1660
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• 2009

Two different cutting-oils from H and B companies which are sold as an eco-friendly cutting-oils were selected and the biodegradability of these commercially available cutting-oils was evaluated by the sequencing batch reactor (SBR) processes. The cutting-oil wastes ($H_1$) pre-treated by coagulation/flocculation was used as an influent to SBR. When the F/M ratio was operated 0.04 to 0.08kgCOD/kgMLSS d, removals of $BOD_5$and $COD_{Cr}$were above 97% and 91%, respectively. T-N and T-P removals were above 76% and 81%, respectively. If the diluted cutting-oil wastes ($B_1$) was used as an influent of the SBR, $COD_{Cr}$removals were above 77% at the F/M ratio of 0.01-0.02kgCOD/kgMLSS d. After the cutting-oil wastes was treated by coagulation/ flocculation ($B_2$), $COD_{Cr}$removals was above 85%. If the pre-treated cutting-oil wastes were mixed with a synthetic wastewater ($B_3$) and fed into the SBR in order to mimic the real wastewater treatment plant situation, $BOD_5$and $COD_{Cr}$removals were above 97%, 91%, respectively. T-N and T-P removals were above 79% and 76%. The ratio between $BOD_5$and $COD_{Cr}$, ($COD_{Cr}$-$BOD_5$)/$COD_{Cr}$, indicating the biodegradability of effluent of the SBR, was calculated to 85% and 61%. This means that significant amounts of non-readily-biodegradable organic compounds in the effluent of $H_1$, $B_3$are still present.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.71-77
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• 2015

A fluidized biofilter was filled with Pseudomonas sp. and Bacillus cereus/thuringiensis-fixed waste-tire crumb media and was run to treat authentic textile-dyeing wastewater mixed with alkaline polyester-weight-reducing wastewater. As a result, its removal efficiency of $COD_{Cr}$ and color were 75~80% and 67%, respectively. In addition, upon constructing hybrid-recirculating system composed of the fluidized biofilter and a 450 W-UV/photocatalytic reactor, only fluidized biofilter was run bypassing UV/photocatalytic reactor at stage I. Subsequently, the hybrid system was continuously run at stage II-i, ii and iii. At stage II-i, the total removal efficiency of $COD_{Cr}$ was enhanced to be 80~85%, compared to 75% at stage I, owing to 20~30% removal efficiency of the UV/photocatalytic reactor. However, at stage II-i, the total removal efficiency of color was enhanced to be 65~70%, compared to 45~65% at stage I, even though the removal efficiency of the UV/photocatalytic reactor was tantamount to merely 0~5%. As far as the removal efficiency of fluidized biofilter of the hybrid-recirculating system is concerned, its removal efficiency of color was enhanced by the synergy effect of the hybrid-recirculating system unlike $COD_{Cr}$. Besides, despite of the increase of hybrid-recirculating system-recycle ratio, the deactivation of photo-catalytic activity was scarcely observed to eliminate the color while its irreversible deactivation was observed to eliminate $COD_{Cr}$.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.203-208
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• 2006

A continuous feed and cyclic draw SBR process was developed to overcome flow rate fluctuation and to maximize organic matters utilization efficiency for nitrogen and phosphorus removal. The developed SBR process was operated with two parallel reactors. Influent was supplied to one reactor which was not obligately aerated. At the same time, the other reactor was just aerated without supplying influent. In addition this mode was changed periodically. Cycle time was 6hr and aeration time ratio($t_{aer}/t_{total}$) was 0.33, respectively. $COD_{cr}$ and SS removal efficiencies of 95% or higher were achieved. Nitrogen removal was so greatly influenced by influent $COD_{cr}/T-N$ ratio. At influent $COD_{cr}/T-N$ ratio of 5.7, removal efficiencies of ammonia-N, T-N and T-P were 96%, 78% and 55%, respectively. Influent $COD_{cr}/T-N$ of 4 or higher ratio was necessary to achieve 60% or higher nitrogen removal. Organic matters of influent was efficiently utilized in denitrification reaction and consumed COD has a good correlation with removed T-N(about 6.5 mgCOD/mgTN). Continuous feed and cyclic draw SBR process could be one of alternative processes for the removal of nutrients in rural area where $COD_{cr}/T-N$ ratio was low and fluctuation of flow rate was severe.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.330-335
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• 1998

The objectives of this study are summarized with two. The one is to remove of $COD_{Cr}$, color and turbidity with coagulation and ozonation in nonbiodegradable landfill leachate, the other is to compare of water qualities with pre-ozonation and post-ozonation. The results are summarized as follows ; 1) 90 minutes ozonation with $75mgO_3/min$($4.5gO_3/hr$) was conducted at pH 4,7, 10 to remove $COD_{Cr}$. Removal efficiencies were investigated with 48.2%, 52.6%, and 62.3% respectively. As increasing pH, $COD_{Cr}$ removal efficiencies were increased, it was considered that hydroxyl radical($OH{\cdot}$) which strongly oxdize and nonselectively react with organic compounds, was rapidly produced by ozone self-decomposition at high pH. 2) Alum, ferric chloride and ferrous sulfate were used for coagulation as inorganic coagulant. Ferric chloride was investigated with optimal coagulant, and it removed $COD_{Cr}$ about 12.0% at pH5 and dosage of $2,000m{\ell}/{\ell}$. Cation(C-101P), anion(A-601P) and nonion(SC-050) were tested to remove organic pollutants in landfill leachate. Cation(C-101P) was investigated with the most effective organic coagulant, and removal efficiency of $COD_{Cr}$ was 19.8% at pH5 and dosage of $100m{\ell}/{\ell}$. 3) Color and turbidity were removed up to 88.6%, 97.0% at pH10, when contacted 90 minutes with ozone, respectively. These removal efficiencies were much higher than those of $COD_{Cr}$ and $COD_{Mn}$. It was considered that ozone could oxdize the triggering materials of color and turbidity selectively and preferentially. 4) $COD_{Cr}$, color and turbidity were more effectively removed with pre-ozonation than post-ozonation about 8%, 3.5% and 1% respectively. These results were well corresponed with other's studies that pre-ozonation will increase the effect of coagulation.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.837-845
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• 2017

A recirculating integrated system composed of a fluidized biofilter filled with waste-tire crumb media fixed with return sludge from wastewater treatment facility of D dyeing industrial center, and a UV/photocatalytic reactor packed with calcined $TiO_2$ coated-glass beads as photocatalyst-support, was constructed and was run to treat authentic textile-dyeing wastewater from D-dyeing industrial center, which was mixed with an alkaline polyester-weight-reducing wastewater and a wastewater from sizing process. As a result, its total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were ca. 81% and 55%, respectively. The synergy effect of the recirculating integrated system to enhance total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were evaluated at most ca. 7% and 3%, respectively. The fluidized biofilter and the UV/photocatalytic reactor were responsible for ca. 94% and 6% of the total $COD_{cr}$ removal efficiency, respectively, and were also responsible for ca. 86% and 14% of the total color-removal efficiency, respectively. Thus, the degree of the UV/photocatalytic reactor-unit process's contribution to RE(tot) of color, was about 2.4 times of that to RE(tot) of $COD_{cr}$. Therefore, the UV/photocatalytic reactor facilitated the more effective elimination of colors by breaking down the chemical bonds oriented from colors of dyes such as azo-bond, than $COD_{cr}$. In addition, the effect of the removal efficiency of each unit process(i.e., the fluidized biofilter or the UV/photocatalytic reactor) of the recirculating integrated system on RE(tot) of $COD_{cr}$ and colors, was analysed by establishing its model equation with an analytic correlation.

• International Journal of Highway Engineering
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• v.9 no.3
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• pp.75-82
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• 2007

Washed wastewater generated from the intermittent cleaning process of the three tunnel sites located in the Seoul area showed high concentrations of SS, $COD_{Cr}$, T-N, $NH_3-N$, $NO_3-N$, Zn, Cu, Cr(+6), Mn, Mg, Phenol, $CN^-$ and E-Coli based on the water quality analysis. These characteristics of the deteriorative wastewater depend on the sampling method, cleaning frequency, released amount of washing water, inner material of tunnel wall, traffic volume, and type of drainage systems. Gravitational separation experiment of SS with collected tunnel wastewater showed considerable removal of pollutants such as 80% of $COD_{Cr}$, 30% of T-N and 90% of T-P simultaneously. GAC isotherm test was conducted to remove dissolved portion of the pollutants, and resulted in high removal efficiencies above 80% of $COD_{Cr}$, T-N, Zn, Cu, Mn, Phenol, CN in the experimental condition of GAC dosage of $50g/1/{\ell}$.