• Title, Summary, Keyword: COD

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A Comparative Study on COD Fractionation Methods of Wastewater (하수의 COD 분류 시험 방법에 관한 비교 연구)

  • Kim, Sung-Hong;Yun, Jung-Won;Choi, Young-Gyun
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.4
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    • pp.387-394
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    • 2010
  • The influent COD of municipal wastewater has been divided into 4 fractions; readily soluble biodegradable, slowly particulate biodegradable, soluble and particulate unbiodegradable COD. The mathematical modeling of biological wastewater treatment processes and the design and operation of nutrient removal plants require a reliable and accurate estimate of the composition of influent wastewater COD. COD utilization rate is proportional to the oxygen uptake rate(OUR), so a batch biodegradation test with OUR measurement has been effectively used for the determination of COD fractionation. But the mathematical model of COD utilization and heterotrophs synthesis is essential to interpret the OUR measurement. Mamais method is another method for determining readily biodegradable soluble COD. Like the OUR test method, batch biodegradation test is necessary but it does not require mathematical model. These two methods for determining COD fractionation are introduced here in detail. Experimental results showed that COD composition by Mamais method is not different to that by OUR test method so, either of them can be used.

COD Pollutants Load Estimation Schemes in Lake Shihwa and Incheon Coastal Zone (시화호 및 인천연안의 COD 오염부하량 추정기법)

  • Cho Hong-Yeon;Cho Bum-Jun
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.18 no.3
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    • pp.262-267
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    • 2006
  • For the concentration management in COD parameters, it requires the measurement and estimation of the COD pollutants load (hereinafter PL) in the watershed. The estimation method of the PL, however, is provided only based on the BOD parameters. The development of COD PL estimation schemes is expected to execute total PL management in coastal zone and needs to more observation and much time. This study provides COD PL estimation schemes using statistical information about ratio analysis with COD & BOD concentration of rivers and drainages of an industrial complex in Lake Shiwha and Incheon Coastal Zone watershed. The COD PL is computed with ease by multiplying the conversion factor, which is calculated as the sum of the average and 1 to 3 (safety factors) times standard deviation. The conversion factor of Lake Shihwa and Incheon Coastal Zone is estimated as 1.7, 2.3 and 2.9 with respect to the safety factor 1, 2, and 3, respectively.

Removing High Concentration Organic Matters by Using Electrolysis (전기분해에 의한 고농도 유기물질 제거 특성)

  • Gil, Dae-Soo;Lee, Byung-Hun;Lee, Jea-Keun
    • 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.

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Evaluation of CODsed Analytical Methods for Domestic Freshwater Sediments: Comparison of Reliability and Correlationship between CODMn and CODCr Methods (국내 담수퇴적물의 CODsed 분석방법 평가: CODMn법과 CODCr법의 신뢰성 및 상관성 비교)

  • Choi, Jiyeon;Oh, Sanghwa;Park, Jeong-Hun;Hwang, Inseong;Oh, Jeong-Eun;Hur, Jin;Shin, Hyun-Sang;Huh, In-Ae;Kim, Young-Hoon;Shin, Won Sik
    • 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.

The Effect of Solubilization Pretreatment Process on Anaerobic Digestion of Waste Activated Sludge (전처리 가용화 공정이 잉여슬러지 혐기성 소화효율에 미치는 영향)

  • Yoo, Ho-Sik;Ahn, Seyoung
    • Journal of the Korea Organic Resources Recycling Association
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    • v.24 no.3
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    • pp.35-43
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    • 2016
  • COD properties of waste activated sludge (WAS) were investigated for various solubilization rate of mechanical pretreatment method in anaerobic digestion process. Inert COD was 37.0% of total COD in untreated WAS. Particulate biodegradable COD was converted to soluble biodegradables and particulate unbiodegradables as solubilization was processed. Particulate unbiodegradable portion of COD in WAS can be increased as particulate biodegradable portion is decreased in case of relatively long SRT of biological treatment. Thus, COD properties of WAS should be investigated in case of relatively low particulate biodegradable COD, because of possible low effect of solubilization. COD removal rate in anaerobic digester was enhanced as much as 2.1% and 15.1% for solubilization rate 5% and 35% due to pretreatment, respectively. COD removal rate was increased from 25% to 40%, and methane gas generation was increased from $607m^3/d$ to $907m^3/d$ as particulate COD of WAS was solubilized to 35% in pretreatment facilities.

Efforts of Specimen Sizes on Crack Opening Displacement (COD) for Submerged Arc Weldments of Fine Grained Steel (미세립강 잠호 용접부의 COD에 미치는 시편 크기의 영향)

  • 윤중근;김대훈;김문일
    • Journal of Welding and Joining
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    • v.1 no.2
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    • pp.53-60
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    • 1983
  • COD test based on fracture mechanics concept was used in this study to evaluate the fracture toughness quantitatively. Effects of specimen sizes on critical COD value for ABS EH 36 steel and its submerged arc weldments, and the variation of critical COD value depending on metallurgical/mechanical heterogeneities caused by weld thermal cycles were investigated. Experiment was performed by using specimens made from base metal and submerged arc weldments according to BS 5762. Obtained results are summarized as follows; 1) Critical COD value for base metal decreases with increasing thickness of specimen. On hand, as the reduction ratio of critical COD decreases with increasing specimen thickness, critical COD value becomes constant above a thickness of specimen. 2) Critical COD value for weldment decreases with increasing thickness of specimen and was also affected by metallurgical states of base metal. 3) Size effects for weldment was greater at the hardened region. 4) Critical COD value was affected by microstructural change due to weld thermal cycles in weldments; that is, accicular ferrite formation is favorable for increasing of COD value.

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Diagnosis of Wastewater Treatment Processes through the Wastewater COD Fractionation and Process Simulation I : Wastewater COD Fractionation (유입하수 유기물 분류 및 공정모사를 통한 하수처리공정 진단 I : 유입하수 유기물 분류)

  • Choi, Young-Gyun;Chung, Tai-Hak
    • Journal of Korean Society of Water and Wastewater
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    • v.21 no.5
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    • pp.513-520
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    • 2007
  • The simulation programs used for diagnosis and design of activated sludge process require organic fractions in municipal wastewater as the input variables. However, methods for characterizing organic fractions are still under development, and are not standardized. In this study, total COD of municipal wastewater was experimentally subdivided into readily and slowly biodegradable COD as well as soluble and particulate inert COD. The COD fractionation of the three municipal wastewater for one year shows linear relationship between each COD fraction and TCOD concentration with around 100% COD balance. This result means that the COD fraction do not vary very much with time, although the actual influent concentrations vary significantly with time and day. Therefore, the experimentally subdivided COD fractions can be utilized as wastewater specific parameters for the simulation of activated sludge processes.

Ecological modeling for estimation of a transport and distribution of COD in Kamak Bay (가막만의 COD 거동 및 분포 특성 평가를 위한 생태계 모델링)

  • Kim Dong-Myung
    • Journal of Environmental Science International
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    • v.14 no.9
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    • pp.835-842
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    • 2005
  • The three-dimensional eco-hydrodynamic model was applied to estimate the physical process in terms of COD (chemical oxygen demand) and net supply(or decomposition) rate of COD in Kamak Bay to find proper management plan for oxygen demanding organic matters. The estimation results of the physical process in terms of COD showed that transportation of COD is dominant in surface level while accumulation of COD is dominant in bottom level. In the case of surface level, the net supply rate of COD was 0 -0.50 mg/m2/day. The net decomposition rate of COD was 0 -0.04 mg/m2/day in middle level(3 -6m) and 0.05 -0.1 5 mg/m2/day in bottom level(6m -bottom). These results indicates that the biological decomposition and physical accumulation of COD are occurred predominantly at the northern part of bottom level. Therefore, it is important to consider both allochthonous and autochthonous oxygen demanding organic matters in the region.

Evaluation of Autochthonous COD in the Nakdong Estuary (낙동강 하구 해역의 자생COD 평가)

  • SHIN Sung-Kyo;PARK Chung-Kil;SONG Kyo-Ouk
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.28 no.3
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    • pp.263-269
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    • 1995
  • To determine the autochthonous COD caused by the production of phytoplankton, three different methods were used simultaneously utilizing several environmental factors and applied to the Nakdong Estuary. From the estimation of the tropic state index, tropic level in the Nakdong Estuary was found to be in excess of eutrophication level at all area studied. The percentage of autochthonous COD in total COD was largest in summer and in station No. 6 $(43.5\%)$. Using of the relationship between COD and salinity was not appropriate tov the evaluation of the autochthonous COD due to discrepancy with other tesulfs evaluated. However, the evaluations of autochthonous COD obtained from the $\DeltaCOO$ and the relationship between COD and chl.a were found to be proper methods, resulting in a relative error less than $20\%$ for all of the area investigated.

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A Study on the COD Removal in the Paste-board Wastewater by Activated Sludge Process (활성오니법에 의한 판지폐수중의 COD 제거에 관한 연구)

  • 도갑수;김영운
    • Journal of the Korean Professional Engineers Association
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    • v.18 no.3
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    • pp.28-35
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    • 1985
  • As the paper industry consumes much water in process and discharge wastewater containing suspended solid and COD(chemical oxygen demand), relevant law against this discharge has been set up to limit the total containment of COD in discharge. This study has been carried out to improve the treatment method for the soluble COD in wastewater produced during the process of paste-board production, which is made of semichemical pulp and waste paper. Applicated methods are, O$_2$AS : O$_2$ activated sludge process DAS : Deep well activated sludge process SAS : standard activated sludge process and proper combination of DAS and SAS 1) As a result of this experiment, we get the following conclusion between in COD sludge loading "X" and COD removable rate in the process of treating waste-water. COD removable rate(%)=(0.778+0.0146/X)${\times}$100(%)……(7) 2) In case that the COD sludge loading is high, it has been cleared out that the COD removable rate shall become low due to unknown unsoluble substances contained in the process. Meanwhile, to increase the efficiency rate of treatment, it is thought to be necessary, to provide long-time contacts with activated sludge. 3) Once the COD of original waste-water and the target COD of treated water are decided, COD sludge loading is obtained from equation(7), and capacity of aeration tank in the effective systems such as O$_2$AS, DAS, to bet the required COD removable rate can be decided. Therefore the choice among SAS, O$_2$AS, DAS methods is made in consideration of required COD removable rate and allowable installation area. 4) In the sedimentation tank with sludge bulking, it is possible to increase the COD removable rate by 3~7% but still there exist many obstacles to manage this operation.

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