• Title, Summary, Keyword: COD reduction

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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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Marine Ecosystem Response to Nutrient Input Reduction in Jinhae Bay, South Korea

  • Oh, Hyun-Taik;Lee, Won-Chan;Koo, Jun-Ho;Park, Sung-Eun;Hong, Sok-Jin;Jung, Rae-Hong;Park, Jong-Soo
    • Journal of Environmental Science International
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    • v.15 no.9
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    • pp.819-827
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    • 2006
  • We study on the dynamic interaction with a simulated physical-biological coupled model response to nutrient reduction scenario in Jinhae Bay. According to the low relative errors, high regression coefficients of COD and DIN, and realistic distribution in comparison to the observation, our coupled model could be applicable for assessing the marine ecosystem response to nutrient input reduction in Jinhae Bay. Due to the new construction and expansion of sewage treatment plant from our government, we reduce 50% nutrient inputs near Masan Bay and sewage treatment plant. COD achieves Level II in Korea standard of the water quality from the middle of the Masan Bay to all around Jinhae Bay except the inner Masan Bay remaining at Level III. When our experiment reduces 50% nutrient inputs near Masan Bay and Dukdong sewage treatment plant simultaneously, COD decreases to about 0.1-1.2 mg/L $(128^{\circ}30'{\sim}128^{\circ}40'\;E,\;35^{\circ}05'{\sim}35^{\circ}11'\;N)$. The COD from the middle of the Masan Bay to Jinhae Bay achieves Level II.

A Study on the Effect of Initial pH and Cultivation Temperature of Substrate on the Biomass Production and COD-reduction in the Yeast Cultivation in Sugar Beet Stillages (사탕무 알콜증류폐액을 기질로 효모균체를 생산할 때 기질의 초기 pH와 배양온도가 균체생산량과 COD감소에 미치는 영향)

  • Lee, Ki Young
    • Journal of the Korea Organic Resources Recycling Association
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    • v.13 no.4
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    • pp.100-106
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    • 2005
  • Sugar beet stillages were used as a substrate for the production of single cell protein by the thermotolerant yeasts Candida rugosa, Kluyveromyces marxianus and C. utilis. The biomass production increased in accordance with the increase of pH-value, but protein content decreased. C. rugosa showed the highest crude protein production as 3.68g/l and C. utilis 2.9g/l, Kl. marxianus 2.30g/l, respectively. The rate of COD reduction in stillage versus crude protein production of C. rugosa showed the highest value as 0.35~0.39g/l as a good strain for single cell protein production using sugar beet stillages.

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A Case Study for Installation of Dry Washing Process in Kitchen (주방에서 건식 식기 세척기 설치 및 운전 사례연구)

  • Tateda, Masafumi;Kim, Youngchul
    • Journal of Korean Society on Water Environment
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    • v.23 no.3
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    • pp.391-396
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    • 2007
  • Dry washing by air and sand to clean dishes was investigated for establishing a dry washing process in a kitchen. Thirty seasonings and foods as dirt markers and fourteen kinds of dishes were used for the experiment, and washing efficiency was evaluated by COD-MN (mg/L). It was found that air dry washing effectively reduced COD-MN of some dirt markers but not effective at all to some dirt markers. It could be also said that dirt markers would not be completely removed by air dry washing. The shape of dishes also affected COD-MN reduction by air dry washing. Sand dry washing showed excellent efficiency on COD-MN reduction. Combination of air and sand dry washing may be necessary to make a dish dry washing system which is completely independent from water.

Estimation of Sludge Reduction and Nitrogen Removal Possibility using OSA Process (OSA 공정을 이용한 하수슬러지 감량화 및 질소제거 가능성 평가)

  • Joo, Jae-Young;Yoon, Su-Chul;Nam, Duck-Hyun;Park, Chul-Hwi
    • Journal of Korean Society of Water and Wastewater
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    • v.22 no.5
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    • pp.497-503
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    • 2008
  • The Oxic-Settling-Anaerobic(OSA) process is a modified activated sludge processes for sludge reduction. It is evaluated that the sludge production in OSA process can decrease to 88% because of biomass decay and kinetic parameter($Y_H$ 0.237mgVSS/mgCOD, $b_H$ $0.195d^{-1}$) in anaerobic reactor, when compared with CAS process. However, it has problems caused by sludge reduction such as increase of nutrient loading. In case that the anoxic condition through the introduction of the intermittent aeration for the enhancement of nitrogen removal ability build up and enough rbCOD is suppled, maximum 88% of nitrogen is removed in the OSA process. If the OSA process optimizing the intermittent aeration cycle is applied to the separate sewage system with high rbCOD fraction, it can be converted to advanced process in terms of the sludge reduction and nitrogen removal, simultaneously.

Bycatch Reduction by Experimental Shaking Codend Attached with Canvas in a Bottom Trawl

  • Kim, Yonghae
    • Fisheries and aquatic sciences
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    • v.18 no.3
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    • pp.325-332
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    • 2015
  • An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

Ecosystem Modelling for Improvement Summer Water Quality of Jinhae Bay in 2003 (2003년 하계 진해만 수질 개선을 위한 생태계 모델링)

  • Hong, Sok-Jin;Lee, Won-Chan;Jung, Rea-Hong;Oh, Hyun-Tek;Jang, Ju-Hyung;Goo, Jun-Ho;Kim, Dong-Myung
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.13 no.2
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    • pp.103-110
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    • 2007
  • This study estirmted the appropriate pollutant load reduction from point sources in Jinhae Bay, Korea, using an eco system model. The results of COD values in the inner part of the bay obtained through the simulation by ecosystem model were greater than 3.0mg/L, and exceeded the limits of Korean Coastal Water Quality Grade III. Engineering countermeasures to reduce the $70\sim90%$ of all land based pollution load or organic and inorganic material loads from point sources by more than 50% were required to keep the COD levels below 2 mg/L. The reduction loads is 5,632kg/day of COD, 481kg/day of DIP and 7,991 kg/day of DIN in case of the reduction of both the organic and nutrients. The estimated environmental currying capacity of that case is 13,112kg/day of COD, 206kg/day of DIP and 3,425kg/day of DIN to keep the COD levels below 2mg/L.

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An Estimation Study of Watershed Pollution Load Reduction Using Environmental Capacity (환경용량을 고려한 유역 오염부하삭감량 추정 연구)

  • Jung, Jae-Sung;Park, Young-Ki;Kim, Jong-Guk
    • Journal of Korean Society of Environmental Engineers
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    • v.28 no.12
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    • pp.1265-1273
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    • 2006
  • The environmental capacity and watershed pollution load reduction of Yongdam reservoir were estimated by the simulation of water quality variation process with the target water quality establishment, pollution load estimation and flow analysis. The potable raw water $I{\sim}II$, COD $1.0{\sim}3.0$ mg/L and TP $0.01{\sim}0.03$ mg/L were selected as the target water quality Yongdam reservoir water quality model was constructed with WASP5 contained 42 segments and the correlation of calibrated results were BOD 0.73, $PO_4-P$ 0.98. The environmental capacity for target quality COD 2.0 mg/L and TP 0.02 mg/L were BOD $131,880{\sim}4,694$ kg/d, TP $7,855 {\sim}167$ kg/d which were less than exists, and the related reduction ratios were BOD $51{\sim}62%$, TP $47{\sim}67%$ which were middle amount in exists. The load reduction ratios to meet the potable raw water $I{\sim}II$ were BOD $72{\sim}16%$, TP $78{\sim}36%$ in existing conditions and BOD $81{\sim}44%$, TP $84{\sim}52%$ in new conditions. BOD was the least one and TP was the second least in 4 results. The effects of the load reduction assignment to subbasin were dominant in TP but little in COD.

Enhanced and Balanced Microalgal Wastewater Treatment (COD, N, and P) by Interval Inoculation of Activated Sludge

  • Lee, Sang-Ah;Lee, Nakyeong;Oh, Hee-Mock;Ahn, Chi-Yong
    • Journal of Microbiology and Biotechnology
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    • v.29 no.9
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    • pp.1434-1443
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    • 2019
  • Although chemical oxygen demand (COD) is an important issue for wastewater treatment, COD reduction with microalgae has been less studied compared to nitrogen or phosphorus removal. COD removal is not efficient in conventional wastewater treatment using microalgae, because the algae release organic compounds, thereby finally increasing the COD level. This study focused on enhancing COD removal and meeting the effluent standard for discharge by optimizing sludge inoculation timing, which was an important factor in forming a desirable algae/bacteria consortium for more efficient COD removal and higher biomass productivity. Activated sludge has been added to reduce COD in many studies, but its inoculation was done at the start of cultivation. However, when the sludge was added after 3 days of cultivation, at which point the COD concentration started to increase again, the algal growth and biomass productivity were higher than those of the initial sludge inoculation and control (without sludge). Algal and bacterial cell numbers measured by qPCR were also higher with sludge inoculation at 3 days later. In a semi-continuous cultivation system, a hydraulic retention time of 5 days with sludge inoculation resulted in the highest biomass productivity and N/P removal. This study achieved a further improved COD removal than the conventional microalgal wastewater treatment, by introducing bacteria in activated sludge at optimized timing.

제약폐수 활성슬러지 공정에서 DO농도에 따른 미생물의 활성 변화 측정

  • Mun, Sun-Sik;Lee, Sang-Hun;Sin, Jong-Cheol;Choe, Gwang-Geun;Lee, Sang-Hun;Mun, Heung-Man;Lee, Jin-Won
    • 한국생물공학회:학술대회논문집
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    • pp.355-358
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    • 2002
  • In this study, we have tried to find the maximum microbial efficiency at the various dissolved oxygen (DO) concentration conditions in the treatment of pharmaceutical wastewater. Experiments of activated sludge process were performed to examine the relation between microbial activity and DO concentration in a continuous bioreactor. The reduction rate of COD (chemical oxygen demand) was low at the DO concentration between 0 ppm and 1.0 ppm, but it went higher and showed maximum between 1.5 ppm and 3.0 ppm. Then the COD reduction rate was quickly decreased above the DO concentration of 3.0 ppm.

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