• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.295-307
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• 2002

Water temperature, salinity, and DO concentration were measured vertically in the Chinhae-Masan Bay over the course of 1 year. The characteristics of the stratification were analysed using the measured water temperature and salinity data. The vertical DO concentration changes were also analysed through consideration of the degree of stratification and the level of sediment pollution. The results of the analyses show that the thermal stratification appears just before April and disappears after October. The salinity differences between the surface and the bottom were 3.9(equation omitted), 9.3 (equation omitted), 4.3(equation omitted) in April, August, and October, respectively. The DO concentration change averaged over water depth was 2.6(mg/L) in April; 8.3(mg/L) in June: 5.9(mg/L) in August; 7.2(mg/L) in September; and 4.4(mg/L) in October. The DO concentration changes were closely related to the levels of contamination and also to the effect of the mass-transfer inhibition between the surface and bottom layers due to the thermal and density stratification.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.431-431
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• 2016

J 호소는 1942년도에 충청남도 아산시 선장면에 설치된 농업용 저수지로서, 현재 COD, TN, TP 모두 등급외의 수질상태를 보이고 있다. J 호소 상류 유역은 축산농가가 다수 위치하고 있으며, 설치된 지 70년이 지난 노후화된 저수지로 고농도의 오염물질 유입뿐만 아니라 호소 바닥의 오염 퇴적물에 의한 내부 부하가 중요한 수질오염원이 되고 있다. 호소의 수질은 현재 COD 10.6~16.5 mg/L, Chl-a $75mg/m^3$ 이상으로 수질오염도가 매우 높으며, 특히 늦봄에서 초가을까지 외기온도 상승 및 저수율 저하와 함께 부영양화 증가, 녹조 대발생 등으로 호 내 물고기 대량 폐사 및 악취발생 등으로 민원이 다수 발생하고 있다. 이러한 현상의 직접적인 원인은 수중의 DO 농도 결핍이며, 따라서 수중의 DO 농도를 일정수준 이상으로 유지시켜 주는 것은 호소 수질관리를 위해 매우 필요하다고 판단된다. 본 연구에서는 공기 중의 산소를 호소 수체에 포기시켜 주는 마이크로버블 발생장치를 J 저수지에 설치하여 수체의 DO 농도 변화 등을 분석하였고, 본 연구결과는 농업용 호소의 수질개선을 위한 기술개발 및 계획수립의 기초자료로 활용하고자 하였다. 마이크로버블 포기장치는 수심이 약 4m 되는 저수지 제방 근처에 100m 간격으로 총 3지점에 설치하였다. 버블 발생기는 기액 2상류 선회형 마이크로 버블 발생장치로 3지점에 각 1set(1set에 3기로 구성)씩 구성하여 저수지 바닥 층에서 상부로 1m 떨어진 지점에 고정식으로 설치하였다. 총 공기흡입량은 380 LPM이며, 사용동력은 12.2kW를 사용하였다. 마이크로 버블 포기장치 설치 후 호 내 DO 농도 변화를 평가하기 위하여 호소 전체에 18개 지점을 선정하여 수심 50cm 간격으로 DO 농도를 측정하였다. 가동 전에는 DO 평균농도가 표층에서는 약 7.7mg/L로 나타났고, 수심에 따라 거의 수직적으로 감소하여 바닥층에서는 약 0.2mg/L로 거의 무산소 상태를 보이고 있었다. 마이크로 버블 가동 2주 후에는 수심 3m까지의 모든 수층에서 DO 농도가 약 6.0mg/L 이상을 보였고, 바닥층에서는 DO 약 3.4mg/의 농도를 나타내었다. 가동 3주 후에도 2주 후와 비슷한 수치를 보이고 있었으나 가동 4주가 지나면서부터는 호소 바닥층(수심 3.5m)에서도 DO 농도가 7.0mg/L 이상의 높은 농도를 유지하는 것으로 조사되었다. 호소 저층에서 호기성 상태의 지속적 유지는 퇴적 오염물질이 수층으로 용출되는 것을 예방할 수 있으므로 마이크로버블을 잘 활용하면 호소의 악취제거 및 수질개선에 많은 도움이 될 것으로 판단된다.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.283-288
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• 1999

The effect of dissolved oxygen(DO) concentration on the growth of Pseudomonas aeruginosa and it's mutant M-10 was studied the growth kinetics and the possibility of waste treatment for reducing the amount of excess sludge. Different DO concentrations on the growth of wild type Pseudomonas aeruginosa affected to cellular yields, decreasing with increasing DO concentrations. Under these conditions, the maximum 14 folds decrease of cellular yield was achieved at 90 ppm DO levels by screened, being able to reduce their cellular yields under low DO concentration. The optimum mutation conditions were obtained by the treatment of NTG mutagen at 30${\circ}C$ for 1 hr. The growth characteristics of the selected mutant M-10 showed the same as the wild type growth kinetics. However, cellular yields are significantly decreased to 55% compared with those of wild type under DO concentrations increased. We, therefore, expect the application of the mutants to waste treatment for reducing excess sludge.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.238-245
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• 2021

In this study, we carried out case study to predict dissolved oxygen (DO) concentration of Nakdong river estuary with LSTM model. we aimed to figure out a optimal model condition and appropriate predictor for prediction in dissolved oxygen concentration with model parameter and predictor as cases. Model parameter case study results showed that Epoch = 300 and Sequence length = 1 showed higher accuracy than other conditions. In predictor case study, it was highest accuracy where DO and Temperature were used as a predictor, it was caused by high correlation between DO concentration and Temperature. From above results, we figured out an appropriate model condition and predictor for prediction in DO concentration of Nakdong river estuary.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.110-114
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• 2000

Effects of the combinations of six oxygen concentrations ($control, 0.6, 1.0, 2.0, 3.4 and 7.4 mg DO/l$) and two salinity levels ($20{\%_{\circ}} and 32{\%_{\circ}}$) on the rates of oxygen consumption, ammonia excretion and mortality of the mysid, Neomysis awatschensis were tested at $20{\circ}C$. The lethal level ($96 hr-LC-(50)$) of dissolved oxygen for mysid at $20{\%_{\circ}} and 32{\%_{\circ}} were 2,20 mg DO/l and 1.60 mg DO/l$ respectively, and all mysids died within $24hr at 0.6 mg DO/l$. Oxygen consumption rate of mysid was increased with dissolved oxygen increase at $20{\%_{\circ}} and 32{\%_{\circ}}$, but ammonia excretion rate was high af $1.0 mg DO/l$ during 96h exposure to DO concentration, and significantly greater in $20{\%_{\circ}} than 32{\%_{\circ}}$. $O:N$ ratio of mysid exposed during 96hr with salinity anil dissolved oxygen was below $10 at 20{\%_{\circ}} and 1,0{\~}2.0 mg DO/l, and was 4.4 at 32{\%_{\circ}} and 1.0 mg DO/l$. These results indicated that mysids were capable of changing their energy substrate in response to salinity and DO changes, and obtaining energy from proteins.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.724-729
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• 2013

Simultaneous nitrification and denitrification (SND) occurs concurrently in the same reactor under micro dissolved oxygen (DO) conditions. Anaerobic zone was applied for phosphorus release prior to an aerated membrane bio-reactor (MBR), and anoxic zone was installed by placing a baffle in the MBR for enhancing denitrification even in high DO concentration in the MBR. Phosphorus removal was tested by alum coagulation in the anaerobic reactor preceding to MBR. DO concentration were 2.0, 1.5, 1.0, 0.75 mg/L in the MBR at different operating stages for finding optimum DO concentration in MBR for nitrogen removal by SND. pH was maintained at 7.0~8.0 without addition of alkaline solution even with alum addition due to high alkalinity in the raw sewage. Both TCODcr and $NH_4^+$-N removal efficiency were over 90% at all DO concentration. TN removal efficiencies were 50, 51, 54, 66% at DO concentration of 2.0, 1.5, 1.0, 0.75 mg/L, respectively. At DO concentration of 0.75 mg/L with addition of alum, TN removal efficiency decreased to 54%. TP removal efficiency increased from 29% to 95% by adding alum to anaerobic reactor. The period of chemical backwashing of the membrane module increased from 15~20 days to 40~50 days after addition of alum.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.385-398
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• 2007

It was analysed that spatial and temporal change patterns of general water quality constituents were measured monthly from 2002 to 2005 in Jumunjin Harbour. The measured constituents are temperature, salinity, pH, SS and DO. Concentration difference of upper lower layer for general water quality constituents was small. Temperature and DO concentration show the clear difference at temporal concentration change pattern, but SS, pH and salinity have irregular change pattern. Also, water quality improvement effect of seawater exchange facilities and sewage treatment plants is analysed quantitatively using averaged spatial and temporal data set. From this result, it is found that effect of sewage treatment plants is small and seawater exchange facilities at zone 1 and 2 is clear concentration reduction effect to be about 26% and 16%, respectively. After sewage treatment plants operation, DO concentration reduced about 10% at inner zone of Jumunjin Harbour, the other side, after seawater exchange facilities concentration DO concentration increased about 10%. DO concentration at 2005 estimated little than that of 2002, it is concluded that a yearly change of DO concentration has about 10%.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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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.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2009.12a
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• pp.313-313
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• 2009

지속 가능한 농업과 안전한 농산물의 생산을 유지시키면서 환경부담 물질 투입량을 절감시킬 수 있는 농법을 개발하기 위해서 유기농자재 사용실태 및 효과를 조사했다. 전북 익산시 웅포면 유기농업 시범마을 현지 농가에서 사용 중인 유기 농자재의 실태를 조사하고 또한 유기농자재의 성분을 분석하였다. 유기농 자재 시용효과를 검증하기 위해서 시범마을 현지 농가포장에서 삼광벼 품종으로 포트 육묘 후 기계이앙을 실시하고 유기농자재를 시용하여 조사하였다. 유기농업 종합기술 시범마을에서 활용중인 유기농자재는 27.5%가 유기농 목록에 공시된 자재를 사용하고 있었다. 시범마을에서 활용중인 유기농자재의 성분 중 수분은 평균 50.1%, 유기물함량은 36.0%, 총 질소함량은 1.71% 이며 염분은 0.56% 이였다. 경종방법과 유기농자재를 이용하여 새로운 유기농 벼 재배 기술을 개발할 목적으로 시험포를 조성한 지역에서 토양의 화학성분을 조사한 결과 pH, 마그네슘, 규산은 망성 단지에서 낮은 경향을 보였고, 유기물, 인산, 규산, 칼륨은 삼기단지에서 높았다. 포트육묘 후 이앙을 실시한 결과 단위면적당 이앙주수별 생육에서 재식밀도가 높을 수록 초장과 경수가 적었다. 산파육묘와 포트육묘 이앙 모두 도복 발생은 없었으며, 포트 육묘 3절의 두께가 양호하였다. 쌀겨 시용에서 잡초발 생량이 적었으며, 포트육묘 이앙에서 병해충이 적었다. 수량은 산파육묘에 비해 포트육묘 방식에서 5~10% 높았는데, 포트 육묘에서 주당 수수, 수당 립수가 많았고, 천립중이 무거웠다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.617-623
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• 2001

To predict the seasonal variation of dissolved oxygen (DO) in Hakata bay, Japan, possible 20 time-series of different hourly-solar-radiation intensities were generated based on stochastically changing solar radiation intensity, and a numerical simulation on dissolved oxygen (DO) was carried out for each time series by using the Sediment-Water Ecological Model (SWEM). The model, consisting of two sub-models with hydrodynamic and biological models, simulates the circulation process of nutrient between water column and sediment, such as nutrient regeneration from sediments as well as ecological structures on the growth of phytoplankton and zooplankton, The results of the model calibration followed the seasonal variation of observed water quality well, and generated cumulative-frequency-distribution (CFD) curves of daily solar radiation agreed well with observed ones, The simulation results indicated that the exchange of sea water would have a great influence on the DO concentration, and that the concentration could change more than 1 mg/L in a day. This prediction method seems to be an effective way to examine a solution to minimize fishery damage when DO is depleted.