• 한국환경과학회지
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• 제4권3호
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• pp.107-107
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• 1995

This study was conducted to evaluate the effects of pressure and dissolved oxygen concentration on the activated slut비e and to determine the optimum depth of deep shaft process. Some results from this study were summarized as follows. 1. It is considered that low sludge product in the activated sludge system maintaining high dissolved oxygen concentration is attributed to the increase of endogeneous respiration rate caused by the increase of aerobic zone in the sludge floe. 2. The increase of dissolved oxygen concentration does not affect to the increase of organic removal efficiency greatly and therefore the limiting factor is the substrate transfer into the inner part of floe. 3. The yield coefficient, Y is decreased in proportion to the increase of oxygen concentration. In this study, Y values arre ranged from 0.70 to 0.41 according to the variation of dissolved oxygen concentration from 18.0mg/$\ell$ to 258 mg/$\ell$. 4. The optimum depth of deep shaft process should be determined within the limits of non-toxicity to the microorganism and it is about loom in this study.

• 수산해양기술연구
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• 제59권4호
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• pp.387-398
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• 2023

Conventional aquaculture faces declining productivity, shifting to recirculating aquaculture system (RAS), known for minimizing water usage and maintaining consistent water temperatures for year-round fish growth. Rainbow trout (Oncorhynchus mykiss), a globally important cold-water species and the third most farmed fish in inland waters of Korea, valued for its fecundity and rapid growth. Dissolved oxygen, an important environmental factor affecting fish production and economics, highlights the need for smart aquaculture practices. Since 2018, the rise of intelligent aquaculture platforms, incorporating information and communications technology (ICT), emphasizes the essential role of RAS implementation. This eight-week study aimed to determine the optimal dissolved oxygen concentration for rainbow trout in RAS, utilizing a device for continuous monitoring, control and record. Dissolved oxygen concentrations were set at 5-6 mg/L, 9-10 mg/L, 14-15 mg/L and 17-18 mg/L. The growth rate significantly decreased at 5-6 mg/L, with no significant differences in other experimental groups. In hematological analysis, growth hormone (GH) was significantly highest at 5-6 mg/L, followed by 9-10 mg/L while Insulin-like growth factor-1 (IGF-1) was significantly lowest at 5-6 mg/L. In conclusion, the optimal dissolved oxygen concentration for rainbow trout in RAS is approximately 9-10 mg/L. Higher concentrations do not contribute to further growth or profitability.

• 한국환경과학회지
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• 제11권1호
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• pp.85-91
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• 2002

The effects of initial concentration of dissolved oxygen content, Cu(II) and EDTA in an aqueous Cu(II)-EDTA solution on $TiO_2$ photo-oxidation of EDTA were investigated using $TiO_2$ (Degussa P-25) and UV irradiation at $20{\circ}C$. In the presence of dissolved oxygen and/or Cu(II) the photo-oxidation rates of EDTA were enhanced. The rates linearly increased in the range of initial Cu(II) concentration below 1.79 mM, while abode this concentration those were kept constant. The trend or the EDTA photo-oxidation rates appeared to be akin to the Langmuir-Hinshelwood equation farm and the k values calculated were 0.05 mM/min for the free-EDTA system, and 0.17 mM/min far the Cu(II)-EDTA system. These meant the aqueous EDTA decomposition was enhanced due to weakening of the intra-molecular bond strength of EDTA by complexation with Cu(II) added. It was concluded the decomposition of aqueous EDTA by $TiO_2$ photo-oxidation was maximum in the presence of dissolved oxygen supplied by air purging and of Cu(II) with its concentration for 1:1 Cu(II)-EDTA complexation ratio.

• 융합신호처리학회논문지
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• 제9권3호
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• pp.219-223
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• 2008

스크린 프린트법으로 저가형 후막 용존산소 센서를 제작하고, 휴대용 용존산소 측정 시스템을 구현하였다. 전류 특성은 인가전압(바이어스 전압)을 0.7 V로 하였을 때, 응답시간도 짧고 전류 값의 변화도 가장 크다는 것을 알 수 있었다. 시스템의 구현은 MCU, 증폭단, 필터단, 전원부 및 디스플레이로 구성하였다. 용존산소 농도는 아날로그 값을 디지털로 변환하여 백분율로 표현되도록 프로그램하였다. 제작된 용존산소 측정 시스템은 표준 용액 대비 오차 ${\pm}0.5%$의 정확도 및 약 100초의 응답시간을 나타내어 고가의 상용 용존산소 센서를 대치할 수 있을 것으로 기대된다.

• 한국환경보건학회지
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• 제12권2호
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• pp.11-15
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• 1986

Hydroxlamine effect on the determination of dissolved oxygen by the azide-modified Winkder method and polarography has been studied. It was found that hydroxylamine interference on the dissolved oxygen by the azide-modified Winklet method can be eliminated completely by using permanganate. An inexpensive and convenient polarograph device was constructed. Dissolved oxygen in an air-saturated 0.1 F KCl solution undergoes, independent of hydroxylamine concentrations a two-step irreversible reduction at the dropping electrode the $H_2O_2$ produced in the first step is reduced to $H_2$O in the second. Two waves of equal size result, the first with a half-wave potential (E1/2) at about -0.13 V and the second at about -0.91 V (vs. SCE).

• 대한지리학회지
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• 제48권3호
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• pp.336-347
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• 2013

This paper presents an evaluation of stream restoration projects in Seoul with a focus on dissolved oxygen. Five test sites across four streams were measured for dissolved oxygen (DO) in late May to early June in 2012 and compared against a set of minimum and maximum thresholds. Only one test site, Hwarang-cheon, showed measurements below 6 mg/l DO. Towards the upper limit, the Hwarangcheon site was the only tested stream which was not at risk of DO supersaturation. The Danghyeon-cheon site had the highest probability of supersaturation, with DO saturation exceeding 130% expected 86.5% of the time. When measured every hour during daytime, DO levels showed diurnal variations, peaking in the afternoon. However, they showed inconsistent results along transects of the streams. Overall, the streams are rich in DO. To maintain the streams in good standing, nutrient loading should be addressed to prevent potential algal bloom induced hypoxic events down the line.

• 한국환경과학회지
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• 제25권7호
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• pp.927-935
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• 2016

Dissolved oxygen is necessary for many biological processes as well as many industrial practices. Dissolved oxygen released from water in dissolved air flotation (DAF) systems can be have many different applications. However, DAF systems are very costly to operate. To develop more efficient DAF systems, a deeper understanding of the process of oxygen being released from water is required. In this study, molecular dynamics (MD) simulations were used to simulate 100 oxygen molecules surrounded by 31002 water molecules at temperatures ranging from $0^{\circ}C$ to $100^{\circ}C$. Simulations were carried out for 10 ns, during which, in most cases, all the oxygen molecules were released from the water droplet. With MD simulations, visualization of the molecules escaping the water droplet was possible, which aided the understanding of the interactions between molecules at the nano-scale. The results showed that as the oxygen molecules moved near the edge of the water droplet that the oxygen molecules hesitated before escaping the water droplet or returned to the interior of the water droplet. This was because of the attractive forces between the water and oxygen molecules. Moreover, after most of the oxygen molecules were released from the droplet, some were found to return to the droplet's edge or even the interior of the droplet. It was also confirmed that oxygen molecules were released at a faster rate at higher temperatures.

• Ocean and Polar Research
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• 제32권4호
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• pp.439-448
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• 2010

CTD를 이용하여 용존산소의 농도에 대한 연속적인 관측이 이루어지면서 용존산소 농도 분포의 fine structure에 대한 연구가 가능해졌다. 뿐만 아니라 altimeter로부터 해저 퇴적물 표면에 최대한 가까이 까지 관측이 가능해짐에 따라 해저 경계면에서의 용존산소 농도 분포에 대한 정보를 얻을 수 있게 되었다. 지금까지 동해 울릉분지의 용존 산소 농도의 수직 분포는 동해 북부의 일본 분지와는 수심 300 m 이하에서는 수심에 따라 지속적으로 감소하는 형태를 보이는 것으로 알려져 있다. 그러나 2005년부터 2006년까지 6회에 걸쳐 수심이 1000 m보다 깊은 지역에서 해저퇴적물 상부 100 m 이내의 수심까지 용존산소를 관측한 결과, 울릉분지 내의 용존 산소 농도의 수직분포형태는 3가지로 분류된다. 첫 번째는 지금까지 알려진 바와 같이 수심에 따라 지속적으로 감소하는 형태(Type-1), 두 번째는 Type-1과 같은 형태를 보이다가 해저 경계면 근처에서 급격히 산소의 농도가 줄어드는 형태(Type-2), 세 번째는 해저 경계면 상층에 용존산소 농도의 최소층이 존재하는 형태(Type-3)이다. 울릉분지 수심 1000 m 이상되는 지역에서는 분지 전반에 걸쳐 Type-2 형태로 분포하고 Ulleung Interplane Gap을 포함하여 일본 분지와 가까운 지역에서는 Type-1, 독도 인근 해역에서는 Type-3 형태의 분포를 보인다. 표층 퇴적물에서 유기물 분해를 전제로 해저 경계면의 용존 산소 분포를 이용하여 계산된 표층 퇴적물의 산소 소모율은 $0.2{\sim}5.8\;mmol\;m^{-2}d^{-1}$로 실제 퇴적물 배양을 통해 얻은 산소 소모율 약 $1{\sim}9\;mmol\;m^{-2}d^{-1}$(정 등 2009; 이 등 2010b)와 일치하는 것으로 미루어 볼 때, 울릉분지의 전반에 걸쳐 Type-2와 같은 형태의 분포를 보이는 것은 울릉분지의 표층 퇴적물에서 높은 농도를 보이는 유기물의 분해가 일차적으로 중요한 역할을 하는 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제31권6호
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• pp.541-547
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• 1999

Corrosion control, in the end-shield cooling system of Wolsung Nuclear Power Plant, is directly related to the control of dissolved oxygen (DO). The current method, being used to deoxygenate the end-shield cooling water, is a chemical treatment by addition of reducing agent, hydrazine, to react with DO. This method has several limitations including high reaction temperature of hydrazine , unwanted explosive hydrogen gas production, and its intrinsic harmful property. A new approach to remove DO using a membrane-based oxygen removal system (MORS) was tried to overcome limitations of the hydrazine treatment. The DO removal efficiency of the MORS was found to be in the range 87% to 98%: The higher vacuum, the lower water flow rate and the higher water temperature tend to increase the DO removal efficiency.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.419-420
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• 2010