• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.547-551
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• 1998

Reaeration coefficient is the physical absorption of oxygen from the atmosphere by water. It is the most important natural means by which a stream replaces the oxygen consumed in the biodegradation of organic wastes, and the rate constant describing this process is the reaeration coefficient, It. Reaeration coefficient is the dominant parameter affecting the use of water quality model. Therefore accurate estimation of the reaeration coefficient is essential for optimum water quality management. There is several method to estimate stream reaeration coefficient. In this study, it would be concluded that SI-peak method is of practical use when applied to small stream, and CRI method is adequate to large stream.

• Water for future
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• v.21 no.3
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• pp.281-290
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• 1988

As the aeration is one of the most important roles for the purification of polluted water, aquatic aerobic microorganism makes use of aerated dissolved oxygen to decompose the pollutant and purify water. In this study, a reactor was operated in a laboratory to examine the effects of salinity and rainfall on reaeration and then a model was proposed to estimate the reaeration coefficient. From the results of the experiments, the reaeration coefficient, $k_2$($day^{-1}$), can be expressed by $k_2=k_{2f}+3.98667{\times}10^{-2}{\cdot}C+4.88437{\times}10^{-1}{\cdot}r\;where\;k_{2f}$ : the reaeration coefficient in the fresh water at $20{\circ}C,\;(day^{-1})$ C: chloride concentration, ($g/{\ell}$), r:rainfall intensity,(mm/hr) Accordingly, it is concluded that the rate of reaeration is proportional to the chloride concentration and rainfall intensity. Also, it is known that the rainfall intensity contributes to the overall oxygen balance in a body of water more significantly than the salinity.

• Journal of the Korean GEO-environmental Society
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• v.15 no.8
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• pp.45-50
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• 2014

The microorganism decomposition experiment of sewage in the underground sewer has the limit of experiment condition and time. The way to reproduce the microorganism decomposition in the underground sewer was studied using batch reactor setting up the DO as a limiting condition. The DO concentration in the sewer is controlled by reaeration. It is possible to obtain correlation between flow condition and reaeration coefficient through the reproduction of reaeration phenomenon by controlling the flow condition in the sewer using this phenomenon. And it is possible to set the flow condition and agitation intensity (velocity gradient) that has the same reaeration coefficient using the correlation between the reaeration coefficient with the flow condition and reaeration coefficient with the agitation intensity. The circumstances in the sewer system was reproduced using batch reactor setting up the DO as a limiting condition from these results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.4
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• pp.57-65
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• 1999

A modified gas tracer method was used to obtain reaeration coefficient from an artificial channel and a reach of Bokha stream, Ichon city. Propane was used as the tracer gas and Rhodamine-B dye as a dispersion and dulution tracer. Concentrations of propane in water sample were measured using a gas chromatograph and concentrationsof dye using UV-Spectrophotometer. To compare measured values with predicted values,commonly used 14 equations were selected . Results of this study suggested that the modified gas tracer method is a potentially useful procedure for th edetermination of reaeration cofficients. However, estimated reaeration coefficients from predictive equations were significantly different from that of this study. Therefore, when using predictive equations, careful selection of equation with consideration for hydraulic characteristics such as flow depth and average velocity, or use of newly derived predictive equation which is adequate for questioned stream would be needed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.4
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• pp.155-167
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• 1996

동일한 하천의 용전산소량(DO)을 예측하는 경우에도 사용하는 재포기계수$(K^2)$는 계산하는 공식에 따라 커다란 차이를 나타매며, 부적합한 공식의 사용에 의한 $(K^2)$의 계산은 하천의 수질관리 정책결정에 지장을 초래하므로 현장사정에 적합한 공식의 개발이 필요하다. 이러한 공식의 개발은 많은 현장측정 자료를 사용하도록 신뢰성이 높으나 현장측정은 소요되는 비용에 제약을 받기 때문에 신뢰성과 경제성을 동시에 고려한 표본의 크기의 적정규모를 산정하는 것이 필요하다. 본 연구에서는 Monte Carlo 방법에 의해 통계적으로 수출된 $(K^2)$를 사용해서, 주어진 자료에 의해 개발된 공식을 사용할 때 야기되는 오차가 $(K^2)$개수의 증가에 따라 얼마나 감소하는지를 널리 사용되는 공식 중에 Owen공식과 Churchill공식을 New Jersey에 있는 Passaic River에 적용시켜 검토하였다. 표본의 크기가 10에서 20으로 증가할 때 오차가 크게 감소하였으며 20을 넘어 증가시켰을 때에는 오차의 감소폭이 미미하였다. 초차의 감호형태와 단위측정당 소요되는 비용을 고려할 때 약 20정도의 표본의 크기가 적정수준의 규모에 판단된다. 이러한 적용사례의 결과는 회귀모델의 이론적 계산결과에 의한 오차 감소와 흡사하여 본 연구결과는 여러 가지(K2)공식과 광범위한 하천의 조건에 적용이 가능할 것이며, 본 연구에서 사용한 적정표본의 크기 산정방법은 회귀분석에 의해 실험식을 개발하는 다른 분야에도 적용이 가능하다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.97-103
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• 1997

DO concentration in the aquatic system is important for the water quality management perspective. Water quality model uses available reaeration coefficient (K2) estimation equations in calculating DO, however, they might include inevitable uncertainty that the model output can be less reliable. In this study, the calibrated QUAL2E model for the Passaic River in New Jersey, U.S., was used to examine the effect of K2 estimation equation on the output DO concentration of the river. The model was run with six commonly used equations separately with all the other conditions remained same. The result showed that the output DO concentration profiles varied widely with different equations, and maximum difference was 4.96 mg/L for the same location which is unacceptably large. It implies that the development of reliable equation is required for proper water quality management. The unreliable model output can lead to a wrong decision in water quality management such as unnecessarily high or too low treatment of wastewater, which will cause serious effect on the community economically and socially in either case. Generating more reliable model output with slight investment to develop a site specific K$_2$ equation can improve the decision making process significantly and is highly recommended.

• Water for future
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• v.17 no.2
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• pp.85-97
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• 1984

Measuring the river flow and water quality in the midstream of the Nakdong River, the natural purification status in examined through the analyses of the elements which affect the variation of dissolved oxygen, and DO model is evaluated to the midstream reach of the river. The major results of this study are as follows; the pruification factor of the of the river is relatively high, it is worried over eutrophication considering much production of algae, and it is evaluated that important factor affecting the DO value computed by the proposed DO model are in order of reaeration coefficient, carbonaceous BOD and deoxygenation constant.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.595-601
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• 2005

In this research, effects of water circulation on phosphorus release from sediment into water body were studied. Sediments sampled at the Daechung Lake were used for the column experiments with circulation and non-circulation conditions. Deaeration coefficient, $K_1$ and reaeration coefficient, $K_2$ of non-circulation condition were 0.133 and 0, respectively, while $K_1$ and $K_2$ for circulation condition were 0.46 and 0.018, respectively. Oxidation Reduction Potential (ORP) showed a linear relationship with dissolved oxygen (DO) when DO is over 2 mg/L. Phosphorus concentration induced by phosphorus release from sediment was highly dependent upon DO, ORP, and pH. Under anaerobic condition, phosphorus release rate was higher for $Fe^{2+}$-bounded phosphorus compared to that of $Ca^{2+}$-bounded phosphorus.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.780-780
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• 2012

하천에서의 1차원 수질해석에 널리 사용되는 QUAL2E 모형은 전체 대상구간을 요소(element)로 구성하고 다시 수리학적으로 유사한 흐름특성을 가진 구간(reach)으로 구분하고 있다. 각 구간에서는 동일한 유속과 수심이 형성되는 것으로 가정하고 있기 때문에 자연하도의 다양한 흐름변화, 특히 자연하천의 보나 낙차공으로 인한 국부적인 흐름상태를 모형에 반영하기 어려우며, 이로 인한 실제 흐름특성과의 차이는 수질모의 해석결과에도 다양한 영향을 미치게 된다. QUAL2E 모형에서는 이와 같은 보나 낙차공의 수리학적 특성을 반영하기 위해 댐 계수옵션이 있으며, 이를 통해 흐름으로 인한 폭기 현상을 재현하도록 되어 있다. 본 연구에서는 모형 내 재폭기 계수에 대한 민감도 검토를 수행하였으며, 한강의 팔당댐부터 한강대교까지를 대상구간으로 잠실수중보로 인해 발생하는 재폭기 현상에 관해 연구하였다. 본 연구는 보나 낙차공이 있는 하천에 대해 QUAL2E 모형을 적용할 경우 용존산소(DO)를 비롯한 여러 가지 수질변수의 정확도 높은 예측에 기여할 것으로 기대된다.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.331-339
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• 2006

This research was carried out to understand the impacts of thickness of sand capping to control phosphorus release from sediment into overlying water. As capping effectively retards release flux, phosphorus concentration in water body can be maintained if phosphorus release rate was kept under microbial degradation rate. With capping thickness increases, deaeration rate become less, while reaeration coefficient become higher. Phosphorus release rate and capping thickness were linearly correlated. The results of regression analysis indicated that phosphorus release can be controlled effectively by sand capping of least 20${\sim}$40 mm thickness.