• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.163-171
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• 2001

Reaeration phenomena, the physical process of absorption of oxygen from atmosphere, is one of the important parameters of dissolved oxygen simulation in streams. This study was aimed at predicting reaeration coefficients in rural small streams, examining the influence of drop structure on reaeration and the seasonal fluctuation of reaeration coefficients. Reaeration coefficients of five streams including four tributaries of Bokha watershed in Gyeonggi Ichon and Onyang stream in Chungnam Onyang were measured. Constant rate injection (CRI) method using propane and Rhodamine-WT as gas and dye tracer was adopted. Reaeration coefficients ranged between 6.16 and 29.16 reciprocal day, higher than those in USGS database. Prediction equation,$k_2=CV^{0.593}$, was regressed from the measured data at 95% confidence level, with an absolute error of 21.2% and a standard error of 4.0 reciprocal days. Reaeration coefficients of experimental reaches with drop structure showed percentile increases of 42.3 to 159.2 compared to those without it, an indication that drop structure plays an important role on stream reaeration. Taking into consideration the seasonal fluctuation of reaeration coefficients, the values measured during September and October were the highest, mainly due to the removal of aquatic plants. by intensive rainfall during summer.

• 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.

• 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.

• 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.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.570-577
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• 2000

In this study, using modified tracer method(Constant Rate Injection, CRI method), reaeration rates were measured in the territories of Bokha stream. In case of Kwanri stream, reaeration rates of a diversion were measured simultaneously. Propane gas and Rhodamine-WT were used as gas and dye tracer, respectively. The experimental results show that reaeration rates of the stream were ranged from 6.16 to 24.52 1/day and those of a diversion in Kwanri stream were ranged from 28.39 to 123.61 1/day. It is resulted that mean velocity of stream is a dominant factor in reaeration process and diversion significantly influence on reareation process.

• 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.

• Journal of Korea Water Resources Association
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• v.35 no.5
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• pp.511-523
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• 2002

In order to develop the weir with high reaeration efficiency, the reaeration experiments at linear weir, ogee spillway type weir, and labyrinth weirs were conducted and the results were compared. The effect of roughened crest was also analyzed. It was found from the experiments that the oxygen transfer efficiency at the ogee spillway type weir was the lowest and that at the linear weir was second lowest among the weirs used in the experiments. It was also revealed that the reaeration efficiencies of the labyrinth weirs increase as the included angles become smaller. The roughened crest which causes the disintegration of overflow was found to increase the reaeration efficiency significantly. On the basis of the results of the experiments, the pilot construction of the labyrinth welt with included angle of 30 degree was made. The labyrinth weir was made up by assembling the frame and then filling the ripraps into the frame. The ripraps were exposed at the crest to split the overflow. The average value of oxygen transfer efficiency observed at the pilot weir was 0.18. It is expected that the results from the experimental study and the field data of the pilot weir would serve for the improvement of water quality by the weirs with high reaeration efficiency.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.574-575
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• 2005

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.428-433
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• 2009

Dissolved oxygen is considered as one of the important water-quality constituents in streams from one century ago and fishes perish in low dissolved oxygen concentration. Environmental scientists and engineers have introduced the deterministic model to estimate dissolved oxygen concentration of streams and recommended the use of the Delta Method (DM), Approximate Delta Method (ADM), Extreme Value Method (EVM) and Optimization Method (OPT) which can be applied in no spatial variation of dissolved oxygen. The diurnal or annual variation of dissolved oxygen is mainly determined from the parameters such as reaeration rate, 1st production rate and respiration rate which are related to dissolved oxygen. Each method was briefly introduced and applied to two sampling sites of Anseong Stream watershed in this paper. The limitation, advantages and disadvantages of each method were reviewed and analyzed after running the each method. From these analyses, the benefit-cost approach to estimate dissolved oxygen effectively in streams was recommended.

• 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.