Field Observation and Evaluation of Destratification by Aeration Circulation in a Dam Reservoir

Abstract

The purpose of this research is to examine the operation technique of the aeration circulation device that suits a local situation by the observations of the water temperature, the direction and velocity of the wind, etc. in the stratified dam reservoir.As a result, it was shown that the intrusion position by the aeration circulation is influenced by the water temperature distribution. Moreover, the flows of water in this reservoir was shown to have received the influence of wind driven flow, inflow and outflow strongly. Therefore, it was suggested that affected area by aeration can be wider if the aeration circulation device was operated referring to the flow of the reservoir that was presumed by the observations.

An Attempt to Measure the Oxygen Transfer Rate of a Gas Dissolving Device in a Separate-Type Experiment

“…Firstly, we explain existing methods of measuring the oxygen transfer rate, N (20) , and the problem with these methods, and then describe the proposed method of measurement, which would be available for one-pass-type gas dissolving devices.…”

“…In this paper, we denote the oxygen transfer rate satisfying all three conditions as "N (20) ", emphasizing the water temperature of 20 [°C]. Though the more common of the gas dissolving devices to recover the oxygen dissolution condition of environmental water has been the non-one-pass type, recently various devices of the one-pass type with high performance have been proposed 4)~17) , and it is easily expected that one-pass-type devices will become popular in the near future.…”

“…Though the more common of the gas dissolving devices to recover the oxygen dissolution condition of environmental water has been the non-one-pass type, recently various devices of the one-pass type with high performance have been proposed 4)~17) , and it is easily expected that one-pass-type devices will become popular in the near future. On the other hand, as a problem of the method of measuring a device's performance in dissolving oxygen, existing methods of measuring the oxygen transfer rate, N (20) , have been restricted to the non-one-pass-type devices and the ordinary pressure one-pass-type devices, and it is difficult for existing methods to measure the oxygen dissolving performance of the compressed one-pass-type gas dissolving devices. For if we apply the existing method to high-pressure-type devices, a significant portion of the oxygen dissolved in compressed conditions will be released from the water as bubbles when the water is left in atmospheric pressure conditions.…”

“…In this situation, development of methods for measuring the oxygen transfer rate, N (20) , which would be available for one-pass-type gas dissolving devices working in both compressed and pressure-free conditions, is desired. In this paper we propose a method for measuring the oxygen transfer rate, satisfying the above desire, and then check the method's validity through a laboratory experiment.…”

“…In this paper we propose a method for measuring the oxygen transfer rate, satisfying the above desire, and then check the method's validity through a laboratory experiment. The proposed method for measuring the oxygen transfer rate, N (20) , does not require the evaluation of the overall gas transfer coefficient, K L a, and therefore does not require the repeated measurement of the DO concentration during the test, which shortens the test time.…”