An In-Situ Experiment on Oxygen Solubility of Micro-Bubble Aeration
in A Eutrophic Dam-Reservoir
https://search.jcold.or.jp/icold/symposium/2012/2012.14.pdf
https://youtube.com/shorts/aiTP8quyCaw
In a dam-reservoir with long hydraulic retention time, density field tends
to be thermally stratified and the hypolimnion becomes
anoxic due to eutrophication. In such anoxic water, nutrients, ionic metals,
dissolved organic matters, etc. are significantly released
and high amount of hydrogen sulfide and methane are also generated from
sediments by biochemical reduction. In order to
minimize such environmental hazards, oxygen needs to be artificially supplied
into the hypolimnion with some aeration equipments.
Micro bubble aeration is one of promising techniques to efficiently feed oxygen
to the anoxic water. In this study an in-situ
experiment on micro-bubble aeration was carried out in a eutrophic reservoir
by using two types of aerator. The experiment was
started early summer when the hypolimnion was completely anoxic and the
reservoir was thermally stratified with a sharp
thermocline. The aeration system was intermittently operated by monitoring
dissolved oxygen so that DO concentration was kept in
a suitable range of concentration. The aeration was continued until the reservoir
being uniformly mixed by fall overturn. A field
measurement of temperature, dissolved oxygen and water quality was performed
during the experiment. Performance of the two
types of aeration systems was examined by evaluating oxygen capacity transfer coefficients.
In this study oxygen micro-bubble aeration was carried
out in order to operate a high-performance aeration
system with minimum energy. In the in-situ experiment
in a dam-reservoir, two types of aerators were tested.
Test I is to directly inject micro-bubbles to the
hypolimnetic water and Test II is to feed the
liquid-oxygen mixture that is produced by an aerator
equipped in the pipe. Through measurements of
thermal stratification and water quality, it was confirmed
that the anoxic water polluted with heavy metals and
nutrients was very well purified by the proposed aeration
system. In order to compare performance of the two
systems, oxygen capacity transfer coefficients were
evaluated from the time-dependent DO concentration.
Test II shows a better performance of oxygen transfer
than Test I. It is expected that the present aeration
system would be a powerful engineering tool as a
countermeasure against water quality troubles
