Abstract
In Hiyoshi Reservoir (Kyoto Prefecture, Japan), two submergible aerators were installed in 1997 and have been used for the elimination of the anaerobic layer in the deep reservoir. In 2009, one of these aerators was modified as a trial, to circulate water in the shallow layer of the reservoir, so as to release spent air (oxygen-poor air) from the top of the aerator into the shallow layer. As a performance evaluation test, a field study of shallow layer circulation was conducted during the summer in 2010, under the condition of a strong thermocline existing at a depth of around 5 m. In the field test, water temperature distribution was measured within a 20 m radius around the aerator and at water depths of 0 to 20 m, during both the operation and idling of the aerator. Secondly, the velocity distribution of radial flow was measured around the aerator to clarify the water entrainment due to the air plume. As a result, it was confirmed that the thermocline was destroyed within a 10-13 m radius during operation, a horizontal cold flow (intrusion) was observed at the depth of the bottom, a cold dome resulted from thermocline destruction, and a newly developed air parcel shredder enhanced the water entrainment effect.
