VERIFICATION OF ANEAROBIC LAYER IMPROVEMENT IN BRACKISH LAKE BY CONTINUOUS OPERATION OF OXYGENATION DEVICE INCLUDING FREEZING SEASON

Abstract

 Experimental study was carried out in Lake Abashiri where is brackish lake with double-layered formation of freshwater and saltwater. In order to reduce anearobic salt water layer, we installed the oxygen dissolving device (WEP) in the actual waters. As a result of continuously operating the device from icecover period to after snow melting, the flow in the lake was suppressed under the ice, and the rise of dissolved oxygen and the increase of turbidity due to the oxidation of hydrogen sulfide were confirmed in the vicinity of the device. The effect of oxyganation was recognized in the area about 90,000 m² during the two-month operation of the device under the ice. The hydrogen sulfide concentration was confirmed to decreace significantly around the oxygen supply elevation. However, the hydrogen sulfide did not become zero. On the other hand, the flow in the lake was restarted after the snow melt, it was confirmed that the dissolved oxygen and the turbidity were decreased because the oxygen supply effect flowed away with ice break. From the results of water quality analysis, the oxygenation by WEP confirmed hydrogen sulfide around the device reduced by 40%. And also reduced total phosphorus and total nitrogen by 20%. it was found that the water quality of the brackish anaerobic layer can be improved by the dissolved oxygen supply, and the effect becomes clearer as water bodies stagnated.