OPERATIONAL VERIFICATION OF OXYGENATION DEVICE DUE TO ANAEROBIC LAYER IMPROVEMENT IN SALT-FRESH DOUBLE-LAYERED BRACKISH LAKE

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 anaerobic salt water layer, we installed the oxygen dissolving device (WEP) in the actual waters. The effect of oxygenation was confirmed at approximately 210,000 m² during the two-month operation of the device. On the other hand, it was confirmed that the amount of residual dissolved oxygen depended on the operating time of device and the concentration of hydrogen sulfide, and that the water mass movement and the supplied dissolved oxygen were important. In addition, it was confirmed that the durability of the device casing would be damaged in water in a strongly reduced state within about two years. In case of installation conditions for this paper, it becomes clear that operating costs, maintenance and repair costs every two years are required, and annual maintenance costs of 3.9 to 5.5 million yen are required. From this result, water quality of anaerobic brackish waters could be improved by dissolved oxygen supply. However, it was suggested that the operation with limited capacity such as isolated water pools was advantageous for actually installation.