3 フェロー会員 山口大学大学院 理工学研究科(〒755-8611 山口県宇部市常盤台2-16-1) 4 正会員 山口大学大学院 理工学研究科(〒755-8611 山口県宇部市常盤台2-16-1) 5 正会員 宇部工業高等専門学校 物質工学科(〒755-8555 山口県宇部市常盤台2-12-1) 6 非会員 (有)バブルタンク(〒755-0808 山口県宇部市西平原4-10-30) 7 非会員 (株)日本港湾コンサルタント(〒141-0031 東京都品川区西五反田8-3-6 TK五反田ビル) 8 非会員 宇部工業高等専門学校 技術室(〒755-8555 山口県宇部市常盤台2-12-1) 湖沼や海域の水質改善，特にDO改善を目的として著者らが開発中の液膜式気体溶解技術の概要を述べ， そのDO改善性能に関する室内実験の結果を検討する．本方式は，処理対象水を気泡液膜の構成要素にし て液相中の気体濃度の勾配を大きくすることにより気体溶解を効率的に行う．また管内の浅い部分で曝気 してエアリフト効果を利用して深部の水のDO改善を行うため稼働に必要なエネルギーが小さい．室内実 験の結果から装置内にハニカムを装着することの影響を評価した．また，酸素溶解能力およびエネルギー 効率の最適条件について調べ，管内径に対して最適の空気流量があること，h型管の水平部の水面からの 高さを抑える方が有利であること，エネルギー効率は空気流量が小さいほど有利であることなどを明らか にした．

The ability of a gas dissolving device to improve the DO condition of water is evaluated using the oxygen transfer rate. Usually the oxygen transfer rate is measured in mixing-type treatment, where air bubbles are released in the water tank. This method, however, has some disadvantages, such as that it cannot be used for compressed-type gas dissolving devices and that it requires the evaluation of the overall gas transfer coefficient. The present study proposes a convenient method of evaluating the oxygen transfer rate which is applicable to gas dissolving devices of both compressed and pressure-free types, applicable to water with an arbitrary DO concentration, and does not require the evaluation of the overall gas transfer coefficient. Evaluation of DO improvement is done using the equivalent DO increment, devised to eliminate the influence of the DO concentration of the water before treatment. The value of the oxygen transfer rate is represented as the value at a temperature of 20 degrees Celsius. Laboratory experiments to check the method have shown that the proposed method of measurement is valid.

No abstract

Oxygen deficiency in closed waters seems to induce serious problems. The authors have been trying to solve the problem utilizing liquid membranes of bubbles cluster formed by aeration in the h-shaped pipe located near the water surface, which enables to improve DO condition in the water at high efficiency and low energy cost. In this paper experimental results are given for DO improvement of the above system. The oxygen transfer rate N (20) and the efficiency E P defined as the transfer rate per unit work rate required for aeration are examined for various values of the aeration depth H A , flow rate of supplied air Q g , and the height of the pipe H U . As the results, both N (20) and E P take high values when H U is small and H A is large. Also there is some optimum Q g for a given diameter of the pipe.