**3.1 Introduction**

344 Mass Transfer - Advanced Aspects

Due to the superior oxygen supply efficiency, even if the aeration depth is as low as less than 1 m, a sufficient amount of oxygen can still be provided. In contrast, the conventional aeration tank necessitates a depth of 4-5 m to achieve a commensurate oxygen supply.

Although some energy is consumed as a consequence of the friction between the airlift tube wall of LFFA and surrounding water body, we suggest that this portion of energy consumption is far below the wasted energy in the conventional aeration system. Moreover, the energy wasted in the traditional aeration system can be re-used for the oxygen supply. Therefore, this novel LFAS-based method definitely opens an energy-efficient pathway to

Profile Planform

Fig. 3. Lab-scale LFFA

Fig. 4. The picture of forming liquid film

improve the oxygen transfer efficiency.

LFAS possesses the following characteristics.

Therefore, LFAS is a very energy-saving aeration system.

In order to evaluate the oxygen transfer performance of the LFFA, under the experimental conditions of different bubble diameters and different aeration amounts, comparative experiments are conducted on a liquid-film aeration system and conventional aeration system by respectively using de-oxygenated water and activated sludge.
