**5.2 Experimental conditions and methods**

By means of a recycling liquid-film apparatus (4 cm in each individual airlift pipe diameter, 1 cm in effective height, 12.56 cm2 in cross-sectional area of the airlift part), liquid film aeration tests in a 53 cm deep, 80 L water tank with a surface area of 1510 cm2 are carried out

18 16 14 12 10 8 6 Air flow rate (L/min)

6 8 10 12 14 16 18 Air flow rate (L/min)

**5. Comparison of liquid film and conventional aeration systems in regard to** 

The performance of aeration apparatus is compared in terms of the kLa values of the liquid film and conventional aeration systems. Meanwhile, the effectiveness of LFFA is corroborated by calculating an important energy-saving index-oxygen transfer efficiency *EA* , which is defined as the ratio of DO content to aeration-supplying oxygen amount.

By means of a recycling liquid-film apparatus (4 cm in each individual airlift pipe diameter, 1 cm in effective height, 12.56 cm2 in cross-sectional area of the airlift part), liquid film aeration tests in a 53 cm deep, 80 L water tank with a surface area of 1510 cm2 are carried out

0

Fig. 28. E0 as a function of air flow rate

**5.2 Experimental conditions and methods** 

E (mg-O /L-Air)

2

0

**5.1 Introduction** 

**kLa** 

Fig. 27. DO saturation rate as a function of air flow rate

10

20

30

DO saturation rate (%)

40

50

by applying air flow rates of 6, 8, 12 and 12.8 L/min. As a control, under the otherwise identical experimental conditions, the conventional aeration test is also investigated in this study. The experimental apparatus is shown in Fig. 29.

Liquid-film-type aeration experiment Conventional aeration experiment

Fig. 29. The experimental apparatus diagrams of liquid-film aeration system and conventional aeration system
