Abstract:
The aim of this paper is the theoretic and experimental study of the hydrodynamics and mass transfer of the swarm of bubbles
generated by fine bubble diffusers (FBD) made from ceramics. Thus the hydrodynamic parameters of the dispersed air-water
system (pressure loss on FBD, bubble size distribution, global gas hold up) were experimentally determined. Regarding mass
transfer, the volumetric mass transfer coefficient Kla, standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE)
were also determined. The results showed that Kla increases with air flow rate and there is an optimum air flow rate (120?180 l/h)
that gives maximum aeration efficiency. The maximum value of SAE (4.25 kgO2/kWh) was obtained for Q = 150 l/h, in
homogeneous regime. Comparing the ceramic FBD with a sintered glass FBD issued that an increase of 35% of the mass transfer
can be obtained by using glass FBD. Still, SAE accomplished by the two types of FBD tested is in the range given by literature or
even greater.

Gabriela Oprina, Florentina Bunea, Irina Pincovschi, Lucian M?ndrea