(UNESCO / Japan Young Researchers' fellowships programme)

Domestic wastewater treatment by biological aerated filter - power consumption optimization by renewable energy supply

Summary of research carried out: 
Domestic wastewater treatment by biological aerated filter - power consumption optimization by renewable energy supply

The multi scale experimental study is aimed at : (i) studying in global scale the effect of variation of physic chemical quality of liquid phase on hydrodynamics and mass transfer in biofilters, (ii) studying hydrodynamics and mass transfer close to the packing and investigate bubbles/packing contact by visualization techniques.

In order to understand who much physic chemical quality of liquid phase can influence mass transfer efficiencies in biofilters, hydrodynamic and mass transfer parameters have been investigated for different liquid phase containing clean water and some additives (Salts, sugar, suspended solids and varied pH and Glycerol) that can be encountered in industry, those compounds have been putted in a three phase fixed bed reactor operating in batch mode using two kinds of packing thoroughly studied by Maldonado et al.,(2008).

For each liquid phase tested, hydrodynamics parameters have been determined. Gas hold up, pressure drop, slips velocities and bubbles sizes have been calculated. For each configuration, volumetric mass transfer coefficient has been measured under different superficial gas (air) velocities. Global scale experiments were carried out in a cylindrical PVC column of 4.5 m of height and 0.15 m of diameter at laboratory temperature and atmospheric pressure. Air was injected at the bottom of the column using a porous disc diffuser. The superficial gas velocity range from 2.3 10-3m.s-1 to 2.9 10-3 m.s-1.

For all cases, an increase was observed in hydrodynamics with increasing superficial gas velocity and with all of compounds added on the liquid phase. Mass transfer coefficient decrease with all of compounds tested except with lower concentrations of salts and acidic and basic. Local scale experiments were performed in a packed bed quasi Two-dimensional cell made of Plexiglas with 200 mm of height, width of 100 mm and thickness of 3 mm to investigate the visualization of mass transfer and hydrodynamic in axial profile of bubble, assessing through fixed bed, high speed and color camera was used for visualization experiments using an oxygen sensitive dye (Resazurine) that have pink color with presence of oxygen for visualizing oxygen transfer and kalliroscope for visualizing bubbles hydrodynamics.

Abderrahmane Kherbeche, 03/08/2012