Flotation is successfully applied in various processes, such as galvanic
tailings purification, washing and lubricating liquids treatment, oil/water emulsions
separation, etc. An interesting implementation appears to be using flotation as
pretreatment in membrane separations. The prospective engineering approach for
contaminated wastewaters treatment is combined membrane-electroflotation
process.Membrane-electroflotation is a complex physico-chemical process taking place
in “liquid-gas-solid” system, based on the hydrodynamic phenomena of gas-liquid
streams. In case of membrane flotation the dependence of gas content on
bubbling rate has been determined. There are two areas of dependence—at low
gas content (5-17%), area I and at higher gas content (17-29%), area II. Based on
the value of single bubble emersion rate calculated for every measured bubble
diameter, an average volumetric single and group bubble emersion rate in
membrane flotation was determined. In electroflotation the average radius of
hydrogen bubbles increases from 20 microns to 90 microns depending on module’
height; and stationary distribution of bubbles is achieved upon 1-4 min. Hydrogen
bubbles content versus the process time is characterized by the time of retard. At the
same time the oxygen appears in electroflotation unit at the very beginning of the
process without any retard time. Increase of hydrogen bubbles residence time in the
upper sections of electroflotation module leads to rise of average radius and decrease of
bubbles containing from 0.00525 to 0.00109.
Keywords: Wastewater treatment, flotation, membrane-electroflotation, gas
content, flotocomplex, bubbles flow rate, experimental characterization
