Impact of gas bubbling and backflushing on fouling control and membrane cleaning

Membrane fouling is an inherited phenomenon in microfiltration membrane processes which significantly impairs the filtration efficiency. This makes membrane regeneration an integral part of the microfiltration systems and necessitates the need for effective membrane cleaning in order to maintain higher efficiencies of the separation process. Experiments were carried out to evaluate the potentials of air bubbling and backflushing for reducing membrane fouling and for improving the membrane cleaning efficiency. Commercial yeast was used as test suspension with 10 g/L concentration whereas microfiltration experiments were conducted through a submerged flat sheet microfiltration membrane with a nominal pore size of 0.2 μm. Membrane regeneration efficiency was evaluated for five different filtration methods. The experimental results of this study show that effect of air bubbling and backflushing on fouling control and membrane cleaning was synergetic. However backflushing proved to be more effective in controlling fouling and improving membrane cleaning efficiency. The combination of backflushing and air bubbling was found to be the most effective method for both membrane cleaning and fouling reduction as this technique caused 80% of the solids to be retained within the feed stream. This combination of two filtration techniques resulted in 268% permeate flux enhancement due to reduction of particle deposition on membrane surface and helped in improving membrane cleaning efficiency in which case membrane was regenerated up to 98.5% in a minimum time of 30 min.

Research Highlights
► There was an optimum air flow rate for control of fouling and improvement of permeate flux.
► Backflushing when combined with air bubbling resulted in 80% retention of solids in the feed stream.
► Membrane regeneration reached up to 98.5% with the hydrodynamic parameters without any detergent.
► Membrane cleaning time was reduced to only 30 minutes when backflushing was combined with air bubbling.