Membrane defouling using microbubbles generated by fluidic oscillation

Abstract

Abstract Impurities and colloidal substances are two of many fouling conditions that reduce the membrane filtration performance used in wastewater treatment. This study investigates the potential of fluidic-oscillation-generated microbubbles (MBs) to defoul the filtration membrane. Cartridge filters for microfiltration (MF) of 1 μm pore size were fouled using surface seawater collected from the Hull coastal area. The seawater was circulated at 5.8 L/min to actuate colloidal substance deposition on the membrane surface. The recorded feed channel pressure drop (ΔP) across the membrane filters showed rapid fouling occurred in the first 8 hrs of the circulation. Fluctuations of ΔP during the next 8 hrs were observed showing the colloids filling the pores of the membrane, and remaining steady for 2 hrs showing the membrane was completely fouled. The filtration membrane was cleaned and defouled using fluidic-oscillator-generated MBs. The fouled membranes were sparged with 1 L/min of air scouring for ∼1 to ∼2 hrs to remove the deposited colloids and impurities on the surface of the membrane. The membrane, analysed by Scanning Electron Microscopy (SEM), UV254 and Electrical Conductivity (EC) meter, showed the extent of MBs-mediated removal of the deposited colloidal particle from the membrane surfaces. This study found that the highest defouling rate occurs with MBs generated by fluidic oscillator (closed vent), followed by MBs generated by fluidic oscillator (opened vent) and MBs generated without fluidic oscillator at 9.53, 6.22, and 3.41 mbar/min, respectively.