Bubbleless membrane contactor for enhanced ozone mass transfer and ozonation for water purification

Abstract

Membrane contactor, a physical barrier separating two phases to introduce gas into aqueous solutions through the bubbleless process, has gained considerable development for its improved gas transfer and contaminant removal efficiencies for water purification. However, a comprehensive assessment of a contactor with liquid flowing on the shell side and gaseous ozone flowing on the lumen side is scarce for ozonation. Therefore, we have developed a membrane contactor equipped with commercial hydrophobic polytetrafluoroethylene (PTFE) hollow fibers and investigated theoretically and experimentally the interaction between ozone and solution. Mass transfer behavior was evaluated by comparing experimental value and computational model of corresponding coefficients. Phenol was then selected as a model contaminant to evaluate the treatment performance of membrane contactors in ozonation. Crucial operating conditions involving the gas/liquid flow rate, concentrations of ozone and phenol, pH and geometry of fibers were assessed for their impacts on both ozone mass transfer and pollutant degradation. The results showed that the membrane presented high chemical resistance to ozone and could achieve stable mass transfer through bubbleless aeration. Under the optimum operating conditions, the overall liquid mass transfer coefficient was 1.12 × 10−5 m/s. The percentage removal and mineralization of phenol with 30 min hydraulic retention time could reach ∼100 % and 21.1 %, respectively, which have demonstrated the high treatment efficiency of the membrane contactor as an alternative technique in water purification.