Development of bubble-less ozonation and membrane filtration process for the treatment of contaminated water

Abstract

The aim of this research was the evaluation of performance efficiency of a continuous treatment process, integrating bubbles-less ozonation and membrane filtration for water purification. A new bench-scale experimental apparatus was designed, comprising of two ceramic membrane modules, connected in series. In the first module, bubble-free ozone contacting takes place via a modified α-Al2O3 membrane. Chemical modification of a-Al2O3 membranes was performed with four different modifying solutions in order to change their hydrophilic behavior and thus, to reduce membrane resistance to ozone transfer. The hydrophobic character of initial and modified membranes was examined by contact angle measurements. The results showed that the chemical modification of membranes decreased the hydrophilic character of the original membranes and in certain cases transform them to hydrophobic. The values of measured contact angles were between 76° and 143°. In the second treatment module (in series), a microfiltration or ultrafiltration ceramic membrane was placed in order to separate suspended particles, macromolecules and/or arsenic. The hybrid process was evaluated for the treatment of aqueous solutions, contaminated by humic acid, kaolin (clay) and/or arsenic. The results indicated that the combination of ozone with membrane filtration limits fouling (around 25%) and improves the removal of arsenic (up to 80% removal), although it had no effect on TOC reduction.