Removal of the surfactant sodium dodecylbenzenesulphonate from water by simultaneous use of ozone and powdered activated carbon: Comparison with systems based on O 3 and O 3/H 2O 2

Abstract

A study was conducted on the efficacy of the system based on the simultaneous use of ozone and powdered activated carbon (PAC) in removing sodium dodecylbenzenesulphonate (SDBS) from drinking waters and on the influence of operational parameters (PAC dose, ozone dose and presence of radical scavengers [HCO 3 −]) on this process. Results obtained showed that low doses of PAC during SDBS ozonation markedly increased the rate of SDBS removal from the medium. These results are due to the combined effect of two processes: (i) SDBS adsorption on the activated carbon surface and (ii) transformation of the dissolved ozone into ·OH radicals. At higher ozone and PAC doses, there was a higher rate of SDBS removal from the medium. The presence of HCO 3 − in the medium reduced the SDBS removal rate of the O 3/PAC system. This finding confirms that the presence of PAC during SDBS ozonation favours ozone transformation into ·OH radicals. Comparison of the O 3/PAC system with systems based on the use of O 3 or O 3/H 2O 2 showed that the efficacy of the O 3/PAC system to remove SDBS is much greater than that of the traditional oxidation methods. Thus, in the first 5 min of treatment (usual hydraulic retention time), the percentage of SDBS removed was 18% and 30% for the O 3 and O 3/H 2O 2 systems, respectively, compared with 70% for the O 3/PAC system. SDBS ozonation in surface waters intended for human consumption demonstrated that the O 3/PAC approach is the most efficacious of the studied systems, considerably increasing the SDBS removal rate and also reducing the concentration of dissolved organic carbon. Therefore, the results of this study show that the system based on O 3/PAC is a highly attractive option for the treatment of drinking water.