Inactivation of Escherichia coli in fresh water with advanced oxidation processes based on the combination of O-3, H2O2, and TiO2. Kinetic modeling

摘要

The purpose of this work was to study the efficiency of different treatments, based on the combination of O-3, H2O2, and TiO2, on fresh surface water samples fortified with wild strains of Escherichia coli. Moreover, an exhaustive assessment of the influence of the different agents involved in the treatment has been carried out by kinetic modeling of Escherichia coli inactivation results. The treatments studied were (i) ozonation (O-3), (ii) the peroxone system (O-3/0.04 mM H2O2), (iii) catalytic ozonation (O-3/1 g/L TiO2), and (iv) a combined treatment of O-3/1 g/L TiO2/0.04 mM H2O2. It was observed that the peroxone system achieved the highest levels of inactivation of Escherichia coli, around 6.80 log after 10 min of contact time. Catalytic ozonation also obtained high levels of inactivation in a short period of time, reaching 6.22 log in 10 min. Both treatments, the peroxone system (O-3/H2O2) and catalytic ozonation (O-3/TiO2), produced a higher inactivation rate of Escherichia coli than ozonation (4.97 log after 10 min). While the combination of ozone with hydrogen peroxide or titanium dioxide thus produces an increase in the inactivation yield of Escherichia coli regarding ozonation, the O-3/TiO2/H2O2 combination did not enhance the inactivation results. The fitting of experimental values to the corresponding equations through nonlinear regression techniques was carried out with Microsoft(R) Excel GInaFiT software. The inactivation results of Escherichia coli did not respond to linear functions, and it was necessary to use mathematical models able to describe certain deviations in the bacterial inactivation processes. In this case, the inactivation results fit with mathematical models based on the hypothesis that the bacteria population is divided into two different subgroups with different degrees of resistance to treatments, for instance biphasic and biphasic with shoulder models.