Efficiency of sulfate radicals produced by solar photo-activated on bacterial inactivation

In this study, the effect of sulfate (and hydroxyl) radicals produced by solar light and solar light on the inactivation of E. coli and P. aeruginosa bacteria was investigated. In order to generate sulfate radicals, K2S2O8, Na2S2O8 and Oxone at three different concentrations (0,05-0,1-0,2 mM) were used as persulfate source. The inactivation coefficients (k1 and k2) of the removal processes were obtained using the GInaFiT (Geeraerd and Van Impe Inactivation Fitting Tool) modeling tool. After the inactivation processes, it was determined whether there was a re-growth in both bacteria and the cost of the processes was calculated. With the addition of persulfates to the inactivation process using solar light, there was an increase in the removal of E. coli and P. aeruginosa. The increase in oxidant concentration in Solar+K2S2O8, Solar+Na2S2O8 and Solar+Oxone processes increased bacteria removal and the highest inactivation was obtained with Oxone at each concentration. In general, in all inactivation processes, P. aeruginosa was more resistant than E. coli and required longer inactivation times. Different inactivation models were tested using the GInaFiT modeling tool and it was seen that the Biphasic model was suitable for both bacteria. In the inactivation coefficients obtained according to the biphasic model, the k1 values were found to be higher than the k2 values, and the coefficients increased with the increase in concentration. In regrowth experiments, greater cell damage was observed with the addition of persulfate salts, in contrast to inactivation by solar light. The Solar+Oxone processes cause more chemical costs, but also shorten the inactivation time, and therefore it has been determined that it causes less energy cost. As a result, it has been determined that sulfate radicals produced by solar light activation are effective in bacterial inactivation.