Inactivation of bacteria by sulfate radicals

In this study, the inactivation effect of sulfate radicals activated by UV-A radiation and alkaline medium on E. coli and P. aeruginosa bacteria was investigated. K2S2O8, Na2S2O8 and Oxone were used to obtain sulfate radicals. The effects of two different doses (2 and 3 mmol/L) of K2S2O8, Na2S2O8 and Oxone activated by UV-A radiation were studied. 0,25, 0,5, 0,75 and 1,5 mmol/L NaOH were used together with K2S2O8 to obtain the sulfate radical in the alkaline activated persulfate process. Inactivation coefficients (k) were obtained with the help of GInaFiT (Geeraerd and Van Impe Inactivation Fitting Tool) using the inactivation curves obtained in the experiments. The effect of three different sulphate salts activated by UV-A radiation on bacterial inactivation was investigated and it was revealed that sulfate radicals formed as a result of activation with UV-A radiation increase bacterial inactivation by approximately 1,3 log. In addition, the highest bacterial inactivation among three different sulfate salts was seen in the UV-A + Oxone process. Increasing NaOH concentration in alkaline medium activation caused an increase in bacterial inactivation. It was also found that bacterial inactivation increased when the initial sulfate salt dose was high. It was found that the reaction of E. coli and P. aeruginosa to disinfection processes was different in both disinfection processes used and that P. aeruginosa was more resistant than E. coli bacteria. Different mathematical models (included in Microsoft® Excel add-in utility GInaFiT) were tested to fit experimental inactivation data. In general, it has been determined that the Biphasic model is suitable for the inactivation results of two microorganisms in all disinfection processes. It was observed that the formation of sulfate radical increased the inactivation coefficient according to inactivation coefficients determined by the biphasic model were examined As a result, it has been concluded that sulfate radicals are effective in the inactivation of the tested bacteria, and that sulfate salts activated by different methods can be an alternative method for water disinfection.