Effect of hydrogen peroxide on bacillus subtilis spore removal in an electrophotocatalytic system

Bacillus subtilis spores have been widely used in UV reactor validation as a possible surrogate for protozoa studies. UV light has become one of the most important methods of water disinfection. Hydrogen peroxide has been used as a strong oxidizing agent. The rate of disinfection of hydrogen peroxide is enhanced by UV and ozone. Bacillus subtilis spores are not sensitive to H2O2; thus, they have been the most important targets of peroxide sterilization. The goal of this study was to evaluate the potential of an electrophotocatalytic/ hydrogen peroxide reactor for spore inactivation by studying this method with Bacillus subtilis spores. Contaminated water in an electrophotocatalytic reactor was prepared by adding 10 ²-10 ³ spores of B. subtilis to the water. The batch electrophotocatalytic reactor was a 360-ml glass vessel. The characteristics of the electrodes were as follows: An electrode of ZnO nanoparticles immobilized on zinc and a copper electrode. The studied variables were pH (6-8), the number of spore suspensions (10 ²-10 ³ spores / ml), the light emitting diodes (LED) UV-A lamps (2-4 W), time (5-40 min), layers of zinc oxide nanoparticles (1-3), the concentration of hydrogen peroxide (0.1-1000 mM), and voltage (10-20 V). The findings show that using H ₂O ₂ in the presence of UV-A irradiation (UV/H ₂0 ₂) leads to an increase in spore removal efficiency. Optimal removal was obtained at pH 7, with a time of electrolysis of 5 minutes, 2 layers of nano ZnO, and a voltage of 10 V. This result suggests that this method is efficient for the enhanced disinfection of water.