Bacillus subtilis spore inactivation in water using photo-assisted Fenton reaction


Sustain. Environ. Res., 21(5), 285-290 (2011)



Erick R. Bandala, Roberto Pérez, Angel Eduardo Velez Lee, Jose Luis Sanchez-Salas, Marco A. Quiroz and Miguel A. Méndez-Rojas


Bacillus subtilis, spores, water disinfection, photo-assisted Fenton, disinfection kinetics


Inactivation of Bacillus subtilis spores, considered among the most resistant microorganisms, was achieved using a photo-assisted Fenton reaction. Several different Fenton reagent concentrations were tested in combination with UV-A radiation (max = 365 nm) for the spore inactivation determined by measurements of spore viability. Best spore inactivation conditions were found using [Fe(II)] = 2.5 mM and [H2O2 ] = 100 mM and UV-A radiation. Under these conditions, over 9-log inactivation was reached after 20 min of reaction. Interesting results were also observed for experiments carried out for low Fe(II) concentrations or even when no Fe(II) was added and only H2O2 and UV-A radiation was used to evaluate microorganism inactivation. In the last cases, a lag phase was observed during earlier stages of the disinfection process and much lower spore viability was determined after longer irradiation times. The effect of ionic strength and natural organic matter (NOM) was also tested in the spore inactivation kinetic. It was noticed that important differences occurred as a result of variation in the solution ionic strength as well as from the presence of NOM. In both cases, an important decrease on the inactivation rate was observed. Experimental data fitted fairly well using a modification of the delayed Chick-Watson inactivation kinetics and the values of the rate constant used to perform an objective comparison among the different experimental assessment were carried out. We conclude that the photo-assisted Fenton reaction is a good method to inactivate one of the most resistant microorganisms and can be used to inactivate other pathogens like Anthrax and other waterborne diseases vectors. The efficiency of this method depends on the quality of the raw water. If a cost-effective process is desired, the proposed technology should be coupled with pre-treatment with conventional drinking water processes.


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