Water disinfection by photodynamic inactivation with cationic porphyrin

In recent years, the application of porphyrin derivatives in photodynamic inactivation (PDI) is arousing great interest in water disinfection process studies. As an alternative to other disinfection techniques traditionally used (chlorination, ozonolysis, irradiation with UV light), the photooxidation process is a promising technology characterized by low cost, low environmental impact and easy management. In this work basic experimental tests about the application of organic expanded porphyrins in water disinfection by photodynamic inactivation (PDI) technique are depicted. The photoinactivation properties of a positive charged porphyrin, namely 5,10,15,20-Tetrakis (1- methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate) (TMPyP), were tested in water disinfection, using S.aureus and E.coli. Data showed that TMPyP treatment on 107 CFU/ml bacterial culture was effective at nanomolar concentration and in a very short treatment time (15 minutes). By 1 hour of 50 W/m2 irradiation, a maximum of 99,99989 % abatement on S.aureus and a maximum of 99,995 % abatement on E.coli, using respectively a dosage of 0,5 mM and 5 mM TMPyP, were obtained. TMPyP effectiveness was tested even on waste water and the preliminary results demonstrated that, even if wild bacteria are generally more resistant to the treatment, photo-oxidation is a promising technique to refine water disinfection processes.