Water disinfection using photo-Fenton: Effect of temperature on Enterococcus faecalis survival

The photo-Fenton process is a promising alternative to classical water disinfection treat- ments, although information in this regard is scarce due to its operational limitations. The effect of temperature (10, 20, 30 and 40 C) was studied on water disinfection using the photo-Fenton reaction at initial near neutral pH with resorcinol as a model of natural organic matter (NOM). Enterococcus faecalis, a Gram-positive microorganism, was selected as an indicator of wastewater faecal contamination. The individual effects of different vari- ables involved in this process (mechanical stress, UVA, H2O2, Fe2þ, H2O2/Fe2þ, UVA/Fe2þ, UVA/H2O2 and UVA/H2O2/Fe2þ) were determined. UVA and H2O2 led to a 2.5-log decrease individually and the combined effect of both variables managed to disinfect up to the detection limit (i.e. from a 5.5 to a 6-log reduction) over the same treatment time. Only by adding 10 mg L 1 of Fe2þ, the inactivation time was reduced from 120 min (H2O2/UVA) to 80 min (H2O2/UVA/Fe2þ; photo-Fenton) with 120 mg L 1 of H2O2. A higher disinfection result for E. faecalis was observed by increasing temperature according to the Arrhenius equation in the photo-Fenton process. The detection limit was not reached at 10 C and, to achieve the detection limit at 20, 30 and 40 C, 80, 65 and 40 min were needed, respectively. The decrease in treatment time is a key factor in applying the photo-Fenton disinfection process to a wastewater treatment plant.