Assessment of solar water disinfection enhancement with H2O2 and dissolved oxygen on inactivating different waterborne pathogens

Water scarcity has been growing for the last decades and one feasible solution for water-deprived areas is the storage and treatment of roof-harvested rainwater. Solar disinfection (SODIS) is a proven water treatment procedure, but several drawbacks still need assessing, such as increasing the output volume of treated water, reducing the treatment time and/or increasing the inactivation efficiency performance. In this study, the addition of low concentrations (1-5 mg/L) of H2O2 and/or the increment of dissolved oxygen (DO) has been tested at a pilot plant scale using a solar Compound Parabolic Collector photo-reactor with the aim of enhancing the disinfection efficiency of SODIS. Their performance has been assessed against a consortium of five pathogens normally found in rainwater: E. coli, E. faecalis, S. enteritidis, P. aeruginosa and MS2 bacteriophage. The addition of DO and/or H2O2 to solar photo-inactivation (SP-I) proved to enhance pathogens' inactivation kinetics. Results have shown that O-2 supply affects E. coli, P, aeruginosa and E. faecalis as their kinetic constants increase 1.48, 1.17 and 1.6 times, respectively. On the other hand, H2O2 addition enhances the inactivation of all pathogens. being the most noteworthy MS2 inactivation as > 5 Log Reduction Values (LRV) were reduced for all concentrations between 99% and 95% of the energy required for SP-I. Finally, the combination of both agents is also effective but can only be noted in E. faecalis inactivation, which is better than with only H2O2 addition. The findings obtained in this study show that from the perspective of implementing solar technologies in the field, the addition of DO sparging can be discarded due to a slightly enhanced disinfection performance, while the use of low H2O2 concentrations can be envisaged due to both, the enhancement of the disinfection performance and the competitive cost estimated (0.0025 /L) in comparison with only SODIS (0.002 /L).

Automated summary

The addition of low concentrations of H2O2 and/or increased dissolved oxygen has been tested to enhance the disinfection efficiency of solar disinfection (SODIS) for roof-harvested rainwater. Results show that both methods can improve pathogen inactivation, with H2O2 having a more significant effect on all pathogens and dissolved oxygen primarily affecting E. coli, P. aeruginosa, and E. faecalis.