Inactivation of Escherichia coli and Enterococci in urban wastewater by sunlight/PAA and sunlight/H2O2 processes

Two solar driven Advanced Oxidation Processes (AOPs), namely sunlight/H2O2 and sunlight/peracetic acid (PAA), were investigated for the inactivation of two bacterial families (Escherichia coli and Enterococci) in real urban wastewater. Preliminary lab scale experiments were performed by using a solar simulator in order to evaluate the proper initial dose of H2O2 and PAA, respectively. According to the results achieved, 50 and 100 mg L−1 of H2O2 and 4 and 8 mg L−1 of PAA were chosen for the subsequent pilot scale experiments in a Compound Parabolic Collector (CPC) based reactor. The sunlight/PAA process resulted in a higher inactivation rate (3.52 log units of E. coli and 4.50 log units of Enterococci with an initial dose of 8 mg PAA L−1) compared to sunlight/H2O2 process (3.13 log units of E. coli and 2.45 log units of Enterococci with an initial dose of 100 mg H2O2 L−1) after 120 min of solar irradiation (7.42 kJ L−1 cumulative energy per unit of volume). It is noteworthy that significantly lower initial doses of PAA allowed to achieve a higher inactivation rate compared to H2O2, which makes sunlight/PAA an attractive option for wastewater disinfection in small communities.