A novel combined solar pasteurizer/TiO₂ continuous-flow reactor for decontamination and disinfection of drinking...

A new combined solar plant including an annular continuous-flow compound parabolic collector (CPC) reactor and a pasteurization system was designed, built, and tested for simultaneous drinking water disinfection and chemical decontamination. The plant did not use pumps and had no electricity costs. First, water continuously flowed through the CPC reactor and then entered the pasteurizer. The temperature and water flow from the plant effluent were controlled by a thermostatic valve located at the pasteurizer outlet that opened at 80 °C. The pasteurization process was simulated by studying the effect of heat treatment on the death kinetic parameters (D and z values) of Escherichia coli K12 (CECT 4624). 99.1% bacteria photo-inactivation was reached in the TiO₂-CPC system (0.60 mg cm^-2 TiO₂), and chemical decontamination in terms of antipyrine degradation increased with increasing residence time in the TiO₂-CPC system, reaching 70% degradation. The generation of hydroxyl radicals (between 100 and 400 nmol L^-1) was a key factor in the CPC system efficiency. Total thermal bacteria inactivation was attained after pasteurization in all cases. Chemical degradation and bacterial photo-inactivation in the TiO₂-CPC system were improved with the addition of 150 mg L^-1 of H₂O₂, which generated approximately 2000-2300 nmol L^-1 of HO^● radicals. Finally, chemical degradation and bacterial photo-inactivation kinetic modelling in the annular CPC photoreactor were evaluated. The effect of the superficial liquid velocity on the overall rate constant was also studied. Both antipyrine degradation and E. coli photo-inactivation were found to be controlled by the catalyst surface reaction rate.