Effects of experimental conditions on E. coli survival during solar photocatalytic water disinfection

Results of photocatalytic disinfection of Escherichia coli K12 in water in a compound parabolic collector (CPC) solar reactor are reported. The aim of the study is to quantify the influence of operating parameters, such as flow rate, water quality and bacterial concentration, on bacterial viability in solar photocatalysis and in the dark. The catalyst used was an industrial titanium-dioxide-coated paper matrix fixed on a tubular support in the focus of the CPC. Addition of TiO2 notably improved solar-only disinfection up to 6 logs disinfection in 90 min. Between 10 and 2 L/min, photocatalytic disinfection effectiveness tended to increase with decreasing flow rates.In dark experiments, inactivation of 99% of viable E. coli cells in distilled water was detected after 90 min of recirculation at 10 L/min in the CPC reactor. A detailed study of bacterial viability in the solar reactor in the dark was therefore performed, varying flow rates, initial concentrations and osmolarity. It was found that bacterial viability in the reactor strongly depends on all the parameters examined, so that disinfection and dark inactivation overlap when working under low-osmolarity conditions and low bacterial concentrations.