Solar disinfection as a direct tertiary treatment of a wastewater plant using a photochemical-photovoltaic hybrid system

Abstract This work evaluates the SolWat hybrid system for solar water disinfection and photovoltaic energy generation, for its implementation in tertiary treatment plants, using real wastewater directly from the effluent after its secondary treatment. Solar disinfection of E. coli, Enterococcus faecalis and Clostridium perfringens microorganisms was evaluated over the course of a complete year. Four experiments in batch mode were conducted in autumn, winter, spring and summer, and microbiological and physicochemical parameters were analysed. In addition, the kinetics of solar disinfection during 4 h were analysed, and the dose of lethal ultraviolet radiation for microorganisms established. Results showed that E. coli, Enterococcus faecalis and C. perfringens did not complete total bacterial inactivation after 4 h of treatment in the SolWat system, but that the inactivation levels achieved were sufficient as to allow for the reuse of water for various uses (urban, agricultural, industrial, etc.). Clostridium perfringens continued to be the most resistant bacteria vs. E. coli and Enterococcus faecalis. The total photovoltaic energy production in the hybrid system compared to the reference system was the same, generating both the SolWat module and the reference module identical electrical power due to the compensating effect of module water cooling vs. radiation losses.