Development of solar water disinfection systems for large-scale public supply, state of the art, improvements and paths to the future – A systematic review

Solar drinking water treatment technologies are one of the most promising strategies to increase access to safe drinking water worldwide, as they are effective, affordable and sustainable. However, the development of affordable, high-performance solar water treatment systems applicable to large-scale public drinking water supply remains necessary. In this work, the state of the art in the development of solar water disinfection systems is systematically reviewed and a critical discussion is presented. Studies reporting high-performance solar water disinfection systems, or those capable of being upgraded for application in large-scale potable water supplies, were included. The solar disinfection systems described in the literature are of the SOPAS type (solar pasteurization), SODIS (solar disinfection by ultraviolet radiation) or mixed type (SOPAS + SODIS) and are based on concentrating or non-concentrating solar collectors. SOPAS + SODIS systems are more effective at microbial inactivation and, continuous flow or intermittent flow disinfection approaches in systems based on concentrating solar collectors or evacuated tubes are more productive. All systems reviewed can be improved, integrating or improving the concentration capacity of solar radiation, and increasing the efficiency of absorbers and/or reactors. Combining improved SOPAS and SODIS systems to develop mixed systems has been found to be one of the most important advances in the development of high performance systems. The integration of photovoltaic-powered artificial UV radiation disinfection technology as well as photothermal and photocatalytic materials into improved mixed solar disinfection systems needs to be explored. The performance of these systems needs to be evaluated in scenarios that simulate real large-scale water supply contexts.