Solar Photocatalytic Disinfection of Water
It is estimated that there are 748 million people throughout the world without access to improved water sources for drinking and many more rely on water that is not safe to drink due to contamination with pathogenic microorganisms. Furthermore, the reuse of wastewater is becoming increasingly important due to water scarcity throughout the globe, and it is vitally important to ensure that water for reuse is free from pathogenic microorganisms. Solar energy is free and ubiquitous on the Earth's surface. The combination of solar disinfection and photocatalysis technology offers real possibilities for removing lethal pathogenic microorganisms from polluted water and drinking water. The treatment time taken for the solar disinfection of drinking water can be greatly reduced by utilizing heterogeneous photocatalysis. This chapter reviews and compares the fundamental mechanisms of solar and solar photocatalytic inactivation of microorganisms. The complexity of the mechanisms, involving reactive oxygen species and their effects on the cell wall, membrane and internal components of microorganism, are discussed. Furthermore, the photocatalytic inactivation of antibiotic resistant bacteria is discussed. The development of visible light active photocatalytic materials for solar disinfection is reviewed and, finally, there is a short discussion concerning photo-reactors specifically for the solar photocatalytic disinfection of water.