Photocatalytic materials in water disinfection

It has been estimated that 1.2 billion people lack access to safe drinking water around the world resulting not only on the prevalence of waterborne diseases but also threatening the economic development. Water resources management is critical, mainly in regions with low rainfall and growing population. The lack of access to safe drinking water has become a main concern usually related with poverty since 1.5 million children die yearly as a result of waterborne diseases. In Mexico, waterborne diseases affect 6 % of the total population with rural communities as the most affected anytime; 22 % of the population does not has access to piped water (CNA 2011). This situation, however, is not limited to Mexico but common in other developing countries. In order to deal with the generation of safe drinking water, several different water disinfection processes have been developed. Free chlorine and its derivatives are currently the most widely used disinfecting reagent capable to inactivate pathogenic species in drinking water. However, it is also well known that free chlorine reacts with organic matter present in surface or underground water to generate disinfection by-products (DBPs) reported as human carcinogens. Within the variety of disinfection technologies, advanced oxidation processes (AOPs) have emerged as efficient and cost-effective for pathogen inactivation in water. Specifically, heterogeneous photocatalysis (HPC) is the AOP with the widest variety of technological applications resulting in its ability to inactivate nuisance microorganisms. The use of metal-based semiconductors as photocatalyst for water disinfection has been widely reported demonstrating being effective for the inactivation of several microorganisms and carcinogen cells. From the economic point of view, the possibility of using solar energy to drive HPC processes may be considered as an interesting alternative for use in developing countries to assure access to safe drinking water. The application of these technologies to water disinfection using solar radiation, coined as enhanced photocatalytic solar disinfection, has allowed the efficient inactivation of highly resistant microorganisms. The aim of this chapter is reviewing the state of the art in the application of HPC processes with TiO and some new semiconductor materials for inactivation of waterborne pathogens, discussing its advantages and potential limitations as well as analyzing challenges and opportunities for its application at real scale in regions with lack of access to safe drinking water.