**1. Introduction**

446 Solar Radiation

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311-X, Patras, Greece, pp. 175-234.

*Open Spaces*, vol. 1, Amourgis, S. (Ed.), Hellenic Open University, ISBN 960-538-

Around the world, it is estimated that 1.2 billion people have limited or no access to safe water for domestic use. As a result, the prevalence of water borne diseases affects not only the health of the inhabitants of these regions, but also their economic development (Gelover et al., 2006). It is clear that water resources management is becoming a critical issue worldwide, especially in regions with low rainfall and growing population (Bandala et al., 2010).

Just considering Africa, Latin America and the Caribbean, about one billion people have no access to safe water supplies resulting in serious human health effects, i.e. 1.5 million children died every year due to water borne diseases. Moreover, the lack of safe drinking water has been related to poverty and considerable limitations for sustainable development (Montgomery and Elimelech, 2007). In Mexico, for example, waterborne diseases affect over 6% of the total population, being rural communities with less than 2,500 inhabitants the most affected, since only 78% of this rural population has access to piped water (CONAGUA, 2011). Unfortunately, this situation is not limited to Mexico, but it is common in other developing countries in Latin America.

It is well known that human pathogens become sensitive to different environmental conditions once discharged into a water body. For example, some environmental conditions such as temperature and ultraviolet (UV) radiation are capable of inactivating waterborne pathogens. However, engineering processes are required if the goal is to assure the generation of safe drinking water for remote, poor, isolated regions in developing countries (Castillo-Ledezma et al., 2011).

Several different disinfecting processes have been tested in order to deactivate undesirable microorganisms in water. Within this variety of disinfectants, Advanced Oxidation Processes (AOPs) have been proven efficient and cost-effective for water treatment (Blanco et al., 2009). These physical-chemical processes have the potential of producing deep changes in the chemical structure of pollutants as a result of the action of hydroxyl radicals (HO•) (Orozco et al., 2008). Several scientific studies suggest that AOP's high efficiency is related to their thermodynamic viability and the increased rate of reaction produced by

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hydroxyl radicals. Among various AOPs, photocatalytic processes are very attractive for the mineralization (conversion to carbon dioxide, water, and other mineral species) of aqueous pollutants and inactivation of pathogenic microorganisms (Gelover et al., 1999; Bandala and Estrada, 2007; Bandala et al., 2007 & 2008). The use of AOPs for water disinfection, using solar radiation as the energy source, usually referred to as *enhanced photocatalytic solar disinfection* (ENPHOSODIS), has allowed the efficient deactivation of highly resistant microorganisms. Specifically, heterogeneous and homogeneous photocatalysis are the AOPs with the most technological applications because of their ability to remove organic pollutants and their capability to inactivate nuisance microorganisms. Regarding heterogeneous photocatalysis, the use of titanium dioxide (TiO2) as a catalyst has been widely tested and proven effective for deactivating several microorganisms as well as carcinogen cells (Dunlop et al., 2008; Rincon and Pulgarin, 2003; Reginfo et al., 2008; Castillo-Ledezma et al., 2011). In comparison with the heterogeneous arrangement, homogeneous processes also rely on the generation of hydroxyl radicals. Nevertheless, it has been proposed that other highly oxidant species could be involved in pollutant degradation and microorganisms deactivation. Fenton and Fenton-like processes are among the most widely studied methodologies (Bandala et al., 2009; Guisar et al., 2007; Bandala et al., 2011). From the economic point of view, the possibility of using solar energy to promote both homogeneous and heterogeneous photocatalytic processes is an interesting alternative to the use of these technologies in developing countries (Bandala et al., 2011; Blanco et al., 2007).

The aim of this chapter is to review the state-of-the-art in the use of solar driven Fenton-like processes for the deactivating waterborne pathogens. It also the goal of this work to discuss the advantages and potential limitations of these treatment processes while analyzing the challenges and opportunities for the application of such technologies at real scale in poor, isolated regions in developing countries with no access to safe drinking water.
