The efficiency of solar disinfection for the inactivation of Total Coliforms (TC) and Escherichia coli (EC) in drinking water was tested in two pilot studies performed in rural communities of the States of Chihuahua and Oaxaca, Mexico. The solar disinfection of drinking water (or photodisinfection) is an inexpensive alternative for easy application in rural communities. The study zones were selected mainly because they lack formal water supply systems and the population is forced to consume untreated water directly from rivers and shallow or artesian wells. The efficiency of the water disinfection process based on solar energy was determined in the dry and rainy seasons with water from the most contaminated sources in the study zones. The performed tests consisted of studying the effect of disinfecting water by direct exposure to sunlight during the whole day, with and without solar concentrators, in plastic bottles of commercial beverages. The three types of bottles used were transparent, partially painted black (one half of the bottle, along the longitudinal axis), and totally black. The study shows that, in these geographic zones, the available water must be disinfected before consumption, and disinfection efficiency can reach 100% through the use of solar radiation.

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