The study of improvement of solar water disinfection by photosensitization with coumarin extracts of some plants of Rutaceae family (Citrus limonum, Citrus paradisi and Citrus sinensis) shows an inhibition of 90% for fecal coliforms after 30 minutes of sunshine. Complete inhibition is noted after 60 minutes. In water not treated and exposed to the sunlight, an inhibition of 32% was noticed after 60 minutes. The photosensitizing activity noted in these extracts is due to the presence of coumarins. These molecules in presence of light absorb the energy and pass from the ground state to the excited state. Returning to the ground state, the stored energy is transferred to the oxygen, which then passes from the ground state, triplet, to the excited state, singlet, and inhibits the coliforms present in water.
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