The present study aimed to improve the solar water disinfection by the photosensitization of coumarin extracts of some plants of the Rutaceae family (Citrus reticulata, Citrus aurantium and Citrus maxima). The results found in this work show an inhibition of around 7% of faecal coliforms after 15 minutes of exposure for solar disinfection. An inhibition of 17 % is noticed after 30 minutes of exposure. On the other hand, for water treated and exposed to the sun, an inhibition of around 90% is noticed for all the extracts after 30 minutes of exposure. Complete inhibition is recorded after 60 minutes of exposure. These results show that the plant extracts used improve significantly the solar disinfection of water. The photosensitizing activity observed in these extracts is due to the presence of coumarins. These molecules, in the presence of light, absorb 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 microorganisms present in the water.
The present study has consisted to the disinfection of water by photosensitization with 5-methoxypsoralen fixed on polystyrene (MOP-5-P). The results obtained in this study show the complete inhibition of fecal coliforms after six minutes of irradiation (365 nm). But the system (MOP-5-P) loses its activity after the application because of the formation of 5-MOP photodimers on the surface of polystyrene (2, 2-cycloaddition). Irradiation at a wavelength below 320 nm allows the regeneration activity of MOP-5-P system. This shows that these photodimers formed on the surface of polystyrene are reversible and depend on wavelength irradiation. This reversibility is demonstrated by the regeneration activity of the system after irradiation at 254 nm.
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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