Acher, A.J., Institute of Soils and Water, The Volcani Center, Bet Dagan, Israel
Elgavish, A., Department of Isotopes, The Weizmann Institute of Science, Rehovot, Israel

A new method for the destruction of algae in surface waters by dye-sensitized photooxidation is described. The algae (Peridinium, Pediastrum and Cosmarium) used as test organisms were inoculated in an artificial culture medium, containing a dye-sensitizer, with subsequent incubation in a controlled environment (20 ± 2°C, 14 h light, 10 h darkness). Water samples from Peridinium bloom in Lake Kinneret underwent similar treatment. The algicidal effect of various sensitizer concentrations and of different sunlight exposure times was investigated. Complete destruction of algae was obtained in about 2 weeks of incubation after exposure to solar radiation for 30-60 min in the presence of 0.25, 0.15 and 0.75 mg 1-1 methylene blue or 0.5, 0.8 and 0.8 mg 1-1 rose bengal in Peridinium, Pediastrum and Cosmarium cultures, respectively. © 1980.