using ultraviolet irradiation for removal of malathion pesticide in water

background: organophosphorus pesticides are one of the most consumable poisons. such poisons can enter water sources by different routes. since consuming some drinking water containing an amount of poison higher than the standard level, causes undesirable effects on human health. this research aimed to study the effectiveness of elimi­nating malathion from water by ultraviolet irradiation (uv) mercury lamp with a medium pressure. methods: in this experimental- applied study, variants of initial phs and initial concentrations and exposure times were investigated. initial concentrations of malathion were 0.5, 1 and 2 mg/l. the samples were then exposed to uv irradiation interruptedly the time periods of 10, 20, 30, 40, 50 and 60 minutes. the uv lamp used in the reactor was medium pressure (irradiation intensity= 200 w/m 2 ). the amounts of malathion were determined before and after the irradiation by hplc instrument. moreover, the results obtained from the study were analyzed using spss software and anova and t -test statistical trials. results: the minimum reduction occurs at 10 min (%46) and the maximum reduction in 60 min (% 87.25) ( p < 0.05). in addition, the effectiveness of irradiation process decreases with increasing the poison concentration ( p < 0.001). however, the efficiency of the process increases with ph increase. conclusion: the results show the most effectiveness were achieved at 60 min and 0.5 mg/l and ph= 9. therefore, the application of uv reactors could be considered as an appropriate method.