The Effectiveness of Eliminating Malathion from Water by Ultraviolet Irradiation

Organophosphorus pesticides are one of the most consumable poisons in the country. Such poisons can enter water sources by different routes; since consuming some drinking water which contains an amount of poison higher than the standard level, causes undesirable effects to human health and hygiene. The purpose of the present work is to study the effectiveness of eliminating malathion from water by ultraviolet irradiation (UV) mercury lamp with a medium pressure. In this experimental study, concentrations of 0.5, 1, and 2 mg/L and pH values of 6, 7, and 9 from malathion poison were irradiated at the times of 10, 20, 30, 40, 50, and 60 minutes in a ultraviolet reactor. The amounts of malathion poison were determined by HPLC instrument and then compared before and after the irradiation. The results of the present study at different concentrations, times and pH show that the minimum reduction of malathion occurs at the time period of 10 min (%46) and the maximum reduction at the time period of 60 min (%87.25) (p<0.05). Also, the effectiveness of irradiation process decreases (from 93 to 87.25%) with increasing the poison concentration (from 0.5 to 2mg/L) (p<0.001). On the other hand, the efficiency of the process increases with pH increase. The present study shows that applying UV irradiation for 60 min. with the concentration of 0.5 mg/l and pH=9, has the most effectiveness on reducing malathion poison content of water. Therefore, the application of UV reactors could be considered as an appropriate method for the treatment of waters contaminated with these poisons.