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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/m² ). 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. [ABSTRACT FROM AUTHOR]

Background and Objectives: Free living nematodes due to their active movement and resistance to chlorination; don't remove in conventional water treatment processes thus can be entered to distribution systems and cause adverse health effects. UV irradiation can be used as a method of inactivating these organisms. Materials and Methods: This study is done to investigate the effect of ultraviolet lamp on inactivation of free living nematode (Rhabitidae) in water. The effects of duration of irradiation, turbidity, temperature, UV dose and pH are investigated in this study. Ultraviolet lamp used in this study was all watt lamp with intensity of 24 µw / cm². Results: Contact time required to achieve 100% efficiency for larvae nematodes and adults were 9 and 10 minutes, respectively. Increase of turbidity up to 25 NTU decreased inactivation efficiency of larvae and adult nematodes from 100% to 66% and 100% to 64%, respectively. Change in pH ranged from 6 to 9 did not affect the efficiency of inactivation. With increasing temperature inactivation rate increased. Conclusion: The results showed that there was a significant correlation between the increase in contact time, temperature rise and turbidity reduction with inactivation efficiency of lamp( p<0.001). Also the effect of the lamp on inactivation of larvae nematode was more than the adults. [ABSTRACT FROM AUTHOR]