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Performance evaluation of ultraviolet radiation and ozone disinfection for municipal secondary effluent reuse (Case study in Isfahan North wastewater treatment plant)

This study aimed to evaluate and compare the performance of wastewater disinfection systems using ultraviolet radiation (UV) and ozonation to improve the secondary effluent quality of Isfahan North wastewater treatment plant. Therefore, the filtered effluent by a pretreatment unit from microscreen drum filter type with a pore size of 20 μm entered the disinfection pilots containing medium pressure (MP) UV lamps and ozonation system as tertiary treatment. In this study, the irradiation dose of UV (430–3,680 mW/cm2), and injection dose (10–40 mg/L), and contact time (1–15 min) of ozonation were altered. The results showed that the total suspended solids were reduced by 61.27% at the maximum dose of UV radiation and 89.36% at the highest concentration and contact time with ozone. Though the turbidity and chemical oxygen demand were not reduced by UV, their maximum removal by ozone was 80.52% and 40.74%, respectively. The fecal and total coliform reduction at the maximum UV radiation was 3.82 and 3.79 log and at the highest concentration and contact time with ozone was 4.11 and 3.55 log, respectively. The results revealed that 300 W lamp with 40 s contact time and ozone dosage of 40 mg/L and the contact time of 15 min could meet the fecal coliform criteria recommended by the guidelines of the environmental protection agency for some uses, such as irrigation of restricted access areas and processed food crops or non-food crops.