Application of Ultrafiltration, UV Radiation and Ozonation as Tertiary Treatment for Effluent of Isfahan North Wastewater Treatment Plant in Pilot Scale

The aim of this study is the pilot performance evaluation and comparison of wastewater disinfection methods consisted of ultrafiltration, ultraviolet radiation and ozonation, to tertiary treatment and effluent quality improvement in Isfahan north wastewater treatment plant. Therefore, the filtered effluent by a pretreatment unit from microscreen type entered the disinfection pilots. In this study, the membrane flux of ultrafilter (17.5-70 L/hr.m2), UV dose (400-3700 mW.s/cm2), ozone dose (10-40 mg/L) and contact time (1-15 min) with ozone were variable and TSS, Turbidity, COD, fecal and total coliform, before and after units were measured. The results showed that the total suspended solids were below the detection limits in UF effluent and it reduced at the maximum dose of UV radiation and at the highest concentration and contact time with ozone by 61.27% and 89.36%, respectively. Though the turbidity and chemical oxygen demand were not reduced by UV, their removal percentage in UF was 76 and 39%, respectively, and their maximum removal by ozone was 80.52% and 40.74%, respectively. Also, the fecal and total coliform was reduced in UF 5.28 and 5.08 log, respectively, and at the maximum UV radiation was 3.82 and 3.79 log; at the highest concentration and contact time with ozone it was 4.11 and 3.55 log, respectively. The results showed that influent quality and the loading in UF do not have a significant effect on their effluent quality. Also, the contact time to UV radiation compared to the average intensity of MP lamp radiation has a greater effect on the removal of coliforms. In ozonation, the influent COD had a major role in reduction of turbidity and COD. According to the results, the combination of microscreen and UF is an effective process for reducing the physical parameters and coliforms in the secondary effluent. It can provide the US Environmental Protection Agency standards for many uses (TSS≤5 mg/L, Turbidity≤2 NTU, Fecal coliform≤14 MPN/100mL). However, only a 300W MP UV lamp with a contact time of 40 s and (3700 mW.s/cm2) an ozone dose of 40 mg/L at a contact time of 15 min can meet the fecal coliform to the EPA standards for some uses including restricted urban uses, agricultural irrigation for processed or non-food crops (Fecal coliform≤200 MPN/100mL).