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Evaluation of Combined Peracetic acid and UV treatment for Disinfection of Secondary Wastewater Effluent
Namboodiri, V. AND A. Garg. Evaluation of Combined Peracetic acid and UV treatment for Disinfection of Secondary Wastewater Effluent. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/172, 2017.
•This pilot scale study was designed for providing necessary parameter optimization for the field study that will be conducted along with the City of Cincinnati at their WWTP in September, 2017. This pilot-scale study examined various parameters such as the effectiveness of using PAA, UV, and PAA pretreatment for UV disinfection on the inactivation of enterococci, fecal coliforms, E. coli in secondary wastewater effluent. This study shows that pretreatment with PAA can potentially reduce UV energy usage. Other expected benefits include improvement in UV treatment efficiency (even with turbidity), reduce bulb replacement frequency and reduce bacterial regrowth. UV energy usage is about >130mJ/cm2 at WWTPs for secondary effluent treatment and can be reduced to <80mJ/cm2 with pretreatment using PAA thereby reducing overall treatment cost. A more detailed and evaluation will be performed during the field study.
The current study evaluates the effectiveness of the combined application of Peracetic acid and ultraviolet radiation as alternative disinfectant agents to the traditional chlorination of wastewater effluents. Various pathogens (E. coli, enterococci and fecal coliforms) were evaluated in the study. Four experiments were conducted using low to high PAA levels and UV dosages. E. coli and enterococci were resistant to low to moderate PAA dosage (0.5- 1 mg/L). These microbes can be removed effectively at high PAA dosage (2.5 mg/L) with 30 min contact time. Fecal coliforms were completely inactivated even at a low PAA dose of 0.7 mg/L. E. coli was more susceptible to UV disinfection than enterococci at low UV dosages. Enterococci required at least 40 mJ/cm2 for 2.5 log inactivation. In combined PAA + UV treatment, low UV intensities between 7 – 40 mJ/cm2 showed poor disinfection performance at a low PAA concentration of 1.5 mg/L. High UV intensities of 120 and 60 mJ/cm2 inactivated all the pathogens to below detection levels even at low to moderate PAA (0.7 mg/L and 1 mg/L) pretreatment concentration. Combined PAA + UV treatment at 1 mg/L (for 15 and 30 min contact time) + 120 and 60 mJ/cm2 did not show any regrowth of microbes, whereas PAA only disinfection with 15 min contact time showed regrowth of enterococci and fecal coliforms. UV only disinfection showed E. coli regrowth.