Inactivation of Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli present in treated urban wastewater by coagulation–flocculation and photo-Fenton processes

Abstract

The purpose of the current study is to evaluate the inactivation of three different kinds of bacteria usually present in municipal wastewater treatment effluents (Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli) using a coagulation–flocculation–decantation (CFD) process combined with photo-Fenton treatment at pH 5. Different concentrations of Fe³⁺–H₂O₂ (0.4/25, 5/25 and 15/25 mg L⁻¹), and H₂O₂ (25 mg L⁻¹) were evaluated for 210 minutes under artificial solar irradiation in a solar chamber ATLAS SUNTEST CPS+. The results were compared applying the CFD process before or after the disinfection treatment. The results of the bacteria inactivation show that the highest rate was observed using CFD–photo-Fenton treatment with 15 mg L⁻¹ of Fe³⁺ and 25 mg L⁻¹ of H₂O₂, obtaining the total inactivation of Pseudomonas sp., a 5.64-log inactivation of Enterococcus sp. and a 4.61-log inactivation of E. coli. In addition, turbidity and suspended solids decreased more than 90% with the combined treatments. The treated wastewater samples could be reused in urban, agricultural, industrial, recreational and environmental uses according to current Spanish legislation (RD 1620/2007).