BACKGROUND: Ultrafiltration (UF) coupled with ozonation (O-3) may be a promising process for removing endocrine disrupting chemicals (EDCs) from secondary effluent. One key point in employing this process is whether the UF unit should be set in front of or after the O-3 unit. So, in this paper, two systems with reversing series of UF and O-3 units were developed and operated to assess which one is better. RESULTS: Results showed that the O-3-UF process exhibited 13% higher UV adsorption removal efficiency than the UF-O-3 process. EDCs concentration and estrogenicity removal efficiency of the O-3-UF process was 2-7% and 10%, respectively, greater than that of the UF-O-3 process. In addition, the O-3-UF process achieved higher membrane filtration flux (28.9 LMH) than that (25.6 LMH) of the UF-O-3 process. A pilot scale O-3-UF reactor was designed to treat a real secondary effluent and achieved effective EDCs removal (average 75.2%) and estrogenicity removal (average 84.3%). CONCLUSIONS: This study indicated that the O-3-UF process can effectively remove EDCs from secondary effluent and produced weaker membrane fouling than the UF-O-3 process; therefore, it was suggested for treating EDCs-containing secondary effluent. (C) 2016 Society of Chemical Industry