Photolysis in natural aquatic environment might be an important elimination process for the light sensitive antibiotics, such as fluoroquinolones. Photolytic degradation of antibiotics present in wastewaters and natural aquifers can result in generation of new products that may be even more toxic than the parent compound. Therefore, it is important to identify these products and to remove them before entering, for example, drinking water sources, whereby the role of membrane processes is irreplaceable. In this study photodegradation of enrofloxacin (ENRO) in aquatic media was performed at two different pH values, 4 and 8. Four and three photodegradation products (PDPs) with different molecular weight were identified at pH 4 and 8, respectively. All of them, together with the enrofloxacin as the parent compound were removed almost completely (>99%) by reverse osmosis (RO) and tight nanofiltration (NF) membranes, while by loose NF membranes >92%, except for the smallest PDP with HL membrane (37%) at pH 8. The minimum amount of the compounds in the permeate is the proof that most of the selected RO/NF membranes make an effective barrier for them. The size exclusion was the main rejection mechanism, while the physico-chemical interactions and electrostatic repulsion/attraction probably had influence on the overall rejection by loose NF membranes for the smaller photodegradation products of ENRO. (C) 2013 Elsevier B.V. All rights reserved.