Disinfection by-products are of great concern in swimming pool water where water treatment generally involves a disinfection step with chlorine. In fact, swimmers can contribute a large quantity of organic matter that can lead to the formation of chloramines, chloroform and chloroacetic acids. These compounds can lead to health problems among the staff and pool users, especially babies or little children. The water quality improvement and productivity performance of the hybrid process, ultratiltration-adsorption, is investigated. An original work, this paper presents results obtained in a real pool system for the first time. An industrial unit was installed in a municipal swimming pool in Marseille (France) and the process was studied for more than 18 months. After a study on water quality according to pool usage (activity and number of swimmers), the influence of transmembrane pressure and filtration time on ultrafiltration performance was evaluated. Optimal ultrafiltration operating conditions were found to be at a transmembrane pressure (TMP) of 0.45 bar and a filtration time (T-f) of 60 min for the entire range of each water quality parameter studied. The filtration unit enabled water clarification, and the adsorption step limited the concentration of combined chlorine in water to 0.35 ppm, well below the limit given by the French legislation (0.6 ppm). Due to a succession of filtration and backwashes, permeability never decreased below 160 L h(-1) m(-2) bar(-1). In spite of difficult conditions in terms of frequent pool usage and total chlorine concentration, the membranes have shown promising flexibility in this hybrid process. (C) 2008 Elsevier B.V. All rights reserved.