Seasonal and ageing effects on SFTW hydrodynamics study by full-scale tracer experiments and dynamic time warping algorithms Maximilien Nuel a,b , Julien Laurent a , Paul Bois a , Dimitri Heintz b , Robert Mosé a , Adrien Wanko a,⇑ a Icube, UMR 7357, ENGEES, CNRS, Université de Strasbourg, 2 Rue Boussingault, 67000 Strasbourg, France b Plateforme métabolomique, Institut de Biologie Moléculaire des Plantes, UPR 2357, CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France highlights  Seasonal characterization of SFTW hydraulic behavior in full-scale system.  Evidence of ageing effect on surface flow treatment wetland.  Breakthrough curves comparison by dynamic time warping method.  Highest short-cutting index and strongest advective flow regime occurred in winter. graphical abstract article info Article history: Received 13 January 2017 Received in revised form 4 March 2017 Accepted 6 March 2017 Available online 16 March 2017 Keywords: Surface flow constructed wetland Residence time distribution Dynamic time warping Fluorescent tracers Hydraulic behavior abstract Surface flow treatment wetlands (SFTW) are considered as ecological engineering treatment wetlands used for wastewater and stormwater treatment. In France SFTW are commonly located between the wastewater treatment plant (WWTP) and the receiving aquatic environment. Furthermore, they are not considered as a regulatory treatment step but as a complementary element to WWTP. In this regard, there is currently no established design and sizing rule since (i) they are built on the remaining space after WWTP construction, (ii) it is a nature-based system, subject to high variability and complex inter- actions and (iii) feedback on ageing effects is lacking. This study permitted to qualify and to quantify sea- sonal and ageing effects on the SFTW hydraulic behavior which is a pond. The combination of fluorescent dye tracer application in a real system and data analysis by dynamic time warping (DTW) allowed to per- form efficiency comparisons between all campaigns. Similar behaviors of dimensionless retention time distributions were observed for all campaigns. They were eventually linked with the SFTW shape. The analysis of these curves highlighted that the measured mean residence time was always lower than the nominal hydraulic residence time, due to preferential flow and dead-zones. A statistical approach suggested that the winter hydraulic behavior was characterized by the highest short-cutting index and strongest convective flow regime in comparison to others campaigns. A lower vegetation density, espe- cially subaquatic plants, and presence of important preferential flow could explain this observation. DTW processing on RTD curves shed light on the ageing effect that has a much bigger impact than seasonal effect. This is mainly due to sediments accumulation, sludge and vegetation development. Ó 2017 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2017.03.013 1385-8947/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail addresses: mnuel@engees.eu (M. Nuel), julien.laurent@engees.unistra.fr (J. Laurent), p.bois@unistra.fr (P. Bois), dimitri.heintz@ibmp-cnrs.unistra.fr (D. Heintz), mose@unistra.fr (R. Mosé), wanko@unistra.fr (A. Wanko). Chemical Engineering Journal 321 (2017) 86–96 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej