Résumé
Many studies exist about constructed wetlands (CWs) performance optimization, especially for organic compounds and nutrients removal, and describe optimal sizing, design and operation of CWs depending on the inlet wastewater (WW) to be treated. Co-benefits of CW make this type of system quite challenging with classical activated sludge process but performance still needs demonstration for adoption with reuse objectives. Specially the water quality provided may orientate the type of water reuse. CWs still face issues such as clogging and poor nutrient removal. Earthworms (EWs) are macro-invertebrates inhabiting soil ecosystems. Due to their high influence on soil physics, chemistry and biology, they are nicknamed “ecosystem engineers”. They are known for their positive influence on the ecological service of water purification in natural ecosystems (Liu et al., 2017) and their ability to thrive in CWs has been noticed (Li et al., 2011; Lavrnić et al., 2019; Gilibert et al., 2022). Vertical subsurface flow constructed wetlands (VSSF-CWs) have been identified as viable habitat for EWs (Li et al., 2011). A quite abundant literature exists on enhancing CWs or similar WW treatment technologies such as vermifilters (VF) or macrophyte-assisted vermifilters (MAVF) (Li et al., 2011). Nevertheless, among all this literature, most of the studies are carried out at lab scale, while studies carried out at larger scale and in open-air systems (mesocosms) are scarce. They also do not feature clear results and oftenly do not use replicates which do not allow to be conclusive on EW potential for CWs enhancement. This work studies the effect of EWs’ inoculation in mesocosm (0.2 m2) and pilot (5 m2) scale systems on the campus of Toulouse University. This experimental system allows replicates and parallel experiments with filters (10 mesocosms and 3 pilots) for testing research hypotheses with statistical analyses. A combined approach of hydraulic tests and water quality assessment is intended to evidence EWs effect on the process.