Effects of solids accumulation in three full-scale horizontal flow treatment wetlands

Subsurface system (SSF) treatment wetland (TW) is a global applied technology with low operating and maintenance costs, good landscape, and weather resistance (Zhong et al., 2022). As well known, the long-term operation of SSF-TW results in the accumulation of bodies from physical, chemical, and biological processes, causing substrate clogging (Zhou et al., 2020). Although clogging is one of the crucial issues that attracted increasing attention in the scientific community, there are still several gaps in its understanding, especially in its genesis and assessment. Void pores clogging in horizontal subsurface flow (HF) TW may severely impact water permeability, making the substrate prone to be clogged by solids accumulation, biofilm growth, and root filling causing hydraulic malfunction and expansive management costs. This study aims to evaluate the behaviour of three full-scale HF-TW with different operation life times, located in Eastern Sicily (Italy), regarding accumulated solids nature and build-up process in relationship to the hydraulic conductivity variation of the substrate