title: Mechanical resistance properties of gravel used in subsurface flow constructed wetlands: implications for clogging.
abstract: Gravel constitutes the filter medium in subsurface flow constructed wetlands (SSF CWs) and its porosity and hydraulic conductivity decrease over time (clogging), limiting the lifespan of the systems. Using gravel of poor quality accelerates clogging in wetlands. In this study, gravel samples from six different wetland systems were compared with regards to their mineral composition and mechanical resistance properties. Results showed that both mineralogy and texture are related to mechanical resistance. Accordingly, gravel with high content of quartz (> 80%) showed a lower percentage of broken particles (0.18-1.03%) than those with lower content of quartz (2.42-4.56% media broken). Although granite is formed by high durability minerals, its non-uniform texture results in a lower resistance to abrasion (ca. 10% less resistance than calcareous gravel). Therefore, it is recommended to use gravels composed mainly of quartz or, when it is not available, limestone gravels (rounded and uniform) are recommended instead. The resistance to abrasion (LAA test) seems to be a good indicator to determine the mechanical properties of gravels used in CWs. It is recommended to use gravels with LAA below 30% in order to avoid a rapid clogging due to gravel crumbling and subsequent mineral solids accumulation.
authors: Environmental Engineering Division, Department of Hydraulic, Maritime and Environmental Engineering, Technical University of Catalonia, c/Jordi Girona 1-3, Building D1, 08034 Barcelona, Spain.
authors: Anna
authors: A
authors: Pedescoll
authors: Fabiana
authors: F
authors: Passos
authors: Elisenda
authors: E
authors: Alba
authors: Joan
authors: J
authors: García
authors: Jaume
authors: J
authors: Puigagut
mesh_terms: D005374:Filtration / Q000379:methods*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry; D014872:Water Movements; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D014867:Water