Water quality improvement in a full-scale tertiary constructed wetland: effects on conventional and specific organic contaminants.

The surface flow constructed wetland (SF CW) in Can Cabanyes (Granollers, Catalonia, northeastern Spain) was created as a part of a series of activities aimed at restoring a highly impacted fluvial peri-urban zone. The system is fed with a small part of the secondary effluent, which is not completely nitrified, from an urban wastewater treatment plant. Effluents in the SF CW were sampled between 2003 and 2006 for physical and chemical parameters and faecal bacteria indicators. In addition, 8 pharmaceuticals and personal care products (PPCPs) were measured in June 2005 and February 2006. The system showed a good reliability for ammonium and faecal bacteria removal, with average ammonium efficiencies between 64 and 87% and a removal of approximately 2 logarithmic units of Faecal Coliforms. A clear seasonal trend was observed for ammonium. The results for PPCPs demonstrated that the wetland has a good capacity for removing a large variety of these compounds; the removal efficiencies were higher than 70% for most of them, with the exception of clofibric acid (34%) and carbamazepine (39%). Although the chemical oxygen demand and total suspended solid removal rates were either low or zero because of the permanent eutrophic conditions of the system and the low incoming concentrations, the effluent quality is generally considered to be quite good.