In 1998, IRIDRA managed a project of constructed wetland at the tourism resort of Pentolina, in the Municipality of Chiusdino, Province of Siena. This plant is a tertiary treatment system for the effluent of a total oxydation plant (with forced oxygen) designed for 500 P.E. The constructed wetland system is composed of one horizontal subsurface flow basin of 550 m 2 . The system is characterized by a strong fluctuation of the number of users, that periodically changes from a few units during winter (10-15 P.E.) to 500 P.E. during summer.Monitoring of the plant is conducted by IRIDRA group in collaboration with ARPAT Department of Prato. The "ugly" total oxidation activated sludge plant has been dismissed in 2012! A 2stage VF(French)+HF CW is now taking care of the whole wastewater load treatment.