A pilot scale experimentation of a membrane bioreactor has been progressing since 1999 at Fusina-Venice wastewater treatment plant. Results showed that the limits introduced by Law Decree 30 July 1999 (Decree "Ronchi-Costa") can be fulfilled (except for Arsenic) and treated water is suitable for reuse purposes. According to the results reported in this paper, sizing and involved costs for the membranes application at Fusina wastewater treatment plant are presented. This can be the proper engineering solution for the Integrated Project Fusina.