In partnership with SBS-Engenharia, Lda., Excellens developed the Inha ETAR project, using Biomatrix ® technology developed and owned by SBS-Engenharia, Lda. This technology is a modification and improvement of traditional SBR technology. The Biomatrix treatment system ® is specially adapted for systems that require the removal of nutrients (nitrogen and phosphorus). The mathematical design and modelling of tanks, reactor, thickener and other organs was made in a systematic integration with the hydraulics project, to ensure the development and adjustment of projects simultaneously, subtracting the already known problems of reformulations and changes. The requirement at the level of watertightness and the control of retraction phenomena was imperative in terms of structural design. The construction phase was developed together with the builder in order to balance the premises of calculation and structural behavior, with the calendar of the work and monetization of the execution operations.