CSO-CW for WWTP of Carimate (CO - 70.000 PE) - Global Wetland Technology

CSO-CW for WWTP of Carimate (CO - 70.000 PE)

The centralised WWTP of Carimate treats the wastewater from the combined sewer serving 11 towns in Como province (70,040 inhabitants). The Water Utiliy (Sud Seveso Servizi spa) wants to further reduce the pollutant load discharged in the Seveso River by treating also the combined sewer overflow (CSO) upstream the WWTP. To this aim, a constructed wetland for treatment of combined sewer overflow (CSO-CW) was designed by IRIDRA. The CSO-CW is a two-stage system. The first stage comprises two VF CW beds, each one further divided into 2 separated hydraulic sectors for a total area of 8500 m2. The second stage is a free water surface (FWS) CW of 4500 m2. The system is fed by a pumping system and automatically regulated by a PLC to properly treat the first more polluted fraction of the CSO events. The CSO-CW is able to intercept up to 500.000 m3/year (about 58% of the total estimated average CSO volume per year) and a COD load of 60 tCOD/year (about 60% of the total estimated CSO COD load per year). In other words, the CSO-CW is planned to intercept a pollutant load of 7700 p.e. (expressed in terms of COD), which were previously discharged untreated in the Seveso River. The maximum exploitation of CW ecosystem services is planned thanks to the FWS stage, which also aims to increase biodiversity and to recreate an area suitable for environmental educational activities. The riparian area along the left side of the Seveso river is planned to be involved in river restoration activities, with plantation of vegetation more suitable for riparian environments.