Presence and behavior of metals in public sewage: long-term modelling with EPA SWMM

This paper reports a monitoring and modeling of the occurrence of metals in a WWTP inflow, identifying the different sources of metals in domestic, commercial/industrial wastewater and surface runoff, using the software SWMM. The developed model explained very well the hydraulic data, with errors around 1% in relation to the calibration dataset and 4% to the validation one. When explaining the quality data, the model was unable to predict Cu and Zn. The reason may be found in the well-known fraudulent industrial discharges, that, on the basis of our study represent respectively 59% and 23% of Cu and Zn total load. Instead we have observed good correspondence between the load peaks of Al and Fe predicted and the measured ones. From the mass balance, it was possible to see that most of the load of aluminum (over 70%) and iron (over 50%) is actually due to wash-off and infiltration water.