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The purpose of this paper is to study the transformation of some macropollutants including hydrocarbons, surfactants and metals in Milan west sewer basin. The study is part of a wider research (named SWARMNET and proposed by Politecnico di Milano and Metropolitana Milanese S.p.A and has been classified as fundable by the Ministry of Education, University and Research of Italy), aiming at installing a monitoring system for measurement of accidental discharge of pollutants from industrial activities and real-time protection of the wastewater treatment plant (WWTP) by avoiding dangerous discharges entering the sewers. Good effluent and waste sludge quality allow safe agricultural reuse of both streams. Other objectives include food safety, lower treatment costs and reduction of pollution of soil, surface and groundwater.

The west basin of Milan sewer network, discharging to San Rocco WWTP was considered. Among 700 industries, 16 have been selected for their specific characteristics and/or high industrial pollution load. A quality model was coupled with a hydraulic model to evaluate the effect of pollutants transport in the network.

Heavy metals, surfactants and hydrocarbons have different behavior from biodegradable domestic sewage and can be modeled as conservative matter conveyed by advection only. Results show that the concentration values of these macropollutants at the inlet of the WWTP are below the Italian standard values with the exception of Cadmium and Mercury. These heavy metals should be considered in the planned sampling campaign.

This study will estimate environmental benefits and both methodology and monitoring techniques can be extended to other cities in Italy and Europe.