Nano-occurrence and removal of PCBs within the Europe's largest petrochemical MBR system

The occurrence of 45 PCBs was studied in a wastewater treatment plant (WWTP), which treats industrial wastewater from the zone of Porto Marghera (Venice, Italy) in an MBR, and in the Naviglio del Brenta River, which serves as a source of process water supply for this industrial zone. The focus of the study was placed on the comparison of levels of contamination of the WWTP effluent and the river water by selected PCBs in order to understand the major source of PCB pollution for the Lagoon of Venice and contrast them with the current legislation. Out of 45, 31 PCBs were detected in the WWTP at total median PCB concentration of 5.5 ng/L with a predominant presence of six indicator – PCBs (PCB 28, 52, 101, 138, 153 and 180), which accounted for 50–55% of total PCBs in both wastewater and sludge samples. The total PCB concentration was reduced by around 90% during the applied wastewater treatment to a median concentration of 0.5 ng/L at the WWTP effluent. In the samples collected from the river, 27 PCBs were detected at total median concentration of 2.1 ng/L, which is few times higher than the total PCB concentration found in the WWTP effluent. This result suggests that the current legislative limitations applied to the WWTPs effluent discharges into the Lagoon of Venice, regarding the presence of PCBs (i.e. absent) is rather arbitrary given the higher concentration levels encountered in river water than in the WWTP effluent of the studied industrial WWTP