The removals of other PCB isomers were
higher than those. Especially, for Mono-CBs and Hexa-CBs, the removal efficiencies were higher than 90% and high efficiencies of over 80% were achieved for Penta-CBs and Hepta-CBs. In comparison, the removals of PCBs were 20%–
91% in 26 WPCPs in New York and average removal were 77.3% described by Durell and Lizotte [23]. Higher removal was found in the WWTPs in Norway with more than 90% removal [24]. This was because PCB concentrations were very low with pg/L grade in the WWTP tested and the concentrations in other WWTPs were with ng/L grade. The
lower the concentration of PCBs is, the more difficult their removal becomes