Determination of Polychlorinated Naphthalenes in Landfill Leachates and its Removal in Wastewater Treatment Processes

Di-through octachlorinated naphthalenes (DiCNs, TrCNs, TeCNs, PeCNs, HxCNs, HpCNs and OcCN) in landfill leachates can be analyzed with the same cleanup procedure as dioxins. In this study, a modified method was developed by confirming the elution order of each isomer of polychlorinated naphthalenes (PCNs) in a chromatogram of a gas chromatograph/high resolution mass spectrometer (GC/HRMS) using an Rh-12 ms capillary column, which is mainly employed for the analysis of dioxins. Using this method, PCNs in landfill leachate samples and treated leachate samples from each corresponding wastewater treatment process were quantified. PCN concentrations in landfill leachates ranged from 8.0–12,000 pg/L, and DiCNs-PeCNs were detected in almost all samples. Removal of PCNs by flocculation and active carbon treatment was greater than that achieved by activated sludge treatment in wastewater treatment plants. Furthermore, by changing the temperature of the H2SO4 coated silica gel column in the modified method, it became possible to measure monochlorinated naphthalenes (MoCNs), which could not be measured previously. MoCN concentrations detected were much higher compared to concentrations of DiCNs-OcCN in most of landfill leachates. Unlike PCNs, MoCNs are not POPs, but they are nevertheless important for understanding the properties of landfill leachates.