Characterizing the Organohalogen Iceberg: Extractable, Multihalogen Mass Balance Determination in Municipal Wastewater Treatment Plant Sludge

The large number and diversity of organohalogen compounds(OHCs)occurring in the environment poses a grand challenge to analyticalchemists. Since no single targeted method can identify and quantifyall OHCs, the size of the OHC iceberg may be underestimated.We sought to address this problem in municipal wastewater treatmentplant (WWTP) sludge by quantifying the unidentified fraction of theOHC iceberg using targeted analyses of major OHCs together with measurementsof total and extractable (organo)halogen (TX and EOX, respectively;where X = F, Cl, or Br). In addition to extensive method validationvia spike/recovery and combustion efficiency experiments, TX and/orEOX were determined in reference materials (BCR-461 and NIST SRMs2585 and 2781) for the first time. Application of the method to WWTPsludge revealed that chlorinated paraffins (CPs) accounted for most(similar to 92%) of the EOCl, while brominated flame retardants and per-and polyfluoroalkyl substances (PFAS) accounted for only 54% of theEOBr and 2% of the EOF, respectively. Moreover, unidentified EOF innonpolar CP extracts points to the existence of organofluorine(s)with physical-chemical properties unlike those of target PFAS.This study represents the first multihalogen mass balance in WWTPsludge and offers a novel approach to prioritization of sample extractsfor follow-up investigation. A multihalogenmass balance experiment in WWTP sludge revealedhigh levels of unidentified organofluorine and organobromine. Organochlorinewas characterized mainly by chlorinated paraffins.

Automated summary

The presence of a large number and diversity of organohalogen compounds (OHCs) in the environment presents a major challenge for analytical chemists. This study aimed to address this problem in municipal wastewater treatment plant (WWTP) sludge by quantifying the unidentified fraction of OHCs using targeted analyses and measurement of total and extractable (organo)halogen. The results revealed high levels of unidentified organofluorine and organobromine, and chlorinated paraffins were the dominant OHCs.