Biodirected Identification of Untargeted Toxicants in Industrial Wastewater Guides the Upgrading of Water Treatments

Because
industrial wastewater contains numerous chemicals and transformation
products (TPs), it is important to select efficient wastewater treatments
to remove toxic pollutants and their related toxicity. An integrated
framework for biodirected identification of untargeted toxicants in
industrial wastewater and evaluation of water treatments considering
the removal of causative toxicants and overall toxicity was developed.
A suite of in vivo bioassays, untargeted screening, and TP prediction
were combined and applied to typical industrial wastewater. The wastewater
was highly toxic with a toxic unit (TU) of 18.62, and organic substances
were characterized as the main toxicants. Twelve untargeted structures
and 13 of 338 TPs were tentatively identified in highly toxic fractions.
Four contaminants (tricyclazole, tebuconazole, propiconazole, and
hexaconazole) and one TP (2-methyl-4-benzothiazole) were confirmed
as causative toxicants, with tricyclazole contributing the most (≤21%)
to the detected TU. Further evaluation showed that although all of
the chosen advanced treatments could reduce the chemical oxygen demand
efficiently, bioaugmentation with sp. NJUST37 was finally promoted,
which removed 77% of TUs and 86% of tricyclazole, while activated
carbon and electrochemical filters showed limited removal of the dominating
toxicant and its related toxicity. Bioassay-directed analysis may
greatly improve the identification of untargeted toxicants in wastewater
and the upgrading of water treatments.