Advanced on-site monitoring of industrial wastewater: integration of online biological and chemical tools to identify toxic compounds.

Monitoring of wastewater treatment plant (WWTP) effluents from complex industrial clusters with high temporal resolution is crucial for detecting and subsequently managing problematic compounds to reduce their release into the environment. This study explored the potential of combining biological early warning systems (BEWS) with a transportable high-performance liquid chromatography coupled with electrospray ionization and high-resolution tandem mass spectrometry (HPLC-ESI-HRMS/MS) platform (MS2Field) to detect and identify toxic pollutants in industrial-driven WWTP effluent. BEWS, using the organisms Daphnia magna, Chlorella vulgaris, and Gammarus pulex, provided real-time biological responses to micropollutants, while the MS2Field allowed continuous chemical detection of toxic compounds in parallel. Over a two-month monitoring period, significant correlations were observed between behavioural changes in the BEWS organisms and the presence of industrial target and non-target substances in the WWTP effluent. The parallel measurement and correlation of biological and chemical time series revealed four toxicity events and identified eight known and unknown compounds or compound classes associated with these toxicity peaks. Together with information from the industrial production site, this integrated approach enabled strategic source tracing of industrial emissions. When comparing data from the online monitoring tools with results from laboratory bioassays and chemical analysis of composite samples, it became obvious that high temporal resolution measurements are the key to accurately indicate toxicity trends. Otherwise, contaminant peaks were partially masked by dilution or degradation during storage. The approach offers traceability of sources for industries and regulators seeking to implement more effective and sustainable pollution management strategies.