Integrating Biological Early Warning Systems with High-Resolution Online Chemical Monitoring in Wastewater Treatment Plants

Detection of micropollutants
(MPs) in wastewater effluents using
traditional toxicity tests or chemical analysis with discrete samples
is challenging due to concentration dynamics. This study evaluates
a continuous monitoring approach for detecting MPs in wastewater effluents
using a combination of biological early warning systems (BEWS). Three
BEWS with Chlorella vulgaris, Daphnia magna, and Gammarus pulex were operated in parallel in a full-scale municipal wastewater treatment
plant. Concentrations of MPs were monitored by simultaneous online
chemical analysis using high performance liquid chromatography-high
resolution mass spectrometry (MS2Field). Over 5 weeks, behavioral
changes observed in the BEWS occasionally exceeded acute toxicity
thresholds, triggering alarms. These changes were related to MPs identified
by the MS2Field, to abiotic factors, or to operational parameters
of the BEWS. For one toxic event, behavioral responses were linked
to a pesticide, not authorized in Switzerland, at concentrations close
to literature EC50 values. Verification tests confirmed
that the pesticide in the effluent was the most likely cause for the
organism response. The study demonstrates the potential of BEWS as
a stand-alone technique for detecting contamination peaks in wastewater,
and identifies key limitations and critical factors that need to be
addressed to optimize the use of BEWS in wastewater monitoring.