<i>In Situ</i> Calibration of a Tube Passive Sampler in Wastewater Effluent with Adjustable Volumetric Flow for the Assessment of Micropollutants with Fluctuating Concentrations

We present a versatile flow-through tube passive sampling device (TPS), with a controllable feedwater volumetric flow, that can be calibrated <i>in situ</i> against the feedwater load of organic micropollutants (OMPs). This semipassive approach has the advantage of a determinable water load feeding the sampling device. The design of the TPS allows for new sampling scenarios in closed piping while providing stable and controlled sampling conditions. The calibration referencing an OMP's feedwater load can describe the uptake behavior from wastewater treatment plant effluent with potentially highly fluctuating OMP concentrations. The TPS and its load-dependent calibration under realistic environmental conditions proves possible for a variety of organic trace substances in a challenging matrix. Nine of the 20 monitored representative OMPs could be calibrated load-dependently, leading to a good agreement between the calculated concentration from the TPS and the average concentration of corresponding direct measurements. Due to the simple measuring principle and the membrane-less discs, many influencing factors such as diffusion, turbulence, and lag time phenomena can be neglected. The TPS could support the existing online measurement analytics in a (process-) water treatment plant by delivering integrated water concentrations for discharge monitoring.