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

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