At present, there is a lack of understanding regarding the extent to which various sources contribute to the total incoming load of microplastics (MPs) into wastewater treatment plants (WWTPs). This study investigated the contribution of an industrial textile laundry facility (ITLF) to the overall influx of MPs and their removal in two WWTPs. MPs were analysed by means of microscopic quantitative analysis in the wash water from a large textile laundry facility, as well as in the influent of the receiving WWTP. Additionally, influent and effluent flows of two WWTPs were analysed. Results demonstrated that a single-point emitter of MPs, i.e. an ITLF, contributed substantially (13%) to the overall influx of MPs in a WWTP. MPs were effectively removed (≥ 99.8% removal, particle size > 50 µm) in two separate WWTPs. As indicated in this study, actions mitigating the emission of MPs from single-point emitters are worthwhile and could be more cost-effective than implementing additional treatment processes in the WWTPs.

Literature frequently reports that colloids in aqueous matrices sorb a large fraction of pharmaceuticals. Since coagulation/flocculation removes colloids, it is expected that coagulation/flocculation in principle should be useful in concentrating pharmaceuticals in wastewater treatment, which would facilitate the treatment of these refractory compounds. In our present work, we researched the potential of coagulation/flocculation for removing pharmaceuticals from raw sewage. Results from jar tests showed that pharmaceuticals are hardly removed from sewage with coagulation/flocculation. To investigate the discrepancy between reported colloidal sorption and the lack of removal when removing colloids, we tested a commonly applied experimental setup, which makes use of ultra-filtration (UF), for determining the colloidal sorption of pharmaceuticals. The UF method under research was compared with an assessment making use of flocculation. Both methods, UF and flocculation, showed similar removal of colloids. However, during UF, the retention of pharmaceuticals reached values up to 93 ± 4 %. In contrast, when removing the colloids with flocculation, no pharmaceutical removal was observed. These results confirm that it is very likely to introduce an analysis bias in using UF membranes in the determination of colloidal sorption of pharmaceuticals. In fact, results predict an over-estimation caused by a direct retention of pharmaceuticals without any binding to colloidal matter. Overall results of the current work show that pharmaceuticals hardly sorb to colloids and herewith the absence of removal of pharmaceuticals during coagulation/flocculation is explained.