Do wastewater treatment plants act as a potential point source of microplastics? Preliminary study in the coastal Gulf of Finland, Baltic Sea

• Published in: Water science and technology 2015-11, Vol.72 (9), p.1495-1504
• Main Authors: Talvitie, Julia, Heinonen, Mari, Pääkkönen, Jari-Pekka, Vahtera, Emil, Mikola, Anna, Setälä, Outi, Vahala, Riku
• Format: Article
• Language: English
• Subjects: Archipelagoes; Biofiltration; Coasts; Effluents; Environmental impact; Environmental science; Eutrophication; Fibers; Filtration; Finland; Fourier transforms; Hazardous materials; Influents; Microplastics; Particle concentration; PCB; Plankton; Plastics; Plastics - analysis; Polychlorinated biphenyls; Receiving waters; Removal; Sedimentation; Sedimentation & deposition; Surface water; Waste Disposal, Fluid; Waste Management; Waste Water; Wastewater; Wastewater treatment; Wastewater treatment plants; Water; Water bodies; Water Pollutants, Chemical - analysis; Water Pollution
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2015.360

This study on the removal of microplastics during different wastewater treatment unit processes was carried out at Viikinmäki wastewater treatment plant (WWTP). The amount of microplastics in the influent was high, but it decreased significantly during the treatment process. The major part of the fibres were removed already in primary sedimentation whereas synthetic particles settled mostly in secondary sedimentation. Biological filtration further improved the removal. A proportion of the microplastic load also passed the treatment and was found in the effluent, entering the receiving water body. After the treatment process, an average of 4.9 (±1.4) fibres and 8.6 (±2.5) particles were found per litre of wastewater. The total textile fibre concentration in the samples collected from the surface waters in the Helsinki archipelago varied between 0.01 and 0.65 fibres per litre, while the synthetic particle concentration varied between 0.5 and 9.4 particles per litre. The average fibre concentration was 25 times higher and the particle concentration was three times higher in the effluent compared to the receiving body of water. This indicates that WWTPs may operate as a route for microplastics entering the sea.