Municipal effluent as a potential source of microplastics in the aquatic environment

In developed countries municipal wastewater effluents are the largest single effluent discharges, by volume. These effluents contain a complex mixture of both traditional and novel contaminants. One of the most recent contaminants of emerging concern is microplastics (MP), small fragments of plastic (<5 mm diameter) used in cleaning (industrial and personal) (primary MP) or formed by the breakdown of larger plastic items (secondary MP). Their potential effect on aquatic animals is largely unknown. Municipal effluents from waste water treatment plants are suspected to be a significant contributor of MPs to the aquatic environment and are thought to contain microbeads from various personal care products and fibres realised from synthetic fabrics during washing. The ability of waste water treatment plants (WWTP) to remove these microplastics and prevent their exposure in the aquatic environment is therefore very important and as yet un-investigated. In this study influent and effluent was collected from several stages (primary, secondary and tertiary) during the treatment process from three large (each with PE >300,000) treatment plants along the river Clyde, Glasgow, Scotland, representing the combined waste of over a million people. Samples are filtered and potential microplastics collected and positively identified using Fourier transform infrared (FT-IR) spectroscopy. Preliminary results indicate that 100 ml of influent from a single treatment plant resulted in 22 MP particles, mostly fibres of cellophane, nylon and a poly acrylonitrile/acrylate co-polymer. The results of this study will provide information on the efficacy of WWTPs in the removal of microplastics from waste water effluents.