Fate of microplastics in the drinking water production

Microplastics are ubiquitous and consequently enter drinking water treatment plants. Knowledge of the microplastic fate in drinking water production is still very limited, although explorative studies have shown tap water contains low contents of microplastics. In this study, we measure microplastic concentrations in drinking water sources and assess the effectiveness of various drinking water treatment facilities to reduce the microplastic concentrations in water to gain insight into the fate of microplastics. Two analytical techniques, laser direct infrared spectroscopy (LDIR) and optical microscopy, have been applied to cover the particle size range from 20 µm to 5 mm. In total five different drinking water sites were investigated using four different types of raw water (groundwater, surface water, dune filtrate and riverbank filtrate) for drinking water production. This research shows that drinking water treatment removes the majority of microplastics and that concentration of microplastics larger than 20 µm in tap water is less than 2 microplastics particles per litre. Between the different raw water sources it is found that groundwater had by far the lowest microplastics concentrations (< 1.000 microplastics per m³) and the highest concentration was found in riverine water, up to 460.000 particles per m³, specifically in the Lek Canal () (a canal connected to the river Rhine). On average the most abundant plastics found are polyamide (PA, 33%), polyethylene terephthalate (PET, 15%), rubbers (10%), polyethylene (PE, 10%) and chlorinated polyethylene (CPE, 7%). This study also showed that natural treatment steps, such as dune infiltration and sedimentation, remove microplastics effectively. However, this may introduce an adverse effect where microplastics potentially accumulate in the sediment and environment.