Info from the Spanish case study

Objectives: of the study is to gain

• insights into current contamination patterns
• possible sources
• loads and fluxes of microplastics in a selected freshwater system

The selected site is the Henares river basin, located in a Mediterranean continental semi-arid region in central Spain (see map).

• Three different river sites, for sampling water and sediment, characterized by:
  (1)  vegetated and forest areas
  (2)  agricultural areas
  (3)  urban/industrial

• Five wastewater treatment plants (WWTPs) with different characteristics (treatment steps, person equivalent, etc.) for sampling untreated and treated WW and sludge.
• Runoff water is collected in three experimental plots:
  (1)  recently treated with WWTP sludge
  (2)  historically treated with WWTP sludge
  (3)  never treated with WWTP sludge (control)

• Water samples (up to 10 m3 of river water, up to 200 L of waste water) are filtered through plankton nets of different mesh sizes (350, 200, 55, 20 mm) to collect even smaller microplastics, expected to not be retained during wastewater treatment.

First preliminary results indicate that WWTP effluents are not the most relevant source for microplastics in the Henares watershed. Microplastics also arise from additional sources, e.g. from the degradation of larger plastic particles directly in the stream environment or from surface runoff.