Factsheet 11: Microplastics in wastewater treatment - Development of sampling and analysis methods for detection of input quantities into surface waters
It is not easy to determine how much microplastic is contained in wastewater and sewage sludge. In addition to plastic, countless other particles and substances are present. To reliably determine the concentration of microplastic particles, complex procedures for sampling as well as for removal of foreign substances and analysis of the microplastic particles are required.
Representative sampling is crucial to obtain scientifically usable data on microplastic levels in the environment. This requires an approximate idea of the microplastic occurrence in the medium under investigation. For water bodies, this can be done, for example, by individual sampling using a flow-through centrifuge.
The use of plastics permeates all areas of human life. Accordingly, microplastics are also produced in a variety of ways and are transported away via wastewater systems. However, little is known about which microplastic types and size distributions are found in the various wastewater streams, how well sewage treatment plants retain these loads and what ends up in water bodies.
Consumers are often unaware that millions of tonnes of plastic are improperly released into the environment. This can happen not only through improper disposal, but also through microplastic release from tyres or textiles. In the environment, the plastic breaks down into smaller and smaller pieces through exposure to sun or water and is dispersed by water or wind.
Factsheet 7.2: Microplastics in the aquatic food web - Impact and transfer analysis based on the example of roundworms (nematodes)
"To assess the ecologic danger posed by microplastics, one must also consider indirect effects in the food web", say Sebastian Höss (Ecossa) and Marie-Theres Rauchschwalbe (Bielefeld University). The researchers from the joint project MikroPlaTaS looked at these effects using nematodes as an example.
Plastic is now ubiquitous not only in the sea but also in many inland waters. In certain areas, such as at barrages or in dams, the flow velocity decreases. As a result, the particles previously held in suspension by the current begin to sink to the bottom of the water and can then accumulate in the sediment.
Factsheet 5.1: Removing microplastics from industrial wastewater - Process improvements through the use of flocculants
Microplastics can enter our wastewater along the entire value chain. Removal options exist primarily in wastewater treatment plants, here in the form of filtration, flotation and sedimentation processes. The removal performance of wastewater treatment plants determines how much microplastic is discharged into the environment.