The term ‘microplastic’ is not consistently defined but is typically considered to refer to small, usually microscopic, solid particles made of a synthetic polymer. The European Chemicals Agency (ECHA) define microplastics as “very small (typically smaller than 5 mm) solid particles composed of mixtures of polymers (the primary components of plastics) and functional additives.” Anthropogenic generation of microplastics is a pertinent and global problem that is escalating steadily. Two of the major sources of microplastics in Sweden (IVL report) are particles generated by traffic and washing machine effluents. Early capture, and water-phase capture will lower the risk of particles becoming airborne and the risk of particle down-sizing. Particles generated from traffic are of high societal and environmental interest, and that such particles should preferable be captured before they are downsized enough to be air-borne. Traffic-generated particles end up in run-off waters and are not captured, while household-generated microplastics are removed in water-treatment plants. CSP6 Will look for potential synergies with studies within the programme Mistra Nanosafety and the possibility of joint activities.

The work will be divided into two potentially separate areas:

CSP6.1 Washing machine effluents. Using the lignocellulosic functionalized materials developed in phase II, we will develop filters for the outlet of domestic washing machines in a PoC case. The base materials need functionalization to boost the filter selectivity. Adsorption/selectivity allows for capturing small particles although the pore size is larger which is necessary to achieve efficient removal with less pressure drop. Filters will be prepared by structuring (e.g. 3D-printing, air-laid technology, papermaking-like process). The challenge will be to develop the materials which will hinder the microplastics, be selective to rejection of microplastics and no other particles and be amenable to being backwashed/regenerated for long-time performance, without a need for frequent exchange of the filter. This PoC also involves development/identification of analysis methods that allow for size and surface chemistry determination, over a large range of particle sizes. Mimbly is developing filtering techniques for water effluents (e.g. laundry process) and water recycling and will contribute with model water systems and processed laundry effluents, produced in their test labs and field tests including both industrial and home-use washing machines. The filters will be evaluated in the labs of MoRe and SU, with respect to morphology and mechanical properties (dry and wet state). SU will also perform filter performance tests with respect to water permeability (flux), capturing efficiency and long-term effects. Both the standard Mimbly filters, the enhanced filters developed within the project and the traditional microfiltration filters will be tested in parallel treating the same water during a prolonged time.

CSP6.2 Run-off water. This PoC study aims to develop a long-term and sustainable solution for rainwater/stormwater/run-off water management. In synergy with CSP6.1 and the development of functional lignocellulose in phase I, we will explore the use of these materials in filters that are inserted as a barrier in run-off water inlets. The first activity will be functionalization for filter selectivity. The filters should trap target microplastic particles while sand passes to ensure efficient capture combined with high throughput. Similar technologies and products as planned in the CSP 6.1 will be considered. We will develop filter solutions and test them in bench-scale using model water or real water from traffic or sports grounds, in the lab environment. The water samples and the filters after passing the water through will be evaluated. Flux, chemistry, and concentration in the inlet and outlet water, and state-of-health of the filter will be the most relevant parameters to consider. An important property of the filter solution is the easy removal and replacement, which also need to be considered in the design and iterated with the expertise on scaling in WP2. After the bench-scale evaluation, we aim to establish contacts with end users (gas stations, sports training facilities) to evaluate the performance of these solutions in relevant environment.

For both cases CSP6.1 and CSP6.2, protocols for size and chemistry analysis will be developed. Suitable references (e.g. Arizona road dust for airborne particles) will be identified. Filters will be analyzed for efficiency and flow capacity before and after exposure to particles. The technology and material solution are refined individually for CSP6.1 and CSP6.2 based on the specific requirements and boundary conditions for each case.

CSP6 Leader: Sven Norgren, MoRe
CSP6 Deputy Leader: Anna Svedberg, MoRe

Involved partners: SU; KTH; RISE; IVL; MoRe; Mimbly