Marta Alvir

Microplastics (MP) are found in nature in various forms. The transport and settling process of MP particles in water streams is highly influenced by particle size and shape. In order to investigate the impact of particle shape, an experimental analysis of settling behavior of flat square particles and 3D cubic particles in flowing water was conducted. The analysis is based on tracking the settling trajectories of particles of various size and using this information for calculating the drag coefficient cd in relation to the Reynolds number Re in the range of 80 to 280 for cubes and 50 to 110 for flat particles. The results were correlated with two shape parameters, sphericity ϕ and a newly proposed shape descriptor dimensionality δ. The final output is a model for particle shape-based cd estimation, mainly serving as an illustration of the potential of the proposed methodology.

In recent years, microplastic pollution has been given increasing attention in marine environments due to the hazard it poses for aquatic organisms. Plastic pipes are now being widely used in shipbuilding, and due to easy processing, they are often installed directly on ships. This includes the cutting and preparation of pipes for welding, which produces plastic debris in the immediate vicinity of the marine environment. Such plastic debris can easily become airborne, and when it is ultimately deposited into the water, it can be a contributor to marine microplastic pollution. This could be reduced if, during the design stage and outfitting stage, engineers would take into consideration ecological aspect of their design, which is currently not the case. Therefore, in this paper, suggestions for green shipbuilding practices, focused on the piping design and production phases, are presented for the possible reduction in operations with plastic pipes, with the main aim of reducing microplastic pollution. Based on these recommendations, additional economic and feasibility investigations are needed to obtain optimal results, which would be beneficial both from a manufacturing and ecological perspective.