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Influence of a Bubble Curtain Device on Microplastics Dynamics
* 1 , 2, 3 , 4 , 1
1  Universidade of Beira Interior. Centre of Materials and Building Technologies (C-MADE)
2  University of Beira Interior.
3  Universidade de São Paulo
4  Universidade da Beira Interior
Academic Editor: Simeone Chianese


The environmental pollution caused by plastic waste has become a key-issue in recent years, given the significant threat posed on terrestrial ecosystems. One of the most discussed topics concerning plastic waste is their impact on marine environments, particularly, the effects caused by microplastics (MP) and its bioaccumulation in aquatic species. Despite rivers being the primary pathway for MP transport from terrestrial sources to marine environments, research on the transport mechanisms in river systems is scarce. To design efficient retention and collection systems, it is essential to understand and quantify MP transport in rivers. This work explores the use of a bubble curtain device to retain MP particles. The objectives are centered on the analysis of flow hydrodynamics in the presence of a bubble plume and the study of the parameters that influence the efficiency of the device. In the interest of studying the influence of bubble injection in the microplastics dynamics, a numerical study is performed using Ansys® Fluent 2019 R3. To accurately and more closely represent the problem’s physics, three central concepts are used: multiphase, turbulence and discrete phase modelling. By using these three concepts, the free-surface is closely tracked using the Volume of Fluid (VOF) method, the mean flow field is solved with a Reynolds-averaged approach (RAS) and the unsteady particle tracking of the microplastics are properly estimated with Discrete Phase Model (DPM). The injection of particles is considered to not have any interaction with the continous phase, following a one-way coupling philosophy that is valid when the particle concentration is low. Preliminary results show that injecting air at the bottom of the water channel creates a clear upward current resultant from the inlet velocity and buoyancy effects. MP particles are driven to the surface by the ascending current, and by getting attached to the rising bubbles. Once at the surface, the microplastics can be more easily removed. Ongoing research is focused on the efficiency of the retention system and in its dependence on the air injection velocity, flow velocity, water depth, and other governing parameters. Future research will look into newer and improved injection systems with a focus on exploring these studies experimentally.

Keywords: Microplastics; Bubble curtain; Numerical work