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Settling model to predict microplastics removal efficiency in wastewater treatments
Summary
A mathematical settling model was built to predict how efficiently wastewater treatment plants remove microplastics based on particle density, size, shape, and surface loading rates. The model shows that dense, large, spherical particles settle most readily, while light fibers and films are far harder to remove — providing treatment plant operators and engineers with a practical tool for optimizing processes to reduce the discharge of microplastics into rivers and coastal waters.
Abstract Microplastics (MPs) are plastic particles less than 5 mm and become a good carrier and vectors for contaminants in the environment. Current wastewater treatment technologies, including preliminary treatment, primary treatment, secondary treatment, and tertiary treatment, have a certain removal efficiency for MPs or nano‐scale plastic particles. The settling treatment is employed in several wastewater treatment processes. This work built a settling model based on the Reynolds number, drag coefficient, and settling mechanism to predict the microplastics removal efficiency. Microplastics with larger density difference with wastewater, larger size, and CSF closer to 1 are easily captured and have a higher removal efficiency. The calculated removal efficiency according to density, size distribution, different shapes, and the surface loading rate in the operation of wastewater treatment is in a reasonable removal efficiency range. The removal efficiency increases when the surface loading rate decreases.
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