Removal of Microplastics/Microfibers and Detergents from Laundry Wastewater by Microbubble Flotation

Microplastics (MPs), particularly microplastic fibers (MFs), released during laundry processes, constitute a major source of primary MPs in the water environment, raising growing ecological and environmental concerns. This study developed and evaluated a microbubble-enhanced flotation approach to effectively remove MPs/MFs and surfactants─essential components of commercial detergents and common pollutants─from laundry wastewater (LW). Through bench-scale and pilot-scale experiments, we investigated a wide range of parameters affecting recovery efficiency, focusing on MP properties (5 plastic types, 3 particle size ranges, and 4 concentration levels), water chemistry (5 detergent concentrations), and operational conditions (2 types of gases, 3 bubble size ranges, and 3 gas flow rates). Our results showed that under optimized conditions, microbubble flotation could effectively remove over 98 wt % of MPs/MFs and over 95 wt % of surfactants from LW. Moreover, the high removal rates achieved in bench-scale microbubble flotation processes were successfully reproduced in upscaling trials using a pilot-scale bubble column of 5.7 m in height. This work demonstrates the robustness and reliability of microbubble flotation for industrial LW treatment, providing a straightforward, cost-effective, and environmentally friendly solution for the concurrent removal of MPs and surfactants.