Evaluating microfiber emissions and point-of-use filtration efficiency in household washing and drying cycles

This study investigates microfiber (MF) generation and discharge during household washing and drying cycles, focusing on the effectiveness of three commercial filtration systems designed to reduce MF discharge from wash wastewater. Experiments followed a standardized protocol and involved 10 washing cycles at 40 °C with polyester fleece garments, followed by drying cycles in a heat pump-based dryer. Key process parameters, such as drain flow rates and pressure gradients across the filters, were monitored in real-time. MF capture rates ranged from 35 % to 68 %, depending on the filter type. In some cases, a microfiber layer formed on the filter, enhancing capture but increasing hydraulic resistance, highlighting a trade-off between filtration efficiency and flow performance. Drying cycles also contributed to significant MF generation. However, the heat pump-based dryer safely captured most microfibers in the condensation water. While air vent-based dryers were not directly tested, they can reasonably be expected to pose a higher environmental risk due to their limited ability to contain airborne fibers. Drying did not reduce MF shedding during subsequent washes, emphasizing the cumulative nature of MF generation. This research underscores the strengths and limitations of current filter designs, highlighting the need for improved MF capture technology and standardized testing methodologies to reduce microfiber pollution.