Separation of microfibers from laundry waste water by hydrocyclone : In cooperation with Electrolux Professional

Abstract: Microfibers, textile fibres shorter than 5 mm, and are shed from fabrics during wear and released into the laundry effluent during washing. When passed through the wastewater treatment plant (WWTP), they adsorb toxins, heavy metals and pathogens before being released into the environment. Synthetic microfibers persist for long periods of time in aquatic environments and very little is known about the degradation of processed natural fibres. Hydrocyclonic separation was studied as a way to separate the microfibers from the effluent before being they get additionally contaminated at the WWTP. A hydrocyclone has no moving parts and functions by utilizing centrifugal force and the difference in specific gravity between the fluid and the particles that are to be separated. The separation efficiency is dependent on its dimensional and operation parameters. No previous studies on hydrocyclonic separation of microfibres were found. Polyester fleece blankets were washed. The effluent was filtered, and the filters weighed to determine the mass of the separated fibres. Sampling of the inhomogeneous effluent presented a challenge and larger sample volumes would be needed to adequately represent the population. Using a Büchner funnel, filter fouling led to filtration times of up to 6 h for 1 l of effluent. Dividing the 1 l samples into two 0.5 l samples, filtering separately and adding the weight reduced filtration time to 2 h and the results were not significantly different from filtering the whole 1 l sample with one filter. The hydrocyclones tested separated around 11% of the total weight of microfibers in the effluent, too low to be deemed viable. As only a few dimensional variables were tested, it could possible that a higher fraction could be separated with this method. Given that the commercially available filtration systems separate 30-80%, refining existing methods may yield better results.