Developing filters for laundry machines to prevent microfiber release

Abstract

Microplastics (MPs) represent one of the most pervasive environmental pollutants in the modern era, with profound implications for ecosystems and human health. Among these, microplastic fibers originating from synthetic textiles during laundering are a particularly significant source of pollution. These fibers are released during washing cycles, bypass standard wastewater treatment processes due to their small size, and accumulate in aquatic, terrestrial, and even atmospheric environments. The resulting contamination poses risks not only to marine life but also to human health, as these fibers enter food chains, water supplies, and the air creatures breathe. If current trends persist, it is projected that over 22 million tons of synthetic fibers will be discharged into the environment by 2050, making this a critical environmental and public health issue. This thesis tackles the urgent problem of microplastic fiber pollution by focusing on the design, development, and optimization of textile-based filtration systems for household washing machines. The primary objective is to prevent the release of microplastic fibers into wastewater at their source. Unlike broad strategies that target post-discharge remediation or changes in textile production, this study emphasizes source reduction through effective filtration mechanisms integrated into washing machines. By leveraging advancements in textile engineering, the research identifies optimal materials, structural configurations, and designs that maximize microplastic fiber capture without compromising the functionality of washing machines. The thesis commences with a comprehensive review of the literature, which underscores the environmental significance of microplastics, particularly those derived from textiles. Microplastic fibers, which account for 34.8% of global microplastic pollution, are released during the washing of synthetic garments, such as polyester and polyamide, which constitute a significant portion of global textile production. A single wash cycle can shed hundreds of thousands to millions of fibers, which subsequently evade conventional wastewater treatment and infiltrate natural environments. These fibers are not only ingested by marine and terrestrial organisms but have also been detected in human food sources, drinking water, and the air, posing significant health risks such as oxidative stress, hormonal disruption, and even cancer. The environmental review also highlights the limitations of existing filtration systems. While some commercially available products, such as Guppyfriend bags and Cora Balls, capture a fraction of the fibers during laundering, they are insufficient to address the magnitude of the problem. Similarly, current wastewater treatment plants are only partially effective in removing microplastic fibers, especially the smallest particles. Consequently, integrating filtration systems directly into washing machines emerges as a practical and impactful solution. The experimental section of this thesis focuses on developing and testing woven textile-based filters designed specifically for household washing machines. Key variables examined include yarn structure, number of filaments, weave pattern, and weft density. These parameters were selected for their significant impact on filtration efficiency, durability, and compatibility with washing machine operations. Twelve fabric samples were produced using three different types of polyester yarns (monofilament, 36-filament multifilament, and 96-filament multifilament) and assessed for physical and functional properties, including basis weight, thickness, tensile strength, tear strength, stiffness, air permeability, and vacuum filtration efficiency. The samples were manufactured with plain and 2/2 twill weaves at two different weft densities (33 and 17 picks/cm). Additionally, surface morphologies were examined using scanning electron microscope (SEM). The results showed that increasing weft density led to higher basis weight and thickness across all samples. While twill weave fabrics generally exhibited slightly higher basis weight than plain weaves, the differences were not statistically significant. Twill weave fabrics consistently demonstrated greater thickness than plain weaves, attributed to the float structure in twill weaves that creates a looser and bulkier fabric. For tensile strength, plain weaves outperformed twill weaves due to their higher interlacing points, and an increase in yarn count further enhanced tensile strength. Regarding tear strength, loosely constructed fabrics with fewer interlacing points exhibited higher resistance in twill weaves as yarns moved and bunched together under force. Twill weave structures also had higher air permeability due to their more open structure. This research also explored broader considerations in filter design, including the influence of yarn type (monofilament vs. multifilament). Monofilament yarns, characterized by their smooth surfaces, exhibited advantages in terms of durability but were less effective at capturing smaller particles. In contrast, multifilament yarns, with their higher surface areas, demonstrated greater filtration efficiency but were prone to clogging and reduced throughput. The study concluded that an optimal filter design would likely involve a hybrid approach that combines the strengths of both yarn types. Stiffness tests confirmed that monofilament yarns exhibited greater rigidity than multifilament yarns, while air permeability tests showed higher values for twill weave and monofilament fabrics. These findings underscore the critical influence of fabric structure, yarn type, and weft density on both filtration efficiency and physical durability. Vacuum filtration tests revealed that plain weave fabrics had superior microplastic retention compared to twill weaves, owing to their compact structure and smaller pore sizes. The highest filtration efficiency, 96.60%, was achieved by the plain weave sample P36T-33-P, made with 36-filament yarns at a weft density of 33 picks/cm. This was followed by its twill counterpart P36T-33-T (92.87%) and the plain weave sample P36T-17-P (92.30%). Monofilament fabrics generally demonstrated filtration efficiencies below 90%. Results of the experiments revealed that woven filters with tighter structures and higher densities demonstrated superior microfiber retention capabilities. However, these configurations also may pose challenges such as increased pressure drop and reduced mechanical durability, necessitating a careful balance between filtration efficiency and operational practicality. The thesis further contextualizes its findings within the broader landscape of microplastic pollution mitigation. The research also emphasizes the need for regulatory action to mandate the inclusion of effective filtration systems in new washing machines, as proposed by the European Union's recent initiatives on plastic pollution. In addition to its scientific contributions, this thesis underscores the potential for academia-industry partnerships in addressing global environmental challenges. The research was conducted in collaboration with industry stakeholders, leveraging their resources and expertise to develop practical, scalable solutions. The findings are not only relevant to the academic community but also offer actionable insights for manufacturers, policymakers, and environmental organizations working to mitigate the impacts of microplastic pollution. In conclusion, this thesis marks an important progress in addressing microplastic pollution by presenting a scientifically supported and practical approach to a critical environmental challenge. By integrating textile engineering principles with real-world applications, the research offers a pathway for reducing microfiber emissions at their source, thereby contributing to the broader goal of preserving environmental and public health. The innovative filtration systems proposed in this study have the potential to transform household laundry practices and set a new standard for sustainable textile management.