Fused Filament Fabrication of Recycled Nylon-TiO2 Honeycomb Filters for Grey Wastewater Filtration

Abstract

This research focuses on fabricating a nylon honeycomb-structured three-dimensional (3D) filter for grey wastewater treatment using fused filament fabrication (FFF) and evaluating its performance in water treatment. The honeycomb module offered a tortuous pathway for particulate deposition during dead-end and depth filtration. A titanium dioxide (TiO₂) nanoparticle coating was applied via spin coating to enhance clogging effects and contaminant retention. A custom test setup was developed to analyse clogging behavior and estimate the filter lifespan. In dead-end mode, the coated filter achieved up to 85% removal of biochemical oxygen demand (BOD) and 80% removal of chemical oxygen demand (COD) during the first cycle, while depth filtration achieved 80% BOD and 75% COD removal. By the fifth cycle, removal efficiencies decreased to 58% BOD and 50% COD in depth filtration, indicating sustained performance over repeated use. Scanning electron microscopy (SEM) visualized progressive particulate accumulation; Fourier-transform infrared spectroscopy (FTIR) confirmed TiO₂ presence; and energy-dispersive X-ray spectroscopy (EDX) showed increased surface carbon content after filtration. Ultraviolet-visible (UV-Vis) spectroscopy confirmed moderate absorbance reduction at peak wavelengths. However, turbidity and total suspended solids (TSS) remained above acceptable limits (e.g., turbidity > 235 NTU; TSS > 410 mg/L), revealing the need for finer pore sizes or multilayer filtration. Clogging Index (CI) reached 0.45 in dead-end and 0.40 in depth filtration by the fifth cycle. The results demonstrate that this 3D-printed nylon-TiO₂ module provides moderate contaminant removal with rapid clogging kinetics, offering promise for non-potable reuse and decentralized greywater treatment applications.