Discover more at Additive Manufacturing Advantage: Energy, on September 17. Register for free!
Researchers from Khulna University of Engineering and Technology (KUET) have developed a 3D printed honeycomb filter made to treat greywater from domestic sources.
The filter was produced on an Ultimaker FFF 3D printer, using virgin nylon filament blended with recycled material obtained by depolymerising discarded nylon fabric, then coated with titanium dioxide (TiO₂) nanoparticles. Nylon was selected for its chemical resistance, strength, and durability under repeated exposure to wastewater, making it more suitable than other common 3D printing materials such as PLA, ABS, or PETG.
Led by Sumit Kanti Saha from the Department of Textile Engineering, the project also saw contributions from Jashore University of Science and Technology. Published in Micro & Nano Letters, the work explores a low-cost, reusable option for non-potable water applications. While the results are promising, the team notes that further refinement is needed before the design could meet drinking water standards.
Greywater trials and performance results
Measuring 195 × 195 mm with 5.44 mm hexagonal cells and 58% porosity, the honeycomb structure was designed to balance surface area, mechanical stability, and efficient fluid flow. Printing with recycled nylon posed challenges such as moisture absorption and slight filament diameter variations, which the team addressed by pre-drying the material and reducing print speed.
After printing, the filter was coated with TiO₂ nanoparticles via spin coating, creating a surface that encouraged contaminants to cling and form a dense cake layer early in the filtration process.
According to the team, tests were carried out on greywater collected from residential facilities using two filtration modes. In dead end filtration, water flowed perpendicularly through the filter surface. Whereas in depth filtration, it passed through a cube of stacked honeycomb layers, trapping contaminants throughout the structure.
Both configurations were tested for five consecutive cycles without cleaning. In the first cycle, the TiO₂-coated filter in dead end mode removed up to 85% of biochemical oxygen demand (BOD) and 80% of chemical oxygen demand (COD). Depth filtration removed 80% BOD and 75% COD during the first cycle. By the fifth cycle, these rates had fallen to 62% BOD and 55% COD for dead end, and 58% BOD and 50% COD for depth filtration.
Microscopy revealed heavier particle deposits on TiO₂-coated surfaces, while energy-dispersive X-ray spectroscopy confirmed the coating and detected higher carbon content after use, signalling captured organic matter.
Despite these results, turbidity and total suspended solids (TSS) remained well above Bangladesh’s drinking water limits. After treatment, turbidity ranged between 235 and 247 NTU, far exceeding the 10 NTU standard, and TSS stayed above 410 mg/L, compared with the allowable 10 mg/L.
The large pores and open structure let finer particles pass through. Clogging patterns also differed: in dead end mode, the flow rate dropped from 20 to 7 mL/min over five cycles, with pressure rising from 5 to 35 Pa; in depth filtration, flow declined from 25 to 10 mL/min and pressure increased from 3 to 30 Pa.
The clogging index reached 0.65 for dead end and 0.60 for depth filtration, prompting the authors to suggest maintenance options such as backwashing or chemical rinsing to extend the filter’s lifespan.
Using recycled nylon cut material costs by up to 40%, bringing the cost per module to under $2 USD. While 3D printing is slower than industrial manufacturing, it enables local production without moulds, making it well suited to small-batch and decentralised water treatment.
The researchers see this as a potential option for applications such as irrigation, toilet flushing and cleaning. They recommend reducing pore size, adding multiple layers or combining with finer filtration media to improve turbidity and TSS removal, and fine-tuning TiO₂ loading to balance strong initial performance with a longer working life.
3D printing boosts industrial water recovery
With growing demands for sustainability, industries worldwide are under increasing pressure to find efficient ways to recycle water.
High-performance ceramic 3D printers and materials manufacturer Lithoz and Evove collaborated to produce Separonics ceramic filter membranes for lithium extraction and industrial water recycling, using the CeraFab S320 lithography-based ceramic manufacturing system. The LCM process enabled tailored geometries, enhanced durability, lowered tooling costs, and supported efficient large-scale production.
Made from durable alumina ceramic, the membranes were built by stacking 20 precisely engineered segments, each 10 cm in diameter and 5 cm in height, into a 1 m filtration module with uniform pore size and distribution. This configuration delivered five times higher output, reduced energy use by 80%, and recovered 80% more water than conventional methods.
Elsewhere, NTU-spin off Nano Sun launched a 3D printing facility in Tuas to produce water filtration membranes. Created in a single printing step, the membranes were reported to be five times more efficient than conventional polymer or ceramic-based options.
The plant can produce up to 600 m² of membranes per day for sectors including semiconductor manufacturing and wastewater treatment. Developed under the guidance of NTU Associate Professor Darren Sun, the technology uses fine strands to capture pollutants while reducing space, labor, and resource needs. At the time of reporting, the $6 million facility had already secured contracts for uses such as wastewater treatment, kidney dialysis, and potential applications in synthetic skin production.
Help choose the 2025 3D Printing Industry Awards winners – sign up for the Expert Committee now!
To stay up to date with the latest 3D printing news, don’t forget to subscribe to the 3D Printing Industry newsletter or follow us on Twitter, or like our page on Facebook.
While you’re here, why not subscribe to our Youtube channel? Featuring discussion, debriefs, video shorts, and webinar replays.
Featured image shows the dead-end filtration technique. Image via KUET.
