Reduction of microparticles and microorganisms in process fluids from a turning center using nanofiber filtration and ozone: An experimental multimethod approach

• Process fluids from a turning center were heavily contaminated with microparticles and microorganisms. • SEM/EDS revealed Fe-, Al-, and Si-containing oxide particles with sizes between 5–50 µm. • Nanofiber filters (esp. BERRY) achieved over 69% particle removal efficiency. • Ozonation effectively eliminated culturable bacteria (reduction to 0–8 CFU/mL). • qPCR revealed residual DNA, indicating VBNC bacterial forms post-ozonation. • Combining nanofiltration and ozonation provides a promising chemical-free strategy for process fluid regeneration. Process fluids (MWFs) play a crucial role in machining operations by providing lubrication, cooling, and chip removal. Their quality directly impacts production efficiency and the service life of equipment. This study aimed to comprehensively assess the contamination of MWFs by microparticles and microorganisms in a turning center and to experimentally evaluate the effectiveness of advanced nanofiber filtration and ozonation in their removal. Five types of nanofiber filtration materials were tested using high-resolution microscopic and microbiological methods, including confocal microscopy, SEM/EDS, culture-based analysis, and quantitative PCR. The dominant contaminants were identified as iron, aluminum, and oxidation product particles ranging from 5 to 50 µm in size. The most effective filtration material was the Berry (Fiberweb, Synergex pure) nanofiber filter, achieving a removal efficiency of 69.3%. Microbiological analysis revealed the presence of potentially pathogenic strains, including Pseudomonas aeruginosa, and demonstrated that a 30- minute ozonation reduced the microbial load to 0–8 CFU/mL without significantly altering the pH. However, qPCR analysis detected residual bacterial DNA, indicating the presence of viable but non-culturable (VBNC) cells or free DNA fragments. These findings confirm that combining nanofiltration and ozonation offers an effective, chemical-free strategy to improve the hygiene and stability of MWFs. However, conventional microbiological methods should be complemented by molecular tools for accurate contamination monitoring.