A closer look at the role of biofilms in water filtration: Bridging microscopic insights with system performance

Biofilm processes are crucial in water filtration, safeguarding public health. They affect filter media's hydraulic properties and particle removal efficiency. Traditional studies use large samples, lacking internal mechanism observation. Microfluidics replicate real filter grains for direct biofilm growth observation, particle transport analysis, and hydraulic property changes over time. Coupled with two methods of advanced fluorescent microscopy and confocal laser scanning, the maturation of biofilm and the simultaneous removal of particles during experiments were precisely observed. The results demonstrated that biofilm formation created preferential flow paths, reducing media porosity from 36 % to 9 %, impacting conductivity and particle transport behavior. Particle velocity increased from 4.58 mm/s in clean models to 7.46 mm/s in clogged ones, with tortuosity rising from 1.24 to 1.30. The cumulative effect of these processes was an evident increase in the log 10 removal efficiency of the filters, which improved from 0.17 in clean conditions to 1.91 in the presence of biofilm. The results from this study lay foundations for precise interpretation of particle transport and removal by water filters and optimizing filter efficiency and treatment processes. Particles tortuosity increases by biofilm growth due to bypassing bio-clogged pores. • Biofilm growth increases surface roughness, enhancing particle removal rates. • Altered pore size distribution from biofilm growth enhances the straining mechanism. • Creation of preferential flow paths by biofilm growth reduces particle arrival time. • Biofilm growth leads to more attached particles and increased particle velocity.