Impact of bacterial streamers on biofouling of microfluidic filtration systems

Abstract

We investigate the effect of biofouling in a microfluidic filtration system. The microfluidic platform consists of cylindrical microposts with a pore-spacing of 2 m, which act as the filtration section of the device. One of our key findings is that there exists a critical pressure difference above which pronounced streamer formation is observed, which eventually leads to rapid clogging of the device with an accompanying exponential decrease in permeate flow. Moreover, when streamers do form, de-clogging of pores also occurs intermittently, which leads to small time scale fluctuations [O(10 s)] superimposed upon the large time scale [O(10 min)] clogging of the system. These de-clogging phenomena lead to a sharp increase in water permeation through the microfluidic filtration device but rates the water quality as biomass debris is transported in the permeate. Streamer-based clogging shares similarities with various fouling mechanisms typically associated with membranes. Finally, we also show that the pH of the feed strongly affects biofouling of the microfluidic filtration system.

Investigating fouling at the pore-scale using a microfluidic membrane mimic filtration system

“…When a mixture like particle laden polymer (PAM(0.2%):PS(0.2%) = 1:4) is filtered through our MMM system, a filamentous compliant structure was formed at downstream of the pillars. This structure is called the ‘colloidal streamer’ 41 . Figure 2(d) shows colloidal streamer fouling, which is the second kind of downstream fouling captured at 120 min of filtration at 689 mbar pressure.…”

A microfluidic platform for characterizing the structure and rheology of biofilm streamers

“…10,11 Streamlining allows biofilms to minimize drag, which can consequently withstand stronger flows and effectively colonize different flow environments. Streamer formation has been observed on obstacles in a flow path, such as porous media and medical devices, [12][13][14][15][16] or on objects moving in a fluid, like marine particles, rising oil droplets, or sinking marine snow in the ocean. 17,18 Thus, streamers appear to play a crucial role both in medical and environmental settings.…”

The structural role of bacterial eDNA in the formation of biofilm streamers

“…When the viscoelastic biofilm matrix is subjected to the hydrodynamic forces generated by flows, biofilms can take the form of long filamentous suspended structures, the streamers, which increase the carrying capacity of biofilms in natural ecosystems ( 22 ). Indeed, their localization within the bulk fluid flow, in contrast to the thin-film morphology of surface-associated biofilms, confers streamers a greater impact on the uptake of microorganisms and debris flowing by and clogging ( 23 , 24 ). Structures morphologically similar to streamers can also be formed by abiotic materials in flow, as shown by flowing a suspension of polyacrylamide and polystyrene particles through a porous structure ( 25 ).…”