Microfiltration membranes are widely employed for water/wastewater treatment. Although integral microfilters achieve virtually complete removal of protozoa and bacteria, the same cannot be said for viruses. For this reason, we are investigating mechanisms of colloid transport across porous microfiltration membranes. Specifically, the objectives of this poster presentation are to quantify the effects of virus diameter vis-à-vis the pore diameter as well as virus and pore zeta potential on removal. This will serve as the basis for my undergraduate thesis. The removal of two bacterial viruses (MS2 and PRD1) and two spherical silica particles by track-etched membranes of various pore diameters (0.05 to 1.2 microns) were measured in the dead-end mode with vigorous stirring to reduce concentration polarization effects. Results are shown in Figure 1 for experiments performed at relatively high ionic strengths where the zeta potential was close to zero. As seen, our data quantitatively agree with a simple model based on hindered convection of spherical colloids through cylindrical pores. This demonstrates that the increased resistance to passage is well-captured by steric and hydrodynamic interactions between the particle and the pore wall in the absence of any long-range interactions. We also hypothesized that repulsive pore wall-particle interactions would increase removal. Experiments are currently underway to measure variations in biocolloid removal as a function of ionic strength (10-4–0.1 M), pH (3-9), and electrolyte type (KCl, CaCl2, & LaCl3). Preliminary measurements of the zeta potentials of colloidal silica measured using a Litesizer (Anton Paar) are shown in Figure 2. Similar measurements are being made for viruses and membrane pores (SurPASS). Laboratory experiments at Texas A&M will be interpreted using mathematical models currently under development at Clarkson University, which will also be presented.

Pore size and zeta potential effects on colloid removal by clean microfiltration membranes

255th National Meeting (2018)

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