Influence of Biofilm and Calcium on Transport of Lead Phosphate Nanoparticles through Solid Block Activated Carbon Media

Solid block activated carbon (SBAC) is a common material used in many point-of-use (POU) filters. Previous work on POU filters has focused primarily on one type of contaminant; however, inorganic contaminants, organic contaminants, and biogenic products from microorganisms co-occur. We examined the interactions of Pb nanoparticles and biofilm in a SBAC environment. Filters with and without bacteria growing on the surface of the SBAC media were challenged with suspensions of Pb phosphate nanoparticles containing various aqueous concentrations of calcium (0 mM, 0.5 mM, and 1.5 mM). Filters with bacteria and 1.5 mM Ca(II) had the highest Pb removal efficiency (72–82%). Biofilm presence and the addition of Ca(II) resulted in better removal of Pb phosphate nanoparticles. To understand the impact of particle size and electrostatic interactions on Pb removal, we measured the hydrodynamic diameter and zeta potential of Pb nanoparticles with varying concentrations of Ca(II) and dissolved biomass. Fast aggregation of nanoparticles in the presence of Ca(II) was strongly correlated with Pb removal by filters. Particle aggregation in the presence of dissolved biomass was moderately correlated with Pb removal in biofilm-coated filters, suggesting that investigation of additional mechanisms is needed to fully explain the increase in Pb removal from biofilm-coated filters.