Bacterial Retention in Lipopolysaccharide Coated Silica Sand

Abstract

Wastewater reclamation has been widely practiced in agriculture. When reclaimed wastewater is used for irrigation, among other requirements, it is important that the pathogenic bacteria are removed. Consequently, technologies such as immobilization or sorption barriers have been developed. To enhance the removal efficiency, biopolymers have been introduced to amend these immobilization or sorption barriers. In this study, removal of pathogenic bacteria by lipopolysaccharide (LPS)‐amended barriers was investigated by means of laboratory column experiments. Two typical gram‐negative pathogenic bacterial strains of Escherichia coli and Pseudomonas fluoresences and one gram‐positive bacterial strain of Streptococcus mitis were selected as the model bacteria in this research. Bacterial adhesion to uncoated and LPS‐coated silica sand was correlated to their interaction free energies. Both E.coli, P. fluorescens, and S. mitis had negative interaction free energies with silica sand, demonstrating their adhesion potentials to silica sand. After LPS coating, bacterium‐sediment interaction free energies decreased (negatively increased), and consequently, bacterial retention increased. Bacterial deposition coefficient in silica sand corresponded to their interaction free energies with silica sand. This study demonstrated that bacterial retention in porous media was determined by their interactions with the sediments, which could be predicted based on independently determined bacterial and medium physicochemical surface properties.