Role of sand size on bacterial retention in biochar-amended sand filters

Abstract

The addition of biochar to sand columns can enhance the retention of bacteria and thus may provide a management strategy for removing bacteria from tile-drainage waters. In this study, the role of sand size as a factor in controlling microbial retention in biochar-amended sand columns was investigated. Laboratory column experiments were conducted to quantify the removal of two bacterial isolates (E. coli and Salmonella) and polystyrene microspheres in 10-cm-long columns packed with clean sand of three different sizes (0.25, 0.71, and 1.19 mm) at four biochar concentrations (0%, 5%, 10%, and 15%). Sorption studies were also performed to help identify the relative roles of sorption and physical straining on the removal of bacteria and microspheres within the columns. For the large sand, the log 10 removal values (LRV) for E. coli increased from 0.22 to 0.49 for the 0% and 15% biochar concentrations, respectively, while LRV for Salmonella increased from 0.19 to 0.68. For the small sand, increasing biochar concentration from 0% to 15% increased LRV from 0.11 to 1.9 for E. coli and from 0.20 to 4.6 for Salmonella. In comparison, LRV for microspheres in the 15% biochar columns was only minimally higher than the unamended columns for all three sand sizes. Results from the sorption studies show that high sorption coefficients generally correlated with high LRV indicating that sorption rather than physical straining was the primary mechanism of retention in the columns. Results from this study further our understanding of bacterial retention in biochar-amended porous media. Article Highlights • Sand size can affect microbial retention in biochar-amended sand • Effect of sand size on bacterial retention varied depending on bacterial strain • Minimal retention of microspheres within biochar-amended sand columns indicates minimal physical straining

Adsorption of pharmaceuticals from aqueous solutions using biochar derived from cotton gin waste and guayule bagasse

“…Research on biochar as a potential filter media for urban stormwater runoff demonstrated that biochar filters effectively remove total suspended solids, heavy metals, nutrients, polycyclic aromatic hydrocarbons, and E. coli (Mohanty and Boehm 2014;Reddy et al 2014). Bolster (2019) demonstrated that adding biochar to sand columns enhanced the removal of bacterial isolates E. coli and Salmonella, with sorption being the primary mechanisms for bacteria removal. Studies have also reported the potential use of biochar as an adsorbent for the treatment of agricultural wastewater effluents.…”

Influence of Simplified Microbial Community Biofilms on Bacterial Retention in Porous Media under Conditions of Stormwater Biofiltration

“…The effect of physical partitioning of surface area might be similar to that of mixing porous media with different surface characteristics, in which bacterial retention efficiency of mixtures changes monotonically with the increase of the mixing ratio of a constituent medium until reaching the retention efficiency of that medium. For example, increasing the concentration of biochar mixed in porous media monotonically increased the bacterial retention efficiency ( 58 , 59 ). In the present study, we observed that the increase of the abundance ratio of SW3 and PAO1 generally enhanced the E. coli retention efficiency in SW3+1 and PAO1+SW1 columns until reaching the retention efficiency in PAO1-only or SW3-only columns.…”