Scrap zero-valent iron particles or iron-rich drinking water treatment residues have shown the potential to remove pollutants such as phosphate and pathogens in stormwater biofilters. However, their sorption capacity may become exhausted in the presence of dissolved organic carbon (DOC), which is ubiquitous in stormwater and can also leach from organic amendments typically used in biofilters. Using both batch and column experiments, we exposed iron filings to DOC and found that adsorption of 1 mg of DOC per 1 g of iron filings reduces its bacterial removal capacity by 8%. The result is attributed to the alteration of the surface charge of iron by DOC and blocking of adsorption sites. The presence of compost completely diminished the initially higher adsorption capacity of 3% of iron-only columns compared to iron-compost columns, whereas the addition of 10% iron maintained consistently higher removal, indicating the amount of iron is critical for their effectiveness in biofilters. The presence of iron also limits the growth of<i> E. coli</i> trapped in columns during the drying period between consecutive rainfalls. Collectively, these results indicate that although iron filings may lose some of their capacity in the presence of DOC, the addition of a sufficient amount could still provide an advantage for pathogen removal. The study helps inform the guideline for iron media use in stormwater biofilters and provide an empirical model to predict the reduction in adsorption capacity of iron filings based on dissolved organic carbon in the stormwater influent.

Is organic amendment a culprit in lowering bacterial removal capacity of iron in stormwater biofilters?

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.