Attachment of Escherichia coli to fine sediment particles within construction sediment basins

The conventional best management practice of sediment basins may create a reservoir for pathogenic bacteria. The fine particles that enter these basins have been shown to provide protection for bacteria; the small pores of clays and silts minimize predators and block sunlight. Therefore, while these basins decrease sediment loadings to water bodies downstream, they may introduce harmful levels of pathogenic bacteria into surface waters. In addition to causing human health risks, high bacteria levels alter natural biological makeup of downstream ecosystems. This paper describes the attachment of Escherichia coli to various particle sizes in construction site sediment basins. Five sediment basins, located in Anderson, South Carolina were sampled after rain events to explore trends that exist between various particle sizes and E. coli densities. Results provide evidence to suggest that sediment basins are a reservoir for pathogenic bacteria. Data showed that most E. coli attached to smaller particles with diameters less than 0.004 mm. These particles do not settle out of the water column quickly and are often passed through the basin during intense storms. Consequently, high levels of bacteria are passed to downstream waters. This research provides considerable evidence that the clays and silts within man-made construction basins can cause detrimental effects to South Carolina surface waters. With this knowledge, better stormwater management practices may be developed with the goal of remediating impaired surface waters of South Carolina.