Survival of Escherichia coli in stormwater biofilters

Abstract

Biofilters are widely adopted in Australia for stormwater treatment, but the reported removal of common faecal indicators (such as Escherichia coli (E. coli)) varies from net removal to net leaching. Currently, the underlying mechanisms that govern the faecal microbial removal in the biofilters are poorly understood. Therefore, it is important to study retention and subsequent survival of faecal microorganisms in the biofilters under different biofilter designs and operational characteristics. The current study investigates how E. coli survival is influenced by temperature, moisture content, sunlight exposure and presence of other microorganisms in filter media and top surface sediment. Soil samples were taken from two different biofilters to investigate E. coli survival under controlled laboratory conditions. Results revealed that the presence of other microorganisms and temperature are vital stressors which govern the survival of E. coli captured either in the top surface sediment or filter media, while sunlight exposure and moisture content are important for the survival of E. coli captured in the top surface sediment compared to that of the filter media. Moreover, increased survival was found in the filter media compared to the top sediment, and sand filter media was found be more hostile than loamy sand filter media towards E. coli survival. Results also suggest that the contribution from the tested environmental stressors on E. coli survival in biofilters will be greatly affected by the seasonality and may vary from one site to another.

Bacteria Removal from Stormwater Runoff Using Tree Filters: A Comparison of a Conventional and an Innovative System

“…However, in winter both filters did not meet the removal standards as removal for the CTF was measured at 71.3%˘35.5% compared to 77.3%˘32.0% for the ITF. Similar removal capabilities have been observed in other studies that also rely on bacteria straining and removal through filtration [19,40] Comparing the E. coli removal by season, lower removal values were observed in the winter compared to the summer (Table 4, Figure 4). In both seasons the removal of E. coli is slightly higher in the ITF compared to the conventional TF (Table 4).…”

Indicator and Pathogen Removal by Low Impact Development Best Management Practices

“…Many abiotic and biotic conditions such as sunlight/Ultraviolet (UV) radiation, temperature, osmotic stress, moisture content, nutrient availability, and biotic competition can affect persistence of microbes in the environment [11,18,19]. Sunlight/UV exposure and moisture content were found to be important for E. coli survival in biofilter surface layers, while temperature and the presence of indigenous microbial communities greatly affected E. coli at all biofilter depths [20]. Rippy [12] summarized two competition mechanisms by which indigenous microbial community in the biofilters could impact fecal indicator bacteria die-off.…”

Meeting the criteria: linking biofilter design to fecal indicator bacteria removal

“…Salinity and pH effects may be most notable for EC, as ENT are halotolerent and can survive at pH 4 to 10 . EC and ENT are both sensitive to soil moisture, although the magnitude and direction of response varies . Temperature effects on FIB may also vary, with cold frequently reported to enhance survival .…”