Long-term survival of Escherichia coli in lightweight aggregate filter media of constructed wastewater treatment wetlands

Abstract

A laboratory scale experiment on the survival of Escherichia coli in samples of filter media from a horizontal subsurface flow constructed wetland treating domestic wastewater was performed. A concentration of E. coli was examined in samples collected from a wetland filter filled with lightweight aggregates (LWA). All samples testing positive for E. coli contamination were used to examine the effect of storage time on the survival of E. coli at three temperature regimes: cold (4°C), mild (10°C) and warm (22°C). It was found that the mild storage condition favoured the growth and survival of E. coli in the tested LWA media. The growth in samples of the uppermost layer of the media lasted for 5.5 months, during which E. coli reached a maximum concentration of 6.4×10(3) MPN/100 g dry matter in the media. It was also observed that E. coli had a greater capacity to survive for extended periods of time in samples collected from the upper layer of the LWA filter compared to samples taken from the deeper layers. The survival of E. coli in the shallowest samples of the wetland filter was remarkably long and unexpected, lasting for a period of over 14 months.

Effects of temperature, storage time and pH on survival of Escherichia coli in source‐separated yellowwater

“…). This was previously noticed in an earlier experiment on the faecal pollution of filter materials treating domestic wastewater, which revealed the highest and longest survival rates of E. coli in samples stored at 10°C (Paruch ). Further evidence of the impact of mild storage conditions on the survival of E. coli was provided by the studies of Chandran et al .…”

“…The contaminated materials were further examined at different times (18 samples in total) as it was presumed that E. coli can survive several days in stored yellowwater. This presumption was based on the outcomes from related experiments and literature references that revealed the long‐term survival of E. coli in materials impacted by faecal pollution (Paruch and references therein).…”

Changes in Microbial Quality of Irrigation Water Under Different Weather Conditions in Southeast Norway

“…The FIB characterized by E. coli was examined using the Colilert system which does not require any confirmation steps and demonstrates the highest accuracy in the detection of E. coli in comparison to other standard methods used (Paruch 2011). Regarding the examination of parasitic protozoa, the analytical method results in considerable losses, such that the actual contamination of the water was probably higher than that described in these results.…”

“…Although the presence of FIB indicates recent faecal contamination, the bacteria may also survive in soil sediments, sand and filter materials (Patz et al 2008;Whitman et al 2008;Paruch 2011), be re-suspended during precipitation events and flushed with subsequent runoff directly into water bodies. Therefore, diffuse pollution from agricultural runoff may also be considered to represent faecal contamination of surface waters.…”

“…E. coli concentrations were examined using the Colilert 18/Quanti-Tray®2000 Method (IDEXX Laboratories Incorporated, Westbrook, Maine, USA). The scientific background of this method has been described elsewhere in greater detail (Paruch 2011).…”