Transport of E. coli in aquifer sediments of Bangladesh: Implications for widespread microbial contamination of groundwater

Abstract

Fecal bacteria are frequently found at much greater distances than would be predicted by laboratory studies, indicating that improved models that incorporate more complexity are might be needed to explain the widespread contamination of many shallow aquifers. In this study, laboratory measurements of breakthrough and retained bacteria in columns of intact and repacked sediment cores from Bangladesh were fit using a two-population model with separate reversible and irreversible attachment sites that also incorporated bacterial decay rates. Separate microcosms indicated an average first order decay rate of 0.03 log10 / day for free bacteria in both the liquid phase and bacteria attached to the solid phase. Although two-thirds of the column results could be well fit with a dual deposition site, single population model, fitting of one third of the results required a two-population model with a high irreversible attachment rate (between 5 and 60 hr-1) for one population of bacteria and a much lower rate (from 5 hr-1 to essentially zero) for the second. Inferred attachment rates for the reversible sites varied inversely with grain size (varying from 1 - 20 hr-1 for grain sizes between 0.1 and 0.3 mm) while reversible detachment rates were found to be nearly constant (approximately 0.5 hr-1). Field simulations based on the fitted two-population model parameters predict only a two-fold reduction in fecal source concentration over a distance of 10 m, determined primarily by the decay rate of the bacteria. The existence of a secondary population of bacteria with a low attachment rate might help explain the observed widespread contamination of tubewell water with E. coli at the field site where the cores were collected, as well as other similar sites.

Transport of Pathogen Surrogates in Soil Treatment Units: Numerical Modeling

“…Model fits were good with R 2 values ranging from 0.97 to 0.99. The dispersivity value calculated by CXTFIT 2.1 was approximately 0.289 cm, which is typical for these types of experiments, and is consistent with the range of values (0.06 to 0.816 cm) reported by others [38][39][40][41][42][43]. Next, the hydraulics of the HYDRUS model domain was calibrated using the conservative tracer breakthrough curves (BTC).…”

Mimicking filtration and transport of rotavirus and adenovirus in sand media using DNA-labeled, protein-coated silica nanoparticles

“…Understanding of the attachment-detachment kinetics has important implication in risk assessment. Detachment is considered a major reason for the widespread microbial contamination of some shallow groundwater and allows microbial contaminants to move much further into an aquifer (Feighery et al, 2013;Knappett et al, 2014). A constantly slow release of viruses from previously attached in the porous media will lengthen the contamination duration, and a sudden release of microbial contaminants due to a change of hydraulic conditions (e.g.…”

ZVI (Fe0) desalination: catalytic partial desalination of saline aquifers

“…The elevated Eh nano-redox conditions (> 0.7 V) within the ZVI intraparticle porosity are suitable for the growth of Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus (e.g., Deza et al 2005). These species are natural constituents of many shallow aquifers (e.g., Ridgway et al 1990;Hossain and Anwar 2009;Feighery et al 2013;Penny et al 2015). The sheltered intra-particle nano-environment will, in some aquifers, result in colonies of these species growing within the ZVI during desalination.…”