Diffusion chamber method for in situ measurement of pathogen inactivation in groundwater

A method has been developed to measure pathogen inactivation in groundwater in situ by installing diffusion chambers in wells. This method has advantages over others in terms of utility, reduction of artefacts, and the ability to accommodate porous media. The diffusion chambers have been tested in the laboratory for their ease of sterilization, and the effect of pressure on leakage. Exchange processes across the membranes were examined, and the effective diffusion coefficients for movement of KCl through two different pore-size membranes are given. An expression to account for the dilution in microbial concentrations due to periodic subsampling from the chamber has been determined. Finally, an example in a field application of the use of diffusion chambers in situ provided inactivation rates for Enterococcus faecalis from chambers with and without a porous medium.