Effects of slight variations in nutrient loadings on pore plugging in soil columns

Application of Biobarriers for Groundwater Containment at Fractured Bedrock Sites

“…In different environments, numerous studies have shown the influence of nutrients on the structure of biofilms, on their composition in EPS, and on the resulting bioclogging (Linton et al, 1987;Jennings et al, 1995;Stoodley et al, 1999). Using indigenous bacteria from a hypersaline oil reservoir, Davey et al (1998) found that the selective plugging (> 90 percent reduction in permeability) of sandstone (0.3 m·d -1 < K < 3 m·d -1 ) was superior when soluble cornstarches, such as maltodextrins, were used, compared with simple sugars, such as molasses.…”

Transport of Gellan Gum Microbeads in Soil Columns of Various Grain Size Distributions

“…In the present study, 70% of microbeads were recovered at a distance of 50 cm in column E packed with 0.25-2 mm sand. Although a direct comparison is not warranted since the experimental conditions of the present study differed from those involved with free bacteria (Taylor and Jaffé, 1990;Jennings et al, 1995;Hendry et al, 1999), the extensive transport of microbeads through the granular media observed in this study presumes that encapsulation of cells within polymeric gel carriers would avoid cell sorption to grain surfaces. This enhances the potential for the use of encapsulated cells for subsurface remediation applications.…”

“…However, the augmented cells may be limited in their biodegradation capacity for various reasons including the inhibitory effect of high concentrations of the contaminant, predation by protozoa, and insuffi cient transport of microorganisms through the porous matrix of the contaminated aquifer (Goldstein et al, 1985). During transport, microbial cells attach to available grain surfaces in the form of microcolonies and produce exopolysaccharides, leading to formation of a plugging biofi lm that can cause a signifi cant decrease in pore permeability (Taylor and Jaffé, 1990;Jennings et al, 1995), and an early interruption in the injection process.…”

In Situ Bioremediation of Carbon Tetrachloride: Field Test Results

“…One of the primary constraints to the choice of the nutrient feeding strategy for this demonstration was avoiding biofouling of the nutrient injection well. Previous simulations (Clement et al, 1996;Shouche et al, 1993), laboratory experiments (Jennings et al, 1995;Peyton, 1996), and field tests (Semprini et al, 1991) have shown that improper addition of electron donor and acceptor will result in preferential growth at the injection point. However, the use of temporally separated pulses of electron donor and acceptor has been shown to form a more even distribution of biomass throughout a flow field (Clement et al, 1996;.…”

“…In addition, nutrient addition strategies should be formulated to prevent preferential growth of microorganisms at the injection well, leading to both poor contaminant destruction characteristics and wellbore biofouling. Previous results have shown rapid aquifer plugging using denitrifiers under continuous electron donor and acceptor feeding conditions (Jennings et al, 1995). Conversely, a variety of nutrient addition strategies involving discrete pulses of substrate have been reported to maintain recirculation conditions without significant biofouling (Peyton, 1996;Shouche et al, 1993).…”