Click here to download the EISB case study presentation.

Reference: Carey, G.R., 2015. 4-hour short course entitled: “Using the NAPL Depletion Model for Estimating Timeframes for Natural and Enhanced Attenuation”. Presented at the Third International Symposium on Bioremediation and Sustainable Environmental Technologies, Miami, Florida, May 18, 2015.

ABSTRACT:

The performance of enhanced in-situ bioremediation (EISB) is dependent on the degree to which substrates, and injected microbes if applicable, are delivered to within close proximity to the NAPL-water interface.  One of the factors which may reduce the effectiveness of mass destruction with EISB is potential clogging of pore spaces in the vicinity of this NAPL-water interface, either through bacterial growth or methane gas generation.  One of the questions associated with EISB performance is the dissolution enhancement factor, which represents the ratio of the dissolution rate (grams per day) for the EISB alternative relative to a scenario involving natural dissolution.

Sleep et al. (2006) present laboratory experiments that involved detailed monitoring of two test cells: one with EISB (substrate injection combined with bioaugmentation) in a DNAPL (TCE) zone, and one with natural dissolution.  The NAPL Depletion Model (NDM) was used to simulate both of these laboratory experiments, and to estimate the time-varying dissolution enhancement factor for the EISB experiment.  NDM was also used to simulate the influence of methane gas clogging of pore spaces which likely resulted in a substantial reduction in the NAPL dissolution rate during the later portion of the EISB experiment.