Numerical modeling analysis of hydrodynamic and microbial controls on DNAPL pool dissolution and detoxification: Dehalorespirers in co-culture

Abstract

Dissolution of dense non-aqueous phase liquid (DNAPL) contaminants like tetrachloroethene (PCE) can be "bioenhanced" via biodegradation, which increases the concentration gradient at the DNAPL-water interface. Model simulations were used to evaluate the impact of ecological interactions between different dehalorespiring strains and hydrodynamics on the bioenhancement effect and the extent of PCE dechlorination. Simulations were performed using a twodimensional coupled flow-transport model, with a DNAPL pool source and two microbial species, Dehalococcoides mccartyi 195 and Desulfuromonas michiganensis, which compete for electron acceptors (e.g., PCE), but not for their electron donors. Under biostimulation, low v x conditions, Dsm. michiganensis alone significantly enhanced dissolution by rapidly utilizing aqueous-phase PCE. In co-culture under these conditions, Dhc. mccartyi 195 increased this bioenhancement modestly and greatly increased the extent of PCE transformation. Although Dsm. michiganensis was the dominant population under low velocity conditions, Dhc. mccartyi 195 dominated under high velocity conditions due to bioclogging effects.

Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

“…Experimental work has documented that the dissolution process is affected by heterogeneity, NAPL saturation, and contact with flowing water. Furthermore, biodegradation can change the concentration of dissolved solutes affecting the concentration gradient driving interphase mass transfer [e.g., Essaid et al ., ; Wesseldyke et al ., ].…”

“…Models of biodegradation published in WRR quickly obtained a level of sophistication beyond what could be tested with field data. It is exciting that methods for characterizing microbial consortia at relevant scales are now becoming available to test these models and provide new insights of microbial reaction at the pore scale [ Wesseldyke et al ., ]. Understanding of chemical reactions in groundwater will continue to be relevant to management of groundwater resources [ National Research Council , ], and future progress will build on the foundation of the work published in WRR .…”