Stuart Lunn

Manipulation of density and viscosity for the optimization of DNAPL recovery by alcohol flooding

Abstract Laboratory experiments demonstrate that in situ recovery of pooled tetrachloroethene (PCE) from porous media may be accomplished more efficiently using multiple-step alcohol floods than with single alcohol floods. To optimize flooding efficiency while maintaining a low risk of downward DNAPL mobilization, a three-step flooding process is developed employing an isobutanol preflood, a composite alcohol mainflood, and a polymer solution postflood. The density and viscosity of these solutions are manipulated to prevent the onset and propagation of viscous and gravitational fingers, while maintaining phase behavior critical for efficient miscible NAPL displacement. An aqueous partitioning preflood solution of 10% by volume (10% v) isobutanol reduces the NAPL density in situ to approximately 1.00 g/ml by swelling the NAPL prior to miscible displacement induced by the mainflood. The composite alcohol mainflood, containing 65% v ethylene glycol and 35% v 1-propanol maintains miscibility while achieving neutral buoyancy and near stable displacement of the NAPL. Aqueous solutions of xanthan gum polymer efficiently displace the mainflood, reducing viscous fingering associated with waterfloods. Two-dimensional experiments using the multiple-step technique achieve 99.8% DNAPL mass recovery using a total of 0.45 pore volumes of alcohol, illustrating greater recovery efficiency than previous alcohol flooding formulations under comparable conditions.

Determination of ethanolamine, ethylene glycol and triethylene glycol by ion chromatography for laboratory and field biodegradation studies.

The determination of alkanolamines and glycols in groundwater and subsurface environments is essential for environmental assessment, remediation and monitoring for selected industrial sites. Monoethanolamine (MEA), ammonium, sodium, magnesium and calcium detection was performed using cation exchange chromatography (IC) with suppressed conductivity detection. Acetate, chloride, nitrite, nitrate, phosphate, sulfate and oxalate were monitored employing anion exchange chromatography with suppressed conductivity. Detection of ethylene glycol (MEG) and triethylene glycol (TEG) and ethanol was carried out using ion exclusion chromatography with pulsed amperometric detection. Effective determination of MEA, MEG and TEG in complex groundwater matrices without compound transformation offered improved monitoring capabilities. This study presents robust analytical tools for MEA, MEG and TEG determination in biodegradation studies. Using ion chromatography offered significant advantages for the analyses of groundwater samples and laboratory bioreactor monitoring.

Technical Note: Seeding Conditions of the Halophyte Atriplex Patula for Optimal Growth on a Salt Impacted Site

Salt-impacted soils resulting from oilfield brine spills are increasingly becoming a significant problem in oil-producing areas of Canada such as Alberta and Saskatchewan.The native halophyte Atriplex patula is being considered a potential species for phytoremediation of brine-impacted sites in these hemiboreal climactic zones. The objective of this study was to investigate the optimal seeding conditions under field conditions (with no irrigation) of A. patula for phytoremediation of salt from a brine-impacted site. Atriplex patula was identified in preliminary greenhouse trials to have one of the highest salt accumulations in relation to plant yields. Different seeding methods of A. patula were assessed in an attempt to achieve reproducible growth of this species. While plant yields for A. patula were improved on compacted soil by approximately 30–50%, growth was uneven with regard to density and height. The uneven growth may be due to seed quality and low precipitation during the field season, while improvements in plant yield on compact soil might be due to a lack of competition with other species.