In-situ surfactant/surfactant-nutrient mix-enhanced bioremediation of NAPL (fuel)-contaminated sandy soil aquifers.
BACKGROUND
Contamination of soils, aquifers and groundwater by nonaqueous phase liquid (NAPL) pollutants constitutes a major environmental issue of concern, worldwide. The residual (biodegradation-resistant) hydrophobic fuel hydrocarbons entrapped in the soil porous matrix, possess a particular bioremediation challenge due to their becoming virtually immobile, nor desorbable, or water dispersible. Consequently, they are not available as substrates to the micro-organism-based biodegradation.


METHODS
Our research involves the development of economically feasible, surfactant/surfactant-nutrient mix (SSNM)-enhanced bioremediation methodologies for sustainable, in situ bioremediation of fuel-contaminated aquifers. This requires, methodologically, (a) the optimization, via in vitro 'flow' (columns) lab experiments and screening processes, of an effective mixture for the intended SSNM-enhanced bioremediation; and (b) the study of the combined effect of the optimized SSNM on the solubilization/mobilization and biodegradation of NAPL (fuel) in in vitro site/aquifer-simulated bioremediation.


CONCLUSIONS
The essence of our findings: (1) kerosene's maximum enhanced mobilization - f = 3.6, compared with that of deionized water, was achieved with an SSNM having the composition of linear alkylbenzene sulfonate (LABS): coco-amphodiacetate (containing N): surfactant-nutrient X (containing both N and P) = 0.15: 0.15: 0.05 g/L, respectively; (2) 62-64% of the initial amount of kerosene in the initially saturated soil matrix, 'packed' in a column, has been eluted from it during approximately 30 days, compared with 68% of kerosene biodegradation in 'vessel' settings, in 21 days.


CONCLUSIONS
(1) The indigenous microorganisms present in th vadose zones of fuel-contaminated sandy soil aquifers are potentially capable of unassisted removal of approximately 80% of the initially contained fuel (kerosene), during a period of about 42 days; (2) the major effects of the SSNM addition are (a) enhanced mobilization of the bulky NAPL; and (b) enhanced desorbtion/ solubilization/dispersion of the entrapped NAPL which, in turn, facilitate their enhanced biodegradation.


CONCLUSIONS
Our findings suggest that pre-optimized, biodegradable SSNM is essential for surfactants-based bioremediation of NAPL-contaminated aquifers, in order to make this in-situ methodology both technologically and economically feasible.
Zoller
Uri
U
Faculty of Science and Science Education-Chemistry, Haifa University-Oranim, Kiryat Tivon 36006, Israel. uriz@research.haifa.ac.il
Reznik
Alla
A
D001673:Biodegradation, Environmental; D007648:Kerosene; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013501:Surface-Active Agents / Q000737:chemistry*; D014050:Toluene / Q000032:analysis / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
D007648:Kerosene; D012987:Soil; D012989:Soil Pollutants; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D014050:Toluene