Bioremediation of a diesel fuel contaminated aquifer: simulation studies in laboratory aquifer columns

Abstract

The in situ bioremediation of aquifers contaminated with petroleum hydrocarbons is commonly based on the infiltration of groundwater supplemented with oxidants (e.g., 0 2 , N0 3 ) and nutrients (e.g., NH1, Pol-). These additions stimulate the microbial activity in the aquifer and several field studies describing the resulting processes have been published. However, due to the heterogeneity of the subsurface and due to the limited number of observation wells usually available, these field data do not offer a sufficient spatial and temporal resolution. In this study, flow-through columns of 47-cm length equipped with 17 sampling ports were filled with homogeneously contaminated aquifer material from a diesel fuel contaminated in situ bioremedia tion site. The columns were operated over 96 days at 12°C with artificial groundwater supple mented with 0 2 , N0 3 and POJ-. Concentration profiles of 0 2 , N0 3 , N0 2 , dissolved inorganic and organic carbon (DIC and DOC, respectively), protein, microbial cells and total residual hydrocarbons were measured. Within the first 12 cm, corresponding to a mean groundwater residence time of < 3.6 h, a steep 0 2 decrease from 4.6 to < 0.3 mg 1-1 , denitrification, a production of DIC and DOC, high microbial cell numbers and a high removal of hydrocarbons were observed. Within a distance of 24 to 40.5 cm from the infiltration, 0 2 was below 0.1 mg 1-1 and a denitrifying activity was found. In the presence and in the absence of 0 2 , n-alkanes were preferentially degraded compared to branched alkanes. The results demonstrate that: (1) infiltra tion of aerobic groundwater into columns filled with aquifer material contaminated with hydrocar bons leads to a rapid depletion of 0 2 ; (2) 0 2 and N0 3 can serve as oxidants for the mineralization of hydrocarbons; and (3) the modelling of redox processes in aquifers has to consider denitrifying activity in presence of 0 2 . ' Corresponding author.

Effect of Inoculation and Leaf Litter Amendment on Establishment of Nodule-Forming Frankia Populations in Soil

“…Six weeks after initiation of the incubation, soil of each of the four treatments was divided into 800-g (fresh weight) portions (n ϭ 15 each 3Ϫ , and Cl Ϫ ) were determined in pore water of soil samples collected (i) at the beginning of the study, (ii) after 2 weeks of incubation without plants, (iii) at planting time 6 weeks after initiation of the experiment, and (iv) at the end of the plant growth experiment, by ion chromatography (Dionex DX-100 ion chromatograph equipped with an IonPac AS4A-SC column; Dionex, Sunnyvale, Calif.) (21). Pore water was obtained as described by Nickel et al (36).…”

Engineered and subsequent intrinsic in situ bioremediation of a diesel fuel contaminated aquifer

“…During engineered in situ bioremediation, groundwater was extracted at S2 (May 1989-April 1991) or KB12 (May 1991-February 1994, respectively, supplemented with oxidants and nutrients and reinjected in S3. laboratory aquifer columns (Hess et al, 1996;Hunkeler et al, 1998), microcosms Bregnard et al, 1997) and enrichment cultures (Häner et al, 1995 showed that microorganisms from the contaminated aquifer were able to mineralize PHC under various redox conditions. Groundwater was pumped out of well S2 (May 1989-April 1991 or well KB12 (May 1991-February 1994and October 1994-May 1995 at a rate of 72-115 m 3 day À1 .…”

Engineered in situ bioremediation of a petroleum hydrocarbon-contaminated aquifer: assessment of mineralization based on alkalinity, inorganic carbon and stable carbon isotope balances

“…The processes in this aquifer were simulated in two independent Ž . laboratory aquifer column studies under aerobicrdenitrifying Hess et al, 1996 and Ž . anaerobic conditions Hunkeler et al, 1998 .…”

“…were postulated Table 3 . The scheme of processes had been successfully applied for Ž mass balances in laboratory aquifer columns and microcosms Bregnard et al, 1996;. Hess et al, 1996;Hunkeler et al, 1998 .…”