Intrinsic Remediation Research Articles

The variability and intrinsic remediation of a BTEX plume in anaerobic sulphate-rich groundwater

Data from long-term groundwater sampling, limited coring, and associated studies are synthesised to assess the variability and intrinsic remediation/natural attenuation of a dissolved hydrocarbon plume in sulphate-rich anaerobic groundwater. Fine vertical scale (0.25- and 0.5-m depth intervals) and horizontal plume-scale (>400 m) characteristics of the plume were mapped over a 5-year period from 1991 to 1996. The plume of dissolved BTEX (benzene, toluene, ethylbenzene, xylene) and other organic compounds originated from leakage of gasoline from a subsurface fuel storage tank. The plume was up to 420 m long, less than 50 m wide and 3 m thick. In the first few years of monitoring, BTEX concentrations near the point of leakage were in approximate equilibrium with non-aqueous phase liquid (NAPL) gasoline. NAPL composition of core material and long-term trends in ratios of BTEX concentrations in groundwater indicated significant depletion (water washing, volatilisation and possibly biodegradation) of benzene from residual NAPL after 1992. Large fluctuations in BTEX concentrations in individual boreholes were shown to be largely attributable to seasonal groundwater flow variations. A combination of temporal and spatial groundwater quality data was required to adequately assess the stationarity of plumes, so as to allow inference of intrinsic remediation. Contoured concentration data for the period 1991 to 1996 indicated that plumes of toluene and o-xylene were, at best, only partially steady state (pseudo-steady state) due to seasonal groundwater flow changes. From this analysis, it was inferred that significant remediation by natural biodegradation was occurring for BTEX component plumes such as toluene and o-xylene, but provided no conclusive evidence of benzene biodegradation. Issues associated with field quantification of intrinsic remediation from groundwater sampling are highlighted. Preferential intrinsic biodegradation of selected organic compounds within the BTEX plume was shown to be occurring, in parallel with sulphate reduction and bicarbonate production. Ratios of average hydrocarbon concentrations to benzene for the period 1991 to 1992 were used to estimate degradation rates (half-lives) at various distances along the plume. The estimates varied with distance, the narrowest range being, for toluene, 110 to 260 days. These estimates were comparable to rates determined previously from an in situ tracer test and from plume-scale modelling.

Abstract: Evidence of Intrinsic Remediation at a Crude Oil Release Site 

Abstract: Evidence of Intrinsic Remediation at a Crude Oil Release Site 

Intrinsic remediation of a diesel fuel plume in Goose Bay, Labrador, Canada

This paper begins with a discussion of intrinsic remediation processes. Although intrinsic remediation involves biological, physical and chemical processes, the biological processes are often the most important. A field investigation consisting of sampling 102 groundwater and three surface water locations is described to characterize the intrinsic remediation occurring at a hydrocarbon contaminated site in Goose Bay, Labrador, Canada. Aerobic bioremediation, denitrification, ferrous iron reduction and sulphate reduction are occurring. Analysis of isopachs and isopleths resulted in the prediction of the assimilative capacity of groundwater. Intrinsic remediation can reduce the effects of free floating hydrocarbon, or free product. The effects of remediation can be optimized by adding nitrate saturated water to the groundwater regime.

Organic halogen, heavy metals and biological activities in pristine and pulp mill recipient lake sediments

In order to create a basis for prognosing future intrinsic remediation potential of past pollution by pulping industry, we analyzed biochemical activities and levels of pollution in sediments dated with 210Pb and 137Cs. A small pristine forest lake and a pulp mill recipient area of a large oligotrophic Lake Saimaa were test sites. Sediment concentration of EOX ranged from 40 to 130 μg Cl (g d.w.)−1 in the pristine lake and from 770 to 4700 μg Cl (g d.w.)−1 in the pulp mill recipient area and the C:Cl (w/w) ratio of sediment organic matter ranged from 2000 to 5100 and 42 to 230, respectively. The organic matter in 10 to 20 years old pulp mill recipient sediment was mainly of waste water origin. The activity gradients of β-glucosidase, butyrate-esterase, methane oxidation potential and endogenous respiration from surface to deeper layers were less steep in polluted than in pristine sediment. Methane oxidation potential was 120 μmol CH4d−1 (g C)−1 at the sediment surface of pristine lake sediment and 26 μmol CH4d−1 (g C)−1 at the polluted site, endogenous respiration rates of the surface sediment were 670 and 310 μmol CO2 d−1 (g C)−1, respectively. In the most polluted layer we found a depressed potential for methane oxidation, inhibition of phosphatase and butyrate-lipase activities and moderately increased induction ratio of β-galactosidase to phosphatase in the SOS-Chromotest strain E. coli PQ 37. The results suggest that at the concentrations observed these effects in the sediment were not due to heavy metals.

Implications of MTBE for Intrinsic Remediation of Underground Fuel Tank Sites

AbstractMTBE in groundwater has been shown to travel over 1,000 feet downgradient from its source in several comprehensive field studies conducted across North America. The biodegradability of MTBE is examined by summarizing all the significant literature on the subject and by detailing the findings of recent field investigations of MTBE transport. In Orange County, California, the persistence of MTBE is analyzed and statistical representations of source variability are presented. Regional and far field transport of MTBE in groundwater sourced from underground gasoline storage tanks are summarized in comprehensive tables of frequency and plume length. Estimates of source mass and duration allow for comparison of associated plume size. The conclusion reached after reviewing all the available literature on MTBE is that its biodegradability seems slight and the size of the plumes are surprisingly large. Intrinsic or natural attenuation remedies for MTBE merit close scrutiny.

Organic halogen, heavy metals and biological activities in pristine and pulp mill recipient lake sediments

In order to create a basis for prognosing future intrinsic remediation potential of past pollution by pulping industry, we analyzed biochemical activities and levels of pollution in sediments dated with 210Pb and 137Cs. A small pristine forest lake and a pulp mill recipient area of a large oligotrophic Lake Saimaa were test sites. Sediment concentration of EOX ranged from 40 to 130 μg Cl (g d.w.)−1 in the pristine lake and from 770 to 4700 μg Cl (g d.w.)−1 in the pulp mill recipient area and the C:Cl (w/w) ratio of sediment organic matter ranged from 2000 to 5100 and 42 to 230, respectively. The organic matter in 10 to 20 years old pulp mill recipient sediment was mainly of waste water origin. The activity gradients of β-glucosidase, butyrate-esterase, methane oxidation potential and endogenous respiration from surface to deeper layers were less steep in polluted than in pristine sediment. Methane oxidation potential was 120 μmol CH4 d−1 (g C)−1 at the sediment surface of pristine lake sediment and 26 μmol CH4 d−1 (g C)−1 at the polluted site, endogenous respiration rates of the surface sediment were 670 and 310 μmol CO2 d−1 (g C)−1, respectively. In the most polluted layer we found a depressed potential for methane oxidation, inhibition of phosphatase and butyratelipase activities and moderately increased induction ratio of β-galactosidase to phosphatase in the SOS-Chromotest strain E. coli PQ 37. The results suggest that at the concentrations observed these effects in the sediment were not due to heavy metals.

Intrinsic bioremediation of fuel contamination in ground water at a field site

A spill of gasoline occurred at an automobile service station in 1986. Oily phase residue in the subsurface has continued for the past 8 yr to release water soluble fuel hydrocarbons into the aquifer. The site was characterized for implementation of intrinsic remediation. The subsurface was a beach sand with sea shell fragments. The water table was near 1.3 m below ground surface. Surface dimensions over the plume were about 200 m downgradient and 60 m in width. Three points to coincide with direction of ground-water flow were selected in the plume for water quality assessments. Both methane and trimethylbenzene were used as surrogate tracers to normalize loss of contaminants. Aerobic respiration and methanogenesis accounted for most biodegradation obtained. Assimilation capacities of dissolved oxygen, ferrous iron, and methane distributions when compared to BTEX concentrations showed that the ground water has sufficient capacity to degrade all dissolved BTEX before the plume moves beyond 250 m downgradient. Evidence obtained from loss of contaminants, geochemistry, and microbial breakdown chemicals showed that intrinsic bioremediation technology would be a viable option to restore the site.

Microbial biomass in a shallow, urban aquifer contaminated with aromatic hydrocarbons: analysis by phospholipid fatty acid content and composition.

The city of Perth contains a number of sites that have been contaminated with hydrocarbons due to leakage from petroleum underground storage tanks. Microbial biomass in groundwater and sediment cores from above and below the water table, and from within and outside a plume of hydrocarbon contamination, was examined using phospholipid fatty acid methyl ester analysis. Microbial numbers, calculated from the phospholipid content, ranged from 0.9 x 10(6) to 7.8 x 10(6) 'Escherichia coli equivalent cells' g-1 dry wt of sediment. Over 96% of the microbial biomass was attached to the sediment and the proportion of attached cells did not decrease within the plume of contaminants. The amount of biomass within aquifer samples seemed to be related more to the proximity of the rhizosphere to the shallow aquifer, and other unknown urban inputs, rather than to the effects of the plume of contaminants. Fatty acids common to many bacterial groups dominated within the plume, and as such the analyses gave limited insight into microbial community structure. For site assessment of intrinsic remediation of shallow aquifers in urban areas, estimates of microbial biomass may not provide information that is readily applicable to plume management.

Remediative Capacity of Crude Oil-polluted Soil After Exposure to Poultry Manure and Phosphate Minerals

This study investigated the impact of two soil amendments (poultry manure and phosphate rock minerals) on the intrinsic remediation capacity of a crude oil-contaminated soil. Well drained top soil (0-10 cm) was polluted with crude oil at the rate of 0.02mL/g of soil and amended with phosphate rock (PR) and poultry manure in three batches at 20 g, 30 g, 40 g and 50 g per 500 g of soil respectively in plastic bowls. Soil samples were collected from plastic bowls for physicochemical, microbiological, biodegradability and total hydrocarbon contents analyses. Results revealed improvement in physicochemical parameters in pH, total nitrogen and phosphorus of 7.00-7.50, 0.12-0.22 %, and 13.20- 65.42 mg/100 g after remediation against 4.30, 0.02 % and 6.05 mg/100 g recorded in day zero respectively. Bacillus subtilis (2.01), Pseudomonas aeruginosa (1.94), Mucor mucedo (2.47) and Penicillium notatum (2.43) had high biodegradation potential (NTU). The remediation efficiency of total hydrocarbon content after remediation was enhanced by two factors; increased concentrations of amendments of 50 g of poultry manure (4.62 mg/100 g; 66.45 %) and phosphate rock (0.33 mg/100 g; 97.60 %); And by application of combined amendments of both poultry manure and phosphate rock (0.19 mg/100 g; 98.62 %) compared to control (8.46mg/100 g; 38.56 %). Poultry manure and phosphate rock amendments enhance bioremediation efficiency in clean-up of crude oil polluted site and obviously a contamination free environment is a healthy and safe environment for all.Keywords: Bioremediation, Poultry manure, Phosphate mineral, Hydrocarbon content