Bioremediation Of Diesel-contaminated Soil Research Articles

Investigating the influence of sulphur amendment and temperature on microbial activity in bioremediation of diesel-contaminated soil

This study investigated the effectiveness of incorporating sulphur (S) with nitrogen (N) and phosphorus (P) for enhancing microbial activity in diesel-contaminated soil during ex-situ bioremediation. While N and P amendments are commonly used to stimulate indigenous microorganisms, the potential benefits of adding S have received less attention. The study found that historically contaminated soil with a moderate concentration of total petroleum hydrocarbons (TPH; 1270 mg/kg) did not have nutrient limitation, and incubation temperature was found to be more critical for enhancing microbial activity. However, soil spiked with an additional 5000 mg/kg of diesel showed increased activity following NP and NPS amendment. Interestingly, NPS amendment at 10 °C resulted in higher microbial activity than at 20 °C, indicating the potential for a tailored nutrient amendment approach to optimize bioremediation in cold conditions. Overall, this study suggests that incorporating S with N and P can enhance microbial activity in diesel-contaminated soil during ex-situ bioremediation. Furthermore, the study highlights the importance of considering incubation temperature in designing a nutrient amendment approach for bioremediation, especially in cold conditions. These findings can guide the design and implementation of future effective bioremediation strategies for petroleum hydrocarbon-contaminated soil.

Bioremediation of Diesel-Contaminated Soil by Fungal Solid-State Fermentation.

To address the poor removal of diesel in soil by indigenous microorganisms, we proposed a fungal solid-state fermentation (SSF) method for bioremediation. We screened Pycnoporus sanguineus 5.815, Trametes versicolor 5.996, and Trametes gibbosa 5.952 for their diesel-degrading abilities, with Trametes versicolor 5.996 showing the most promise. The fungal inoculum was obtained through SSF using wood chips and bran. Trametes versicolor 5.996 was applied to two treatments: natural attenuation (NA, diesel-contaminated soil) and bioremediation (BR, 10% SSF added to diesel-contaminated soil). Over 20 days, NA removed 12.9% of the diesel, while BR achieved a significantly higher 38.3% degradation rate. BR also increased CO2 and CH4 emissions but reduced N2O emissions. High-throughput sequencing indicated SSF significantly enriched known diesel-degrading microorganisms like Ascomycota (83.82%), Proteobacteria (46.10%), Actinobacteria (27.88%), Firmicutes (10.35%), and Bacteroidota (4.66%). This study provides theoretical support for the application of fungal remediation technology for diesel and improves understanding of microbiologically mediated diesel degradation and soil greenhouse gas emissions.

Dose–effect of nitrogen regulation on the bioremediation of diesel contaminated soil

Nitrogen regulation is an effective method to enhance the bioremediation of hydrocarbon contamination. In this study, various dosages of two types of nitrogen sources were spiked to the diesel contaminated soil in a 60-day microcosmic experiment. The results showed that the total petroleum hydrocarbon (TPH) degradation rate improved from control test of 32.03% to the highest of 44.74% with nitrogen spiking. Peptone and KNO3 significantly improved the bioremediation of diesel-contaminated soil, peptone was more effective than KNO3 at low dosage. The soil C:N ratio of 20:1 (T1 treatment with the addition of peptone) was the optimal treatment. The effect of two nitrogen on soil pH was reverse, high dose of peptone addition significantly increased soil pH, but KNO3 addition significantly decreased soil pH. The soil bacteria diversity decreased significantly in the high dose Peptone treated soil, while the changes of bacteria diversity of KNO3 treated soil was just opposite. Furthermore, nitrogen regulation significantly changed the structure of soil bacterial community, Rubrobacter, Solirubrobacter and Gaiella, which belonging to Actinomycetota, were identified as the three common genus with hydrocarbon degrading ability in different nitrogen amended soil. Peptone and KNO3 had different mechanisms on the bioremediation of diesel contaminated soil. The properties of these two nitrogen sources provides us with more options for the bioremediation of hydrocarbon contaminated acid or alkaline soil.

Study on Amendment of Rapeseed Meal, Soybean Meal, and NPK Fertilizer as Biostimulants in Bioremediation of Diesel-Contaminated Soil by Autochthonous Microorganisms

ABSTRACT The adverse impact of total petroleum hydrocarbons (TPH) can be mitigated through bioremediation. However, the efficiency of bioremediation is often compromised due to its slow speed. Therefore, this study aimed to evaluate the promoting effect of organic and inorganic biostimulants on the bioremediation rate of autochthonous microorganisms. The study examined the impact of rapeseed meal (biostimulation-BS1), soybean meal (BS2), and NPK fertilizer (BS3), as biostimulants on pH, bacterial and fungal count, enzymatic activities, and also TPH values of diesel-contaminated soil. The results revealed that amending the soil with rapeseed meal, soybean meal, and NPK fertilizer resulted in a significant increase in dehydrogenase and catalase activities, with 9.96, 7.7, and 6.75-fold and 2.52, 2.4, and 2.52-fold enhancement, respectively, compared to natural attenuation (NA-as control) which contains diesel-contaminated soil without any organic or inorganic amendments. Moreover, the pH value of the BS1 (6.4) and BS2 (6.77) groups was almost neutral. The growth of heterotrophic and hydrocarbon-utilizing bacteria and fungi was significantly improved with organic matter amendment (P < .05). The TPH removal efficiencies in natural attenuation, BS1, BS2, BS3, and rapeseed meal+ soybean meal+ NPK fertilizer (BS4) groups were 49.22%, 71.65%, 90.55%, 65.77%, and 55.25%, respectively. Molecular identification revealed that three hydrocarbon-utilizing bacteria belonged to various genera, including Nocardiopsis, Streptomyces, and Mammaliicoccus. Overall, this study suggests that amending organic compounds to contaminated soil is an effective, cost-effective, and eco-friendly strategy to improve the bioremediation rate of autochthonous microorganisms.

Dynamics of Functional Genes and Bacterial Community during Bioremediation of Diesel-Contaminated Soil Amended with Compost.

Compost is widely used as an organic additive to improve the bioremediation of dieselcontaminated soil. In this study, the effects of compost amendment on the remediation performance, functional genes, and bacterial community are evaluated during the bioremediation of diesel-contaminated soils with various ratios of compost (0-20%, w/w). The study reveals that the diesel removal efficiency, soil enzyme (dehydrogenase and urease) activity, soil CH4 oxidation potential, and soil N2O reduction potential have a positive correlation with the compost amendment (p < 0.05). The ratios of denitrifying genes (nosZI, cnorB and qnorB) to 16S rRNA genes each show a positive correlation with compost amendment, whereas the ratio of the CH4-oxidizing gene (pmoA) to the 16S rRNA genes shows a negative correlation. Interestingly, the genera Acidibacter, Blastochloris, Erythrobacter, Hyphomicrobium, Marinobacter, Parvibaculum, Pseudoxanthomonas, and Terrimonas are strongly associated with diesel degradation, and have a strong positive correlation with soil CH4 oxidation potential. Meanwhile, the genera Atopostipes, Bacillus, Halomonas, Oblitimonas, Pusillimonas, Truepera, and Wenahouziangella are found to be strongly associated with soil N2O reduction potential. These results provide useful data for developing technologies that improve diesel removal efficiency while minimizing greenhouse gas emissions in the bioremediation process of diesel-contaminated soil.

Dynamics of Functional Genes and Bacterial Community during Bioremediation of Diesel-Contaminated Soil Amended with Compost.

Compost is widely used as an organic additive to improve the bioremediation of diesel-contaminated soil. In this study, the effects of compost amendment on the remediation performance, functional genes, and bacterial community are evaluated during the bioremediation of diesel-contaminated soils with various ratios of compost (0-20%, w/w). The study reveals that the diesel removal efficiency, soil enzyme (dehydrogenase and urease) activity, soil CH4 oxidation potential, and soil N2O reduction potential have a positive correlation with the compost amendment (p < 0.05). The ratios of denitrifying genes (nosZI, cnorB and qnorB) to 16S rRNA genes each show a positive correlation with compost amendment, whereas the ratio of the CH4-oxidizing gene (pmoA) to the 16S rRNA genes shows a negative correlation. Interestingly, the genera Acidibacter, Blastochloris, Erythrobacter, Hyphomicrobium, Marinobacter, Parvibaculum, Pseudoxanthomonas, and Terrimonas are strongly associated with diesel degradation, and have a strong positive correlation with soil CH4 oxidation potential. Meanwhile, the genera Atopostipes, Bacillus, Halomonas, Oblitimonas, Pusillimonas, Truepera, and Wenahouziangella are found to be strongly associated with soil N2O reduction potential. These results provide useful data for developing technologies that improve diesel removal efficiency while minimizing greenhouse gas emissions in the bioremediation process of diesel-contaminated soil.

Development of a bacterial consortium comprising oil-degraders and diazotrophic bacteria for elimination of exogenous nitrogen requirement in bioremediation of diesel-contaminated soil.

The purpose of this study was to develop an effective bacterial consortium and determine their ability to overcome nitrogen limitation for the enhanced remediation of diesel-contaminated soils. Towards this, various bacterial consortia were constructed using oil-degrading and nitrogen-fixing microbes. The diesel removal efficiency of various developed consortia was evaluated by delivering the bacterial consortia to the diesel-contaminated soils. The consortium Acinetobacter sp. K-6 + Rhodococcus sp. Y2-2 + NH4NO3 resulted in the highest removal (85.3%) of diesel from the contaminated soil. The consortium containing two different oil-degrading microbes (K-6 + Y2-2) and one nitrogen-fixing microbe Azotobactervinelandii KCTC 2426 removed 83.1% of the diesel from the soil after 40days of treatment. The total nitrogen content analysis revealed higher amounts of nitrogen in soil treated with the nitrogen-fixing microbe when compared with that of the soil supplemented with exogenous inorganic nitrogen. The findings in this present study reveal that the consortium containing the nitrogen-fixing microbe degraded similar amounts of diesel to that degraded by the consortium supplemented with exogenous inorganic nitrogen. This suggests that the developed consortium K-6 + Y2-2 + KCTC 2426 compensated for the nitrogen limitation and eliminated the need for exogenous nitrogen in bioremediation of diesel-contaminated soils.

Bioremediation of Diesel-contaminated Soil by Composting with Locally Generated Bulking Agents

ABSTRACTHerein, we conducted a study toward understanding the impact of composting of the diesel-contaminated soil with some locally available bulking agents (rice husks (RHs), sawdust (SD), and wood chips (WCs)). In order to ascertain the effectiveness of petroleum degradation by the process assayed, we compared the protocols with monitored natural attenuation (MNA). The overall degradation pattern was modeled with non-linear regression by comparing the experimental data with first and second-order kinetic equations. At the end of the six-week study, the amount of total petroleum hydrocarbon removed from contaminated soil was 98.26 ± 1.33% (amendment with SD + RHs + WCs), 96.89 ± 1.20 (RHs amendment), 96.55 ± 1.29% (amendment with SD), 90.01 ± 0.22% (WCs amendment), and 85.02 ± 0.21% (MNA). The degradation of TPH trends followed a second-order kinetic model for all the four compost treatments while the MNA was found to follow a first-order (slower) degradation pattern. In general, the results of the parameter estimate showed that amendment with mixture of the three bulking agents was 1.08 (8%) slower (k2 = (1.289 ± 0.16) × 10−5 (g mg−1 d−1), r2 = 0.991) than SD amendment alone (k2 = (1.392 ± 0.14) × 10−5 (g mg−1 d−1), r2 = 0.995). However, the mixture of the bulking agents was found to be 1.67, 1.41, and 2.4 times faster than amendments with WCs, rice, and MNA, respectively. The phytotoxicity test revealed that all the compost treatments except WCs resulted in germination index of ≥80% after six weeks of bioremediation tests. The outcome of the current investigation confirms the effectiveness of bulking agents (especially when combined) in the supply of nutrients for the bioremediation of diesel-impacted soil.

Optimisation of Diesel Polluted Soil Using Response Surface Methodology

This research is based on the investigation of the bioremediation of diesel polluted soil using biostimulation strategy. The study was carried out on a diesel contaminated soil and concentrations: Tween 80 (5-15ml), Poultry droppings (20-60g), Hydrogen Peroxide (0.5-1.5ml) were added and incubated for 28 days of remediation period. Response Surface Methodology with Box-Behnken Design (BBD) was used with three factors and three levels of Tween 80, Poultry droppings and Hydrogen Peroxide as independent variables while diesel oil (Total Petroleum Hydrocarbon) removal was the dependent variable (response). The result showed disparities in the diesel oil biodegradation pattern with respect to Tween 80, Poultry droppings and Hydrogen Peroxide. The statistical analysis, via ANOVA showed coefficient of determination R2 to be 99.89% and P < 0.05. The predicted optimum parameter of Tween 80: 10.10ml, Poultry droppings: 41.46g and Hydrogen Peroxide: 1.10ml were gotten while 56.565% was gotten as the optimal diesel oil removal. At this optimum condition, the observed diesel oil removal was found to be 56.568%. It can be concluded that bioremediation of diesel-contaminated soil resulted in petroleum hydrocarbon degradation.

Effects of soil organic matter and bacterial community shift on bioremediation of diesel-contaminated soil

Bioremediation of diesel-contaminated soils were applied to investigating effects of soil organic matter (SOM) and bacterial community shift. Soil samples were artificially contaminated with diesel oil, ranging from 4000 to 12000 mg/kg soil, remediated with laboratory-scale landfarming batch applications. The SOM levels in our experiment were 2.3% (presented as SOM15), 8.9% (SOM092), and 11.8% (SOM125). Based on each of the SOM levels, bioremediation approaches of bioaugmentation (BA015, BA092, and BA125) and using indigenous microorganisms as control groups (CT015, CT092, and CT125) were tested. After about 300-day operation, total petroleum hydrocarbon (TPH) degradation efficiency became 73%, 63%, and 59% in SOM015, SOM092, and SOM125, respectively. Their 1st order degradation rates also reduced with the increase of SOM. We preliminarily concluded that SOM affected the TPH degradation efficiency and 1st degradation rates. With a logarithm transformation, the degradation pattern of SOM092 and SOM125 found to resemble each other. No apparent improvement was found from the BA batches. Our Intergenic spacer (ITS) microarray result indicated the existence of diesel-degrading bacteria in the indigenous communities. Nonmetric multidimensional scaling (MDS) based on terminal restriction fragment length polymorphism (T-RFLP) data indicated that 1) CT community became similar to BA community, once the 1st degradation stage started, impling an activation of the indigenous bacteria; 2) the degradation stage affected the community dynamics more than the SOM or the remediation approaches could do, and 3) both BA092 and BA125 located in the same cluster on the MDS plot all the time, revealing the similar communities. The similar communities might cause the comparable degradation patterns in SOM092 and SOM125. The bacteria community shift found useful in explaining the TPH degradation performance.

Effects of soil organic matter and ageing on remediation of diesel-contaminated soil

Bioremediation of diesel-contaminated soil was investigated for the effects of soil organic matter (SOM) and ageing time in two sets of experiments (Batch I and II, respectively). This study examined degradation efficiency in soil artificially contaminated with diesel oil (maximum total petroleum hydrocarbons (TPH) concentration of 9000 mg/kg soil). Batch I data showed that the values of the first-order degradation rate, k, were relatively high in the low-SOM soil batches. The quantity of SOM negatively correlated with the TPH degradation rates and with the total TPH degradation efficiency (%). Introduction of rhamnolipid to the soil proved to be a useful solution to resolve the problem of the residual TPH in the soil with high SOM. In Batch II, the k values decreased with the length of ageing time: 0.0245, 0.0128 and 0.0090 1/d in samples ST0 (freshly contaminated), ST38 (aged for 38 days) and ST101 (aged for 101 days), respectively. The TPH degradation efficiency (%) also decreased along with the ageing time. The research also applied molecular technology to analyse the bacterial community dynamics during the bioremediation course. Multivariate statistics based on terminal-restriction fragment length data indicated: 1) the soils with different SOM resulted in separate bacterial community structures, 2) ageing time created a variety of bacterial communities, 3) the bacterial community dynamics was associated with the hydrocarbon consumption. The SOM content in soils affected the TPH degradation rate and efficiency and the bacterial community structures. Aged soil is more difficult to remediate than freshly contaminated soil, and the resulting bacterial community was less dynamic and showed a lack of succession.

Bioremediation of diesel-contaminated soil using Bacillus sp. (strain TMY-2) in soil by uniform and non- uniform electro kinetic technology field

Selected biomakers, Cholinesterase (ChE) and phagocytic activities have been investigated with the exposed green mussel Perna viridis in Indonesian coastal waters. An operative effect-based monitoring on two polluted sites and one reference area were investigated for aquaculture enterprises and human health aspects. Between two heavily polluted sites, green mussels from Cilincing indicated a lower level of the ChE activity than those from Kamal Muara. The phagocytic activity of green mussels from the polluted sites demonstrated significant higher activity than that of green mussels from the pristine site, Pangkep. However, there were no significant differences of phagocytic activities between the polluted sites. This might indicate that the existing pollutants in Jakarta Bay were more neurotoxic rather than immonotoxic substances. The results showed clearly that both selected biomarkers were potential valuable tools for effect-based monitoring and pollution impacts in coastal zones of Indonesia. Key words: Green mussel, biomarkers, coastal zone management, Indonesia.

Effects of biostimulation and bioaugmentation on diesel removal and bacterial community

The evolution of the bacterial community during the bioremediation of diesel-contaminated soil using laboratory scale bioreactors was investigated for 120 days, evaluating the effect of adding individually or together, a mature compost, a bacterial consortium and the biosurfactant (β-cyclodextrin). The dynamics of microbial community was assessed using both a culture-dependent method and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA gene fragments. Results showed that the addition of compost plus a bacterial consortium caused a progressive increase in both heterotrophic cultivable aerobic bacteria and presumptive Pseudomonas. During the initial stage of the process, biostimulation and bioaugmentation increased species diversity (evaluated by DGGE analysis) and increased biomass-C content. After a transient drop caused by the xenobiotic contaminant, the bacterial community diversity and biomass-C content were restored at the end of the process. The density and activity of the microflora were similar in microcosms with or without β-cyclodextrin, but under the conditions tested, a reduction in total petroleum hydrocarbon (THP) removal was observed in the microcosms containing β-cyclodextrin. The combined use of mature compost and of a selected microbial consortium is a useful strategy for improving TPH removal, achieving a high TPH degradation (96%) at the end of the bioremediation process (120 days).

The Effect of Temperature and Aeration Rate on Bioremediation of Diesel-contaminated Soil in Solid-phase Bench-scale Bioreactors

Bioremediation of hydrocarbon (HC) contaminated soils is most effective in aerobic conditions. Despite the fact that mass transfer of oxygen is an important process parameter, the effect of this parameter on solid-phase bioremediation has received limited attention. In this study, the combined effect of temperature and aeration on the bioremediation of low organic content coarse-grained soils, freshly contaminated with diesel, was investigated in solid-phase bench-scale bioreactors. Total HC and carbon range soil concentrations, volatilization, and microbial activity were monitored throughout the six-month experiments at two temperatures (7 and 22°C) and at two aeration rates (13 and 45 mL·s−1). Total HC removal reached between 48 and 83%. Generally, removal increased proportionally with temperature and aeration rates, and decreased proportionally with HC compounds molecular weight. Both biodegradation and volatilization played important roles in removal in all treatments. The high aeration rate enhanced microbial activity in soil. Enhancement was believed to be due to increased mass transfer of oxygen from the soil gas to the soil solution, where microbial activity occurs. However, high aeration also enhanced volatilization, especially at 22°C where 51% of HCs were lost to volatilization. High aeration rate enhanced biodegradation of compounds > nC15 without promoting their excessive volatilization.

Bioremediation of diesel-contaminated soil by heated and humidified biopile system in cold climates

Abstract Bioremediation is a proven and widely accepted technology for the remediation of soil contaminated with various mixtures of petroleum hydrocarbons (PHC) in temperate climates but its application in cold climates has received far less attention. Low ambient temperature is one of the main factors limiting microbial degradation of the organic contaminants in such locations. Heating the soil should therefore enhance bioremediation as laboratory studies have shown increased biodegradation rates in Arctic soils with increasing soil temperature. A biopile is one of the many bioremediation techniques to treat hydrocarbon-contaminated soil where the soil is piled over an air distribution system and aerated. The air distribution system can also be used to provide heat to the soil in order to optimize soil temperature when conditions are limiting. However, heating the soil by forced air may cause excessive drying of the soil which may inhibit microbial activity and promote volatilization of the contaminants rather than their biodegradation. During treatment of hydrocarbon contaminated soils in a biopile system, biodegradation is preferred over volatilization and should be optimized. Few field-scale studies have tested the use of heated biopile systems in cold climates. This paper examines the effect of humidifying the air for the treatment of PHC-contaminated soil by an aerated/heated biopile system. Three biopiles were constructed with soil freshly contaminated with diesel fuel (initial total petroleum hydrocarbon concentration, [TPH], ~ 11,000 mg/kg dry weight) and operated for 10 months in Kingston, ON, Canada. One biopile was heated with an aerating/heating system previously tested in the Arctic. A second biopile was also aerated and heated but received water by humidifying the air prior to entering the soil pile. A third biopile was passively aerated by pipes protruding from the soil pile. TPH, available nutrients content, and pH were monitored by periodic collection and analysis of soil samples. Volatilization of hydrocarbon compounds was measured by trapping them on activated charcoal. Temperature and moisture were monitored continuously with a datalogger. Hydrocarbon concentrations in soil and charcoal samples were measured by solvent extraction followed by gas chromatography flame ionization detection (GC/FID) analysis. Significant TPH reduction was observed in all systems. TPH reduction followed first-order kinetics for the first two-third of the treatment. The humidified system maintained optimal soil moisture content and produced significantly lower final TPH than the other two treatments (~ 300 mg/kg dry weight). Findings suggest that humidifying the air enhanced biodegradation and minimized volatilization. The removal of hydrocarbons of different carbon chain lengths was investigated by GC/FID analysis. Three hydrocarbon fractions were defined ( nC15) based on equivalent straight-chain alkane ranges. Results from this analysis showed that all fractions were removed during treatment, but the overall data suggest that biodegradation was dominant for the highest molecular weight fraction.

Implication of hydraulic properties of bioremediated diesel-contaminated soil

The hydraulic properties, such as hydraulic conductivity and water retention, of aged diesel-contaminated and bioremediated soils were examined and implications of the hydraulic properties for assessing bioremediation performance of soils were proposed. Bioremediation of diesel-contaminated soil was performed over 80 d using three treatments; (I) no nutrient added, column-packed soil, (II) nutrient added, column-packed soil, and (III) nutrient added, loosen soil. Diesel reduction in treatment I soil (control soil) was negligible while treatment III showed the greatest extent of diesel biodegradation. All treatments showed greatest rates of diesel biodegradation during the first 20 d, followed by a much retarded biodegradation rate in the remaining incubation period. Reduction of the degradation rate due to entrained diesel within inaccessible soil pores was hypothesized and tested by measuring the hydraulic properties of two column-packed soils (treatments I and II). The hydraulic conductivity of treatment II soil (nutrient added) was consistently above that of treatment I soil (no nutrient added) at pressure heads between 0 and 15 cm. In addition, the water retention of treatment II soil was greater at pressure heads <100 cm (equivalent to pore size of >30 μm), suggesting that biodegradative removal of hydrocarbons results in enhanced wettability of larger soil pores. However, water retention was not significantly different for control and biodegraded soils at pressure heads >100 cm, where smaller size soil pores were responsible for the water retention, indicating that diesel remained in smaller soil pores (e.g., <30 μm). Both incubation kinetics and hydraulic measurements suggest that hydrocarbons located in small pores with limited microbe accessibility may be recalcitrant to bioremediation.

06/01429 Challenge of transmutation of long-lived nuclides: Artisyuk, V. et al. Progress in Nuclear Energy, 2005, 47, (1–4), 327–338

The evolution of the bacterial community during the bioremediation of diesel-contaminated soil using laboratory scale bioreactors was investigated for 120 days, evaluating the effect of adding individually or together, a mature compost, a bacterial consortium and the biosurfactant (β-cyclodextrin). The dynamics of microbial community was assessed using both a culture-dependent method and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA gene fragments. Results showed that the addition of compost plus a bacterial consortium caused a progressive increase in both heterotrophic cultivable aerobic bacteria and presumptive Pseudomonas. During the initial stage of the process, biostimulation and bioaugmentation increased species diversity (evaluated by DGGE analysis) and increased biomass-C content. After a transient drop caused by the xenobiotic contaminant, the bacterial community diversity and biomass-C content were restored at the end of the process. The density and activity of the microflora were similar in microcosms with or without β-cyclodextrin, but under the conditions tested, a reduction in total petroleum hydrocarbon (THP) removal was observed in the microcosms containing β-cyclodextrin. The combined use of mature compost and of a selected microbial consortium is a useful strategy for improving TPH removal, achieving a high TPH degradation (96%) at the end of the bioremediation process (120 days).

Bioremediation of diesel-contaminated soil by microorganisms immobilised in polyvinyl alcohol

It is argued that bioaugmentation is best reserved for particularly recalcitrant contaminants where an autochthonous population may be missing, and that selection has produced the microbial diversity required for clean-up of less recalcitrant contaminants. However, biodegradable contaminants may persist as a result of sub-optimal environmental conditions such as temperature, pH, electron acceptor availability and biotic factors such as predation by protozoa. A role for immobilised-cell bioaugmentation may therefore still be envisaged for the bioremediation of, say, persistent fuel spills under such conditions, or in extreme environments. In this laboratory-scale study we examined the potential of immobilised hydrocarbon-degrading microorganisms for the clean up of diesel-contaminated soil. We used polyvinyl alcohol (PVA) cryogelation as an entrapment technique and microorganisms indigenous to the site. We constructed laboratory biopiles to compare immobilised bioaugmentation with liquid culture bioaugmentation and biostimulation. In terms of percentage removal of diesel after 32 days, the immobilised systems were found to be the most successful, with greatest removal in a co-immobilisation system containing PVA-entrapped microorganisms and a synthetic oil absorbent. Least success was achieved with a commercial liquid bioaugmentation agent containing surfactants and having a low pH, which also produced significant phytotoxicity. Other advantages of PVA cryogelation are discussed.

Bioremediation of diesel-contaminated soil with composting

The major objective of this research was to find the appropriate mix ratio of organic amendments for enhancing diesel oil degradation during contaminated soil composting. Sewage sludge or compost was added as an amendment for supplementing organic matter for composting of contaminated soil. The ratios of contaminated soil to organic amendments were 1:0.1, 1:0.3, 1:0.5, and 1:1 as wet weight basis. Target contaminant of this research was diesel oil, which was spiked at 10,000 mg/kg sample on a dry weight basis. The degradation of diesel oil was significantly enhanced by the addition of these organic amendments relative to straight soil. Degradation rates of total petroleum hydrocarbons (TPH) and n-alkanes were the greatest at the ratio of 1:0.5 of contaminated soil to organic amendments on wet weight basis. Preferential degradation of n-alkanes over TPH was observed regardless of the kind and the amount of organic amendments. The first order degradation constant of n-alkanes was about twice TPH degradation constant. Normal alkanes could be divided in two groups (C10–C15 versus C16–C20) based on the first order kinetic constant. Volatilization loss of TPH was only about 2% of initial TPH. Normal alkanes lost by volatilization were mainly by the compounds of C10 to C16. High correlations ( r=0.80–0.86) were found among TPH degradation rate, amount of CO 2 evolved, and dehydrogenase activity.

In-situ bioremediation of diesel-contaminated soil in Canada's Arctic territory: a case study at the Whitehorse International Airport, Yukon Territory

AbstractEffective remediation of petroleum-contaminated soils in the Arctic is becoming increasingly important as the magnitude of environmental risks becomes better defined. Unfortunately, some of the solutions implemented in southern Canada are too costly to use in the Arctic. However, effective remediation is still necessary. Consequently, traditional techniques are employed, such as excavation and landfarming, which are disruptive to the immediate soils, permafrost, and the surrounding habitat. These remedial methods, however, are becoming unacceptable to First Nations people in some Canadian Arctic communities. This paper describes preliminary results from an in-situ biodegradation study of petroleum-contaminated soils. This technique has the potential to provide an easily applied effective solution to the problem of devising a low cost and uncontroversial method of remediation. Based on bench-scale laboratory feasibility studies, it has been determined that the zone of contaminated soil at the Whitehorse Airport is suitable for in-situ bioremediation application.