Degradation Rate Of Total Petroleum Hydrocarbons Research Articles

Study on the co-catalytic performance and mechanism of MoO2 in oil-contaminated wastewater treated by Fenton system

BackgroundIn the treatment of organic wastewater, Fenton technology often produces iron sludge due to iron circulation obstruction, which inhibits the treatment efficiency and causes secondary pollution to the actual water. MethodsIn this study, MoO2 was used as a cocatalyst to promote the effective cycling of Fe2+/Fe3+ in the Fe2+/H2O2 system, thus efficiently degrading total petroleum hydrocarbons (TPHs). The superiority of MoO2 as co-catalyst was verified under different reaction conditions, and its mechanism was discussed. FindingsThe degradation rate of TPHs in the Fe2+/H2O2/MoO2 system (0.069 min−1) was about 14 times that of Fe2+/H2O2 system (0.005 min−1). Compared with the Fe2+/H2O2 system, the Fe2+/H2O2/MoO2 system not only had a wider pH adaptation range, but also could effectively remove TPHs under the interference of co-existing organic and inorganic anions. MoO2 did not change the types of reactive species in Fenton system, but it enhanced the production of reactive oxygen species (ROS) by promoting the Fe2+/Fe3+ cycling in the reaction system, and ·OH was the main reactive species of TPHs degradation.

In‐situ remediation of TPH‐polluted soil by Na2FeO4 in the Loess Plateau of China

AbstractIn recent years, the oil pollution problem on the Loess Plateau in western China is becoming increasingly serious, therefore, the use of hydroxyl radical (·OH) advanced oxidation process has increased due to its ability to efficiently degrade total petroleum hydrocarbon (TPH) in soil. However, the ability to produce ·OH of different oxidants varies widely, and the removal effect of specific pollutants has fluctuations and differences. The objective of this study is to screen the best oxidant according to the physico‐chemical properties and pollution situation of polluted soil, and to reveal the degradation mechanism of pollutants. In this study, we employed sodium ferrate (Na2FeO4) to produce ·OH for the degradation of TPHs in aged oil‐polluted soil located in the western part of the Loess Plateau in China. The results showed that the removal rates of TPH in the soil samples by hydrogen peroxide (H2O2), sodium persulfate (Na2SO4) and Na2FeO4 could reach 45.5%, 62.4%, and 65.6% respectively. The ·OH produced during the process played a major role in TPH oxidation with a contribution of more than 80%; H2O2 was intermediate substance that generated ·OH, biochar could induce the production of ·OH, the addition of biochar could activate H2O2 to promote the generation of ·OH and the removal rate is significantly increased by 19.2%. In situ remediation of polluted soil on the Loess Plateau using Na2FeO4, with a TPH degradation rate of 87.5%. The results of this study will provide a new method for the efficient degradation of TPH in loessial soil.

Predicting selected kinetic parameters of hydrocarbon interactions with alum-based water treatment residuals

Kinetic parameters of hydrocarbon interactions with alum-based water treatment residuals (WTR) in the biostimulation of crude oil-polluted soil are very important because they reveal how long the WTR bind with the hydrocarbon to control its fate and transport in the soil. In this study, we used Michaelis-Menten biokinetic model to determine two important kinetic parameters, the maximum specific rate constant (μmax) and Michaelis-Menten constant (Km), as well as total petroleum hydrocarbon (TPH) degradation rate equation in the biostimulation of crude oil-polluted Niger Delta Oxisols using WTR synthesized from local fishpond effluents. Using the completely randomized design, the experimental setup consisted of 6-duplicate reactors including the control (labelled A to F) containing mixtures of soil, crude oil, and WTR in the ratios of 4:1:0, 4:1:1, 4:1:1.5, 4:1:2, 4:1:2.5, and 4:1:3, respectively. Treatment lasted for 70 days and TPH concentration was determined by gas chromatography-mass spectrometry (GC-MS). Results showed that a rounded average of 51% TPH reduction was achieved after 70 days of treatment. The rounded average of μmax was 0.5 mg/kg-day and Km was 270 mg/kg, while the TPH degradation rate equation was deduced as r=−0.5S/(270+S) at any TPH concentration, S. With an average root-mean-square error of 4.998 mg/kg, residual prediction deviation of 18.08, and corresponding validation r2 of over 99%, the model prediction was categorized as excellent with an error of only 1%. This shows the potential of the model to predict TPH in the biostimulation of crude oil-polluted Niger Delta Oxisols with alum-based WTR.

Remediation and Optimisation of Petroleum Hydrocarbon Degradation in Contaminated Water by Persulfate Activated with Bagasse Biochar-Supported Nanoscale Zerovalent Iron

In this study, biochar (BC) was prepared from bagasse and then successfully loaded with nanoscale zerovalent iron (nZVI) to produce BC-supported nZVI, termed nZVI@BC. Satisfactory results were obtained using a nZVI@BC-activated persulfate (PS), termed nZVI@BC/PS, to remediate total petroleum hydrocarbons (TPH)-contaminated water. The effects of three influencing factors—the dosage of nZVI@BC, DnZVI@BC, the concentration of PS, CPS, and the initial pH, pHi—on TPH removal were examined through single-factor and batch tests. The results show the following. Each factor considerably influenced the performance of the prepared nZVI@BC/PS reaction system in removing TPH. The TPH degradation process conformed to a first-order kinetic model. The response surface method (RSM) was used in tandem with a Box–Behnken design to optimise the variables involved in TPH degradation. The three influencing variables (i.e., DnZVI@BC, CPS, and pHi) were set in the range of 0.4–1.0 g/L, 20–160 g/L, and 2.21–9.42, respectively, during the experiment. An optimised quadratic model used to fit the experimental data displayed a high level of significance (p < 0.0001) with a very high regression value (R2 = 0.9906; adjusted R2 = 0.9786). Analyses of regression and variance revealed that the quadratic model sufficiently explains the TPH degradation rate. An electron paramagnetic resonance (EPR) spectroscopic analysis of the nZVI@BC/PS system revealed that SO4−·, ·OH, O2−·, and 1O2 participated in the activation and degradation processes. The results of this study show that nZVI@BC-activated PS systems possess great potential for applications in TPH-contaminated wastewater treatment and environmentally sustainable development.

Coupling biostimulation and phytoremediation for the restoration of petroleum hydrocarbon-contaminated soil

Total petroleum hydrocarbons (TPH) continue to be among the most common pollutants in soil worldwide. Bioremediation and phytoremediation have become sustainable ways of dealing with TPH contamination and biostimulation-assisted phytoremediation is considered as a potential approach for the treatment of pollutants. In this study, the response surface was used to optimize the single-factor biological stimulation experiment of moisture content, leavening agent content and compound fertilizer content and got the best experimental plan of biological stimulation. It was found that TPH degradation rate was 28.6% by biostimulation after 70 days. Further, from 20 kinds of plant seeds, 5 kinds of suitable or growth and high germination rate were selected for petroleum hydrocarbon degradation experiment. In the phytoremediation, peanut was selected as the best plant species by measuring the TPH degradation rate, bacteria count, growth of test plants, germination rate and amount of catalase in the soil and it could achieved 31.1% degradation rate of petroleum hydrocarbons after 70 days. Finally, the artificial biostimulation and phytoremediation combined degradation experiment of petroleum hydrocarbons-contaminated soil was designed and it achieved 38.9% TPH degradation rate after 70 days.

Assessing the degradation potential of light petroleum hydrocarbons using bacterial activity (Pseudomonas aeruginosa) and root exudate of Conocarpus (Conocarpus erectus)

Petroleum hydrocarbons are one of the most common environmental pollutants, leading to serious environmental problems; and phytoremediation is an environmentally friendly way to remove petroleum pollutants from the soil. This research was designed based on the relatively high salinity of Ahwaz soil, the resistance of Conocarpus to soil salinity, and the presence of Pseudomonas bacteria in most environments. The aim of this study was to assess the effect of Conocarpus erectus and Pseudomonas aeruginosa on the removal efficiency of total petroleum hydrocarbons (TPHs) from contaminated soils with Bangestan crude oil in the phytoremediation process during 275 days under non-laboratory condition. After pedological studies and the selection of evaporation pond in crude oil desalination plant with suitable conditions for phytoremediation, this study was conducted in a factorial experiment with two factors based on completely randomized design with three replications. The factors used in this experiment include the treatment types (plant, bacteria, plant–bacteria cultivated in the soil, and soil with no plant and bacteria (control)) and the concentration of contaminant (Bangestan crude oil) with 5 levels (0, 0.5, 1, 2.5 and 5 wt%). TPHs were measured in soil samples collected from the rhizosphere of Conocarpus using gas chromatography with a flame ionization detector (GC-FID). The degradation rate of TPHs in soil with Conocarpus, Pseudomonas, and Conocarpus-Pseudomonas was 38.1%, 35.95%, and 70.54%, respectively. The results of the experimental factors showed that although plant and bacteria individually had a positive effect on the degradation of TPHs, the combination of bacteria and plants led to a more positive and significant effect on the degradation of TPHs ( P < 0 . 05 ).

Potentiality of Azolla pinnata R. Br. for Phytoremediation of Polluted Freshwater with Crude Petroleum Oil

The pollution of freshwater resources with crude petroleum oil is a major environmental issue in oil-producing countries. As a result, the remediation of polluted aquatic ecosystems using eco-friendly and cost-effective technology is receiving increased global attention. In this study, the ability of Azolla pinnata R. Br. to remediate petroleum-polluted freshwater was assessed. The remediation potentiality was determined by evaluating the total petroleum hydrocarbon degradation percentage (TPH%) and changes in the molecular type composition of saturated and aromatic hydrocarbon fractions. TPH% was estimated gravimetrically, and changes in the molecular type composition of saturated and aromatic fractions were measured using gas chromatography and high-performance liquid chromatography, respectively. The results reveal that A. pinnata has the potential to phytoremediate freshwater polluted with low levels (up to 0.5 g/L) of petroleum hydrocarbons (PHs). After seven days of phytoremediation, the degradation rate of total PHs was 92% in the planted treatment compared with 38% in the unplanted positive control. The highest breakdown of PHs for the normal paraffinic saturated hydrocarbon fraction occurred in the presence of A. pinnata combined with Anabena azollaea (A-A), which showed a moderate degradation capacity toward total aromatic hydrocarbons (TAHs) and total polycyclic aromatic hydrocarbons (PAHs). The results indicate that A. pinnata effectively removed C18, a saturated PH, and acenaphthene (Ace), an aromatic PH. Therefore, this study suggests that A. pinnata is a useful tool for the remediation of freshwaters contaminated with low pollution levels of crude oil.

Metagenomics analysis identifies nitrogen metabolic pathway in bioremediation of diesel contaminated soil

Nitrogen amendment is known to effectively enhance the bioremediation of hydrocarbon-contaminated soil, but the nitrogen metabolism in this process is not well understood. To unravel the nitrogen metabolic pathway(s) of diesel contaminated soil, six types of nitrogen sources were added to the diesel contaminated soil. Changes in microbial community and soil enzyme genes were investigated by metagenomics analysis and chemical analysis through a 30-day incubation study. The results showed that ammonium based nitrogen sources significantly accelerated the degradation of total petroleum hydrocarbon (TPH) (79–81%) compared to the control treatment (38%) and other non-ammonium based nitrogen amendments (43–57%). Different types of nitrogen sources could dramatically change the microbial community structure and soil enzyme gene abundance. Proteobacteria and Actinobacteria were identified as the two dominant phyla in the remediation of diesel contaminated soil. Metagenomics analysis revealed that the preferred metabolic pathway of nitrogen was from ammonium to glutamate via glutamine, and the enzymes governing this transformation were glutamine synthetase and glutamate synthetase; while in nitrate based amendment, the conversion from nitrite to ammonium was restrained by the low abundance of nitrite reductase enzyme and therefore retarded the TPH degradation rate. It is concluded that during the process of nitrogen enhanced bioremediation, the most efficient nitrogen cycling direction was from ammonium to glutamine, then to glutamate, and finally joined with carbon metabolism after transforming to 2-oxoglutarate.

Laboratory-scale bioremediation potential of single and consortia fungal isolates from two natural hydrocarbon seepages in Trinidad, West Indies

A study was conducted to isolate and evaluate the hydrocarbon-degrading potential of indigenous fungi in consortia from natural petroleum seepages in Trinidad. Sixty-seven isolates were obtained from two seepages using medium containing four single hydrocarbon fractions: diesel, naphthalene, pyrene, and asphaltene. The majority of the isolates belonged to the genera Aspergillus (52%) and Fusarium (20%), while fewer belonged to the genera Penicillium and Curvularia, and the order Mucorales (2–14%). The isolates were initially screened for degradation of crude oil in BSM broth before the top 16 (4 per hydrocarbon) were evaluated in soil spiked with single hydrocarbons over 28 days. Three consortia comprising the best performing isolates from each hydrocarbon were then evaluated for their bioremediation potential using soil spiked with crude oil and the four hydrocarbons. Consortium 1, comprising of the top degraders (Aspergillus terreus-SRF-15 (diesel), Fusarium proliferatum-SRF-50 (naphthalene), Fusarium sp-SRF-58, (pyrene) and Aspergillus sp-SRF-67 (asphaltene)), was the most effective with a total petroleum hydrocarbon degradation rate of 92% as compared to the other consortia (64–76%) and the single isolates (10–65%) over a 28-day period. The results of this study show great potential for using indigenous fungi to develop consortia for bioremediation in tropical environments.

Biological Degradation and Transformation Characteristics of Total Petroleum Hydrocarbons by Oil Degradation Bacteria Adsorbed on Modified Straw.

We report a simple and “green” method for the fabrication of polymer-modified straw-supported oil degradation bacteria (PMS-ODB) for biological degradation of total petroleum hydrocarbons (TPHs) in water. The modification of straw was achieved by in situ copolymerization of styrene and butyl methacrylate using methylene-bis-acrylamide as a cross-linker in an aqueous solution containing straw powders. Compared with the control group (ODB loaded on untreated straw), the results obtained from the experimental group show that the polymer-modified straw is beneficial to the growth of microorganisms. As a result, the degradation rate of TPHs reaches 90.12%, which is 50.54 and 7.08% higher than that of the blank group (ODB only) and the control group, respectively. A study on the transformation characteristics of PMS-ODB shows that the degradation rate of alkanes with low, medium, and high carbon number is higher than 90%. w(∑C21–)/w(∑C22+) (the mass ratio of normal alkanes of high carbon/low carbon), w(pr)/w(ph) (the ratio of pristane/phytane), and OEP (the mass ratio of normal alkanes of odd carbon/even carbon) for TPHs in the experimental group were measured to be 0.6186, 0.7248, and 1.4356, respectively, all of which are the largest value among the blank group, control group, and experimental group. These findings indicate that compared with the control group, the modification of straw could enhance the comprehensive biological degradation performance for TPHs, even those highly stable organics, such as carbon n-alkanes and isoprenoid hydrocarbon, which may open a new possibility for degradation of oils or toxic organics in an enhanced biological manner.

Growth tolerance and remediation potential of six plants in oil-polluted soil

The aim of this study was to screen plant species for remediation of oil-polluted soil in a semi-arid loess area. Pot experiments were conducted to test six indigenous plant species: ryegrass (Lolium perenne), tall fescue (Festuca ovina), wheatgrass (Agropyron cristatum), alfalfa (Medicago sativa), erect milkvetch (Astragalus adsurgens), and caragana (Caragana korshinskii). Loessial soil was spiked with crude oil at five pollution levels (0, 0.5, 1, 2, and 4%, w/w). We analyzed plant growth parameters at different stages, soil oxidoreductase activities, and oil degradation rate under different treatments. Soil pollution by oil negatively affected the germination rate, plant height, and biomass of all six species while inhibiting soil dehydrogenase and catalase activities. These inhibitory effects increased with increasing oil pollution level, with 2% and 1% being the critical levels at which plant growth and soil oxidoreductase activities were significantly inhibited, respectively. Both oxidoreductase activities in the rhizosphere soil were significantly higher than those in the bulk soil, which led to a considerable increase in the degradation rate of total petroleum hydrocarbons (TPHs) in the rhizosphere. The plants showed varying remediation effects in the oil-polluted soil. Erect milkvetch and caragana showed potential for remediation of soil below the 0.5% pollution level, alfalfa for soil below the 1% pollution level, and ryegrass, tall fescue, and wheatgrass for soil below the 4% pollution level. The oil pollution level was negatively correlated with plant height, biomass, oxidoreductase activities, and TPH degradation rate for the six plants (p < 0.01), whereas plant biomass was positively correlated with plant height and TPH degradation rate (p < 0.01). Dehydrogenase activity was significantly positively correlated with catalase activity (p < 0.01), while both of them were positively correlated with TPH degradation rate (p < 0.05 and p < 0.01, respectively). In conclusion, the six indigenous plants exhibited different tolerances to oil pollution, among which ryegrass, tall fescue, and wheatgrass had the greatest potential for remediation of oil-polluted soil in the loess area.

Effect of rhamnolipids on enhanced anaerobic degradation of petroleum hydrocarbons in nitrate and sulfate sediments

Anaerobic degradation of petroleum hydrocarbons (PH) is an important process in contaminated environment. The application of rhamnolipids in anaerobic degradation of PH was not extensively studied and inconclusive. This study explored the combined effect of rhamnolipids and electron acceptors on the anaerobic degradation process of total petroleum hydrocarbons (TPH) in sediment from an oil field. The results indicated that rhamnolipids decreased the surface tension of the medium and increased the desorption of TPH from the sediment. After 10-wk culture, the maximum degradation rate of TPH in nitrate and sulfate condition was found to be 32.2% and 24.0%, respectively, with rhamnolipids concentration of 150 mg/L. The addition of 45 and 150 mg/L rhamnolipids increased the degradation rate of TPH but the promotion effect was weakened in the treatment with 450 mg/L rhamnolipids. The copy number of two degradation genes (1-methylalkyl) succinate synthase gene (masD) and 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase gene (bamA) increased with incubation time and showed higher copy numbers in treatments with 45 and 150 mg/L rhamnolipids. In the first week, with the increase of rhamnolipids concentration, the copy number of 16S rDNA increased rapidly and the concentration of electron receptors decreased correspondingly. Moreover, no nitrate was detected in treatments of nitrate with 450 mg/L rhamnolipids after the first week. Microbial community structure analysis result showed that Thiobacillus was the dominant bacteria in all treatments with nitrate as electron acceptor and its proportion gradually decreased with the increase of rhamnolipids concentration. The addition of rhamnolipids changed the subdominant bacteria in the treatments with nitrate as electron acceptor. Methanothrix was the dominant archaea in all treatments with rhamnolipids content of lower than 45 mg/L. When the rhamnolipids concentration increased, the dominant archaea changed to Methanogenium or Methanobacterium. In conclusion, suitable concentrations of rhamnolipids could promote the anaerobic degradation of PH in the sediment.

Response surface optimization and effects of agricultural wastes on total petroleum hydrocarbon degradation

This study was carried out to investigate the effects of Goat manure (GM) and Palm oil mill effluent (POME) on total petroleum hydrocarbons (TPHs) degradation. Microbial respiration rates (CO2 evolution) were investigated. TPHs degradation rate constants were estimated using the first-order kinetics model. Scanning electron microscope (SEM) and infrared spectroscopy (FT-IR) were used to investigate the surface morphologies and functional groups in GM and POME. The CO2 evolution rates in TPH contaminated soil treated with GM (TPHCS-GM), TPH contaminated soil treated with POME (TPHCS-POME), and the untreated TPH contaminated soil (UTPHCS) were 497 mg/g, 440 mg/g, and 296 mg/g, respectively. TPHCS-GM showed higher TPH degradation rate with corresponding lower half-lives. Results from the physiochemical characterization indicated that GM performed better in restoring the scarce nutrient in the TPH contaminated soil. 58% and 39% of TPH were degraded at pH 8 and 4 in TPHCS-GM and TPHCS-POME, respectively. The response surface optimization process indicated the accuracy of the quadratic model (R2 value of 0.9891) in predicting TPH degradation (76.59%) with optimum independence variables of initial TPH concentration (300 g/L) and pH (6). The results obtained from this work showed the positive prospects of GM and POME as organic nutrients in TPH contaminated soil.

Effective treatment of oily scum via catalytic wet persulfate oxidation process activated by Fe2+

Oily scum, a hazardous by-product of petroleum industry, need to be deposed urgently to reduce environmental risks. This paper introduces catalytic wet persulfate oxidation (CWPO) process in the treatment of oily scum to realize risk relief. Under the activation of heat and Fe2+, persulfate (PS) was decomposed into sulfate radicals and hydroxyl radicals, which played a major role on the degradation of petroleum hydrocarbons. The effects of wet air oxidation (WAO) and CWPO process on the degradation of oily scum were compared. In CWPO process, the total petroleum hydrocarbons (TPHs) content of oily scum was decreased from 92.63% to 16.75%, which was still up to 70.19% in WAO process. The degradation rate of TPHs in CWPO process was about 3.38 times higher than that in WAO process. The great performance of CWPO process was also confirmed by elemental analysis, which indicated that the C and H contents of oily scum were reduced significantly by CWPO process. These results indicated that CWPO process has high potential on the degradation of oily scum for environmental protection.

Bioremediation of diesel and lubricant oil-contaminated soils using enhanced landfarming system

Lubricant and diesel oil-polluted sites are difficult to remediate because they have less volatile and biodegradable characteristics. The goal of this research was to evaluate the potential of applying an enhanced landfarming to bioremediate soils polluted by lubricant and diesel. Microcosm study was performed to evaluate the optimal treatment conditions with the addition of different additives (nutrients, addition of activated sludge from oil-refining wastewater facility, compost, TPH-degrading bacteria, and fern chips) to enhance total petroleum hydrocarbon (TPH) removal. To simulate the aerobic landfarming biosystem, air in the microcosm headspace was replaced once a week. Results demonstrate that the additives of activated sludge and compost could result in the increase in soil microbial populations and raise TPH degradation efficiency (up to 83% of TPH removal with 175 days of incubation) with initial (TPH = 4100 mg/kg). The first-order TPH degradation rate reached 0.01 1/d in microcosms with additive of activated sludge (mass ratio of soil to inocula = 50:1). The soil microbial communities were determined by nucleotide sequence analyses and 16S rRNA-based denatured gradient gel electrophoresis. Thirty-four specific TPH-degrading bacteria were detected in microcosm soils. Chromatograph analyses demonstrate that resolved peaks were more biodegradable than unresolved complex mixture. Results indicate that more aggressive remedial measures are required to enhance the TPH biodegradation, which included the increase of (1) microbial population or TPH-degrading bacteria, (2) biodegradable carbon sources, (3) nutrient content, and (4) soil permeability.

유류오염 토양 내 석유계 탄화수소 화합물의 분해에 대한 퇴비의 시용 효과

BACKGROUND: Petroleum-contaminated soil from leaking above- and underground storage tanks and spillage during transport of petroleum products is widespread environmental problem in recent years. Application of compost may be the most promising, cost-effective, and eco-friendly technology for soil bioremediation because of its advantages over physical and chemical technology. The objective of this study was to evaluate effect of compost application on degradation of total petroleum hydrocarbon (TPH) in petroleum hydrocarbon-contaminated soil. METHOD AND RESULTS: An arable soil was artificially contaminated by diesel, and compost was applied at the different rate of 0, 10, 30, and 50 Mg/ha. Concentration of TPH in the soil decreased as application rate of compost increased. Degradation efficiency was highest at compost 30 Mg/ha; however, it slightly decreased with compost 50 Mg/ha. Kinetic modeling was performed to estimate the rates of chemical reaction. The correlation coefficient (R2) values for the linear plots using the second-order model were higher than those using the first-oder model. Compost 30 and 50 Mg/ha had the fastest TPH degradation rate in the second-order model. Change of microbial population in soil with compost application was similar to that of TPH. Microbial population in the soil increased as application rate of compost increased. Increasing microbial population in the contaminated soil corresponded to decreased in TPH concentration. CONCLUSION: Conclusively, compost application for soil bioremediation could be an effective response to petroleum hydrocarbon-contaminated soil. The increase in microbial population with compost suggested that compost application at an optimum rate might enhance degradation of TPH in soil.

Enhanced biodegradation of aged petroleum hydrocarbons in soils by glucose addition in microbial fuel cells

AbstractBACKGROUNDBioelectrochemical remediation of soils contaminated by petroleum hydrocarbons has received increasing attention as an effective approach to remove pollution with simultaneous electricity generation.RESULTSHere, glucose was added as a co‐substrate in this system. The charge output of soil microbial fuel cells (MFCs) was enhanced by 262%, and the total petroleum hydrocarbon degradation rate increased by 200%. According to the increased dehydrogenase and polyphenol oxidase activities, the exogenetic glucose substantially activated hydrocarbon degradation bacteria (such as Alcanivorax). The Shannon–Wiener Index and richness of soil microbial community decreased after glucose addition, indicating that a selective enrichment of specific communities was imposed by glucose. Correlation analysis showed the biodiversity in soil far from the cathode was mainly determined by the concentration of petroleum hydrocarbons, while that in soil close to the cathode was dominated by the current.CONCLUSIONThis study demonstrated that an exogenetic carbon source enhanced the bioelectrochemically assisted degradation of aged petroleum hydrocarbons in saline soils, providing an effective approach to remove contaminations from soil in barren areas or extreme environments. © 2015 Society of Chemical Industry

Rapid remediation of soil heavily contaminated with hydrocarbons: a comparison of different approaches

To improve our understanding of the dissipation kinetics of total petroleum hydrocarbons (TPH), we tested two bioremediation strategies in soil heavily contaminated with hydrocarbons. In one strategy, different fertilizers and composted winery products were used to stimulate a local microbial community capable of dissipating petroleum hydrocarbons. In the second approach, polluted soil was used for the enrichment and isolation of potential hydrocarbon-degrading bacteria that were subsequently used for implementing a bioaugmentation strategy. The efficacy of both strategies was evaluated using the Hockey-Stick and first-order kinetics models. Two Pseudomonas isolates designated as el20 and el15 were able to readily degrade TPH and n-alkanes both in vitro and in a microcosm study. Phylogenetic analysis based on 16sRNA gene sequencing revealed that both strains showed a high similarity with Pseudomonas otitidis and P. stutzeri. Enrichment with both compost and nitrogen fertilizer enhanced the dissipation of TPH. Overall, compost-treated soils exhibited the highest degradation rates, with half-life (T½) values ranging from 13 to 37 days. Urea-treated soils exhibited the lowest TPH T½ values among the soils treated with inorganic fertilizers. The addition of glucose to soils treated with inorganic nitrogen fertilizers retarded the degradation rate of TPH, with estimated T½values measurements ranging from 70 to 140 days. Different dissipation patterns were noted among the different n-alkane fractions, with short chain molecules (up to 14 carbon atoms) being rapidly reduced within the first 21 days, whereas long chain molecules were more recalcitrant. In summary, we demonstrated that Pseudomonas-like strains and in situ soil incorporation of compost derived from winery byproducts can be effectively used for the rapid bioremediation of soil heavily polluted with hydrocarbons.

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.

Effect of biochar on the fate of volatile petroleum hydrocarbons in an aerobic sandy soil

Biochar addition to soil is currently being investigated as a novel technology to remediate polluted sites. A critical consideration is the impact of biochar on the intrinsic microbial pollutant degradation, in particular at sites polluted with a mixture of readily biodegradable and more persistent organic pollutants. We therefore studied the impact of biochar (2% on dry weight basis) on the fate of volatile petroleum hydrocarbons in an aerobic sandy soil with batch and column studies. The soil–water partitioning coefficient, K d, was enhanced in the biochar-amended soil up to a factor 36, and petroleum hydrocarbon vapor migration was retarded accordingly. Despite increased sorption, in particular of monoaromatic hydrocarbons, the overall microbial respiration was comparable in the biochar-amended and unamended soil. This was due to more rapid biodegradation of linear, cyclic and branched alkanes in the biochar amended soil. We concluded that the total petroleum hydrocarbon degradation rate was controlled by a factor other than substrate availability and the reduced availability of monoaromatic hydrocarbons in the biochar amended soil led to greater biodegradation of the other petroleum compounds.