Bioremediation Of Crude Oil Contaminated Soil Research Articles

Evaluation of the potential of agricultural wastes-cattle manure and poultry manure for bioremediation of crude oil-contaminated soil

The Niger Delta region of Nigeria suffers from petroleum pollution, which affects ecosystem functioning and human health, which necessitates finding sustainable remediation options that utilize local resources. In this work, cattle manure (CM) and poultry manure (PM), which are primarily utilized as biofertilizer for agricultural purposes, were utilized to bioremediate crude oil-contaminated soil on a laboratory scale. In addition to being readily accessible, CM and PM are also sustainable bioresources that are host to a wide variety of microflora that can be used for bioaugmentation. At the end of the 1.5 month study, the impact of the amendments on speciated total petroleum hydrocarbons (STPH) in the range of nC10-nC40 was evaluated. A significantly higher STPH degradation of 36% in PM-amended soil was observed compared to CM-amended soil (23%); and only 1% degradation in enhanced by natural attenuation soil (RENA). The pre-dominant aliphatic fractions in the samples analyzed were nC16-nC35. In comparison to the CM amendment option, PM amendments achieved better bioremediation of these fractions. Moreover, the effect of biowaste ratio amendment to the contaminated soil showed that the ratio 1:1 (w/w) for both bioadmendments performed better than the ratio 1:2 (w/w), suggesting that the higher the amount of amendment to contaminated soil, the more effective the bioremediation. The results of this study demonstrate the potential of PM as a sustainable, affordable, and local bioremediation technique for recovering soil contaminated by crude oil in the Niger Delta.

A novel dehydrocoenzyme activator combined with a composite microbial agent TY for enhanced bioremediation of crude oil-contaminated soil

Bioaugmentation (BA) and biostimulation (BS) synergistic remediation is an effective remediation strategy for oil-contaminated soil. In this study, the optimal combination system of composite microbial agent TY (Achromobacter: Pseudomona = 2:1) and dehydrocoenzyme activator (NaNO3 (7.0 g/L), (NH4)2HPO4 (1.0 g/L), riboflavin (6.0 mg/L)) was screened. Under the best combination system, the degradation rate of crude oil in oil-contaminated soil reached 79.44% after 60 d, which was 1.74 times and 1.23 times higher than that of compound microbial agent TY treatment and dehydrogenase activator treatment, respectively. In addition, a highly efficient combination system was found to target the degradation of oil C10–C28 fractions by gas chromatography (GC). The increased abundance of dehydrogenase coenzymes such as flavin nucleotides (FAD and FMN), coenzyme I (NAD+, Co I) and coenzyme II (NADP+, Co II) as well as dioxygenases and monooxygenases promote the degradation of crude oil. Furthermore, the dominant genera at the genus level in soil were analyzed by high-throughput sequencing, which were Nocardioides (46.48%–56.07%), Gordonia (11.40%–14.61%), Intrasporangiaceae (5.05%–10.58%), Pseudomonas (1.39%–1.92%) and Dietzia (0.64%–2.77%). Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis showed that the abundance of genes associated with crude oil degradation such as ABC transporters (2.89%), fatty acid (1.04%), carbon metabolism (4.5%) and aromatic compound (0.92%) was assigned enhanced after 60 d of remediation. These results indicated that the combination system of the compound bacterium TY and the dehydrocoenzyme activator is a propective option for the bioremediation of oil-contaminated soil.

Bioremediation of Crude Oil-Contaminated Soil using Compost as Bio-Stimulant

This study was conducted to investigate the usability of compost as a stimulant for the remediation of crude oil-contaminated soil. 2kg of porous sandy soil was measured into six different equal-sized cells and contaminated with 250 ml of sample crude oil. Masses of solid waste comprising of compost and sawdust were measured in varying amounts of 900g, 750g, 600g, 450g, 300g, and a control sample that had no compost and sawdust. The set-up was left to stand for eight weeks and the residual hydrocarbon content (RHC), pH, and total microbial count (TMC)of these samples were monitored and recorded. The percentage of hydrocarbon degradation that occurred in the treatment cells were; 33.11, 32.2, 31.2, 29.46 and 28.05 respectively, for the individual cells in the order above, while the control had a degradation rate of (0.44%) of the total hydrocarbon content after 8 weeks. pH values varied slightly within the ranges of 6.5-7.5. The TMC average values were 21, 188, 17,125, 15,000, 14,250, 13,125 and 0.1, with the highest count occurring in the sample having 900g of solid waste; followed by the other samples having lesser quantities of solid waste with the least value in the control. The resultant descent in TMC across each of the samples was due to the distribution of waste material in the samples, and the pH of the resulting mixtures remained at optimum, thereby favouring microbial growth across the samples.

Rhamnolipid-modified biochar-enhanced bioremediation of crude oil-contaminated soil and mediated regulation of greenhouse gas emission in soil

The application of biochar to contaminated soil is an effective strategy to enhance soil remediation by promoting microbial activity. However, the insufficient bioavailability of petroleum in crude oil-contaminated soil limits its application in contaminated soil. Biosurfactant could improve the remediation efficiency of contaminated soil by improving the bioavailability of petroleum in crude oil-contaminated soil. The combination of rhamnolipid and biochar was used to improve the bioremediation efficiency in bioremediation of oil-contaminated soil. Here, three types of biomass were applied to produce biochar including rice husk (BC), sewage sludge (SC), and petroleum coke (PC). Rhamnolipid was used to modify biochar for assessing their effect in bioremediation of oil-contaminated soil. The rhamnolipid-modified biochar was added to oil-contaminated soil with loading rate of 2% (wt/wt) for a 3-month experiment. Soil properties, greenhouse gas (GHG) emission, and microbial community compositions were characterized. The application of rhamnolipid-modified biochar exhibited better performance regarding the degradation of petroleum hydrocarbons, diversity, and abundance of microbial communities and degradation of n-alkanes and PAHs than pristine biochar. Besides, the application of biochar played an important role in the bioavailability of indigenous microbial communities for biodegrading of short-chain hydrocarbon. Meanwhile, the biochar amendments increased the emission of CO2 and CH4, while reduced the emission of N2O. The application of rhamnolipid-modified biochar could improve the diversity and abundance of microbial communities and then promote the degradation of n-alkanes and PAHs, providing an effective approach for bioremediation of crude oil-contaminated soil.

Performance and Kinetics of Bioaugmentation, Biostimulation, and Natural Attenuation Processes for Bioremediation of Crude Oil-Contaminated Soils

Bioremediation of contaminated sites is usually limited due to the inadequate availability of nutrients and microorganisms. This study was conducted to assess the impact of bioaugmentation (BA) and biostimulation (BS) on petroleum hydrocarbon degradation efficiency. In addition, treatment performance and kinetics of different remediation processes were investigated. For this purpose, four tanks containing oil-contaminated soils were tested. Tank 1 was operated as the natural attenuation process. Then, a microbial inoculum and nutrients were added to tank 2 to promote BA and BS. In tank 3, only the BA process was adopted, whereas in tank 4, only the BS process was adopted. After 63 days of operation, the total petroleum hydrocarbon (TPH) in tank 2 was reduced from 1674 to 430 mg/kg, with 74% reduction. Tank 1, tank 3, and tank 4 indicated TPH reductions of 35%, 41%, and 66%, respectively. Microbiological analysis of the inoculum indicated that Alcanivorax was the dominant bacterium. The population of TPH degrader bacteria in tank 2 soil was two orders of magnitude higher than in the control tank. Reaction rate data were fitted with a first-order reaction rate model. The Monod kinetic constants, maximum specific growth rate (µmax), and substrate concentration at half-velocity constant (Ks) were also estimated. This study showed that the TPH removal efficiency in the combined BA and BS process was higher than in other processes tested. The populations of TPH degrading microorganisms in soil tanks were positively related to TPH removal efficiency during bioremediation of petroleum-contaminated soils.

Diagnosing bioremediation of crude oil-contaminated soil and related geochemical processes at the field scale through microbial community and functional genes

PurposeBioremediation is widely considered the most desirable procedure for remediation of oil-contaminated soil. Few studies have focused on the relationships among microbial community, functional genes of biodegradation, and geochemical processes during field bioremediation, which provide crucial information for bioremediation.MethodsIn the current study, the microbial community and functional genes related to hydrocarbon and nitrogen metabolism, combined with the soil physico-chemical properties, were used to diagnose a set of bioremediation experiments, including bioaugmentation, biostimulation, and phytoremediation, at the field scale.ResultThe results showed that the added nutrients stimulated a variety of microorganisms, including hydrocarbon degradation bacteria and nitrogen metabolism microorganisms. The functional genes reflected the possibility of aerobic denitrification in the field, which may be helpful in biodegradation. Biostimulation was found to be the most suitable of the studied bioremediation methods in the field.ConclusionWe offer a feasible approach to obtain useful bioremediation information and assist with the development of appropriate remediation procedures. The findings improve our knowledge of the interactions between microorganisms and edaphic parameters.

Bio-stimulation Approach in Bioremediation of Crude Oil Contaminated Soil Using Fish Waste and Goat Manure

Aim: This study aimed to evaluate the ability of Fish waste and Goat manure to bio-stimulate the degradation process during bioremediation of crude oil-contaminated soil.
 Study Design: Research was designed to evaluate and compare the strength of the organic nutrients (Goat manure and fish waste)   to stimulate the biodegradation of crude oil contaminated soil within 56 days.
 Place and Duration of Study: Study was carried out in Rivers State University Farm, Rivers state, Nigeria for 56 days from July to September 2018.  Analyses were carried out weekly (per 7 days interval).
 Methodology:  Eight (8) experimental set-up were employed, each having 5kg farm soil, all were left fallow for 6 days before contamination with crude oil on the 7th day in the respective percentages. Four of the set-ups were contaminated with 5% Crude oil while the other four were contaminated with 10% Crude oil. The contaminated plots were further allowed for 21 days for proper contamination and exposure to natural environmental factors to mimic a crude oil spill site before the application of bio stimulating agents (fish waste and goat manure). The set-ups of 5% Crude Oil Contaminated Soil (5% COCS) and 10% Crude Oil Contaminated Soil (10% COCS) were then stimulated with nutrient organics; Goat Manure (GM) and Fish Waste (FW) except two setups (one 5% COCS and the other 10% COCS) which were used as controls. The treatments (setups) were as follows: 5% COCS    (control 1), 5% COCS + GM, 5% COCS + FW, 5% COCS + GM + FW and 10% COCS (Control 2), 10% COCS +GM, 10% COCS + FW, 10% COCS + GM + FW. Physiochemical and microbiological status of the soil before and after contamination was evaluated while parameters including Nitrate, Sulphate, Phosphate and Total Petroleum Hydrocarbon (TPH), as well as Microbial analyses, were monitored throughout the experimental period. Bioremediation efficiency was estimated from percentage (%) reduction of Total Petroleum Hydrocarbon (TPH) from day 1 to the residual concentration at day 56 of bio-stimulation setups with the control. The bio-stimulating potentials of goat manure and fish waste were compared using statistical tools.
 Results: The results revealed decrease in TPH with increasing time. The Amount (mg/kg) and Percentage (%) of Total  Petroleum  Hydrocarbon (TPH) remediated within the period of this study for 5% Crude Oil Contaminated Soil were as follows: 5% COCS-Ctrl 1 (563.52 mg/kg; 8.60%) < 5% COCS + GM (3608.84 mg/kg; 55.11%) < 5% COCS + FW (4156.49 mg/kg; 63.47%)  < 5% COCS + GM + FW (4350.69 mg/kg; 66.44%) while 10% crude oil contaminated soil were: 10% COCS-Ctrl 2 (125.71 mg/kg; 1.21%) < 10% COCS + GM (4422.75 mg/kg; 42.82%) < 10%COCS + FW (5542.16 mg/kg; 53.66%) < 10% COCS + GM + FW (6168.66 mg/kg; 59.72%). This result shows that combination treatment with goat manure and fish wasteis more effective and has more bio-stimulating potentials than the single treatments. With respect to individual bio-stimulating agent, fish waste proves more effective and had a higher bioremediation efficiency than goat manure. The results of colonial counts obtained revealed that the total heterotrophic bacterial and total fungal counts generally increased during the study across the trend. The counts obtained from day 7 to 56 in the respective experimental set ups were as follows: Total Heterotrophic Bacteria  counts increased from 6.32 to 8.20 Log10CFU/g (Control) < 6.32 to 9.05 Log10CFU/g  (COCS+FW) < 6.41 to 9.13 Log10CFU/g (COCS+GM) < 6.32 to 9.58 Log10CFU/g (COCS+FW+GM). Similar progression was observed for total fungi, hydrocarbon utilizing bacteria and hydrocarbon utilizing fungi in all the experimental set ups although irregular differences were observed in the control set ups.
 Conclusion: The combination of organic nutrient such as goat manure and fish waste as bio-stimulating agents have shown to have higher percentage (%) bioremediation efficiency than when applied singly. It was also observed that the microbial biomass increased with time; moreover the nutrient monitoring analysis revealed a continuous gradual increase of the soil nutrient as bioremediation increases with time. The nutrient inherent in the bio-stimulating agents’ fish waste and goat manure resulted in increased soil nutrient (from day 7 to 56) as bioremediation period increase thereby enhancing soil nutrients at end of experiment. It is therefore recommended that bio-stimulating agents such as fish waste and goat manure should be employed in bioremediation of crude oil-contaminated soil especially due to its soil nutrient enhancement after bioremediation exercise. It’s a very good nutrient amendment option.

[Improving Bioremediation of Crude Oil-contaminated Soil by Mild Pre-oxidation].

To obtain a mild Fenton pre-oxidation method, which could promote the efficient degradation of total petroleum hydrocarbons (TPH) in subsequent bioremediation, the differences in the characteristics of the hydroxyl radical (·OH), nutrient consumption, activity of indigenous bacteria (CO2), and TPH removal were investigated during subsequent bioremediation after different Fenton pre-oxidation treatments. The results showed that high biodegradation of TPH was observed after mild Fenton pre-oxidation (·OH existence time:73 h; H2O2 concentration:225 mmol·L-1), because of the high activity of residual bacteria. Moreover, the same TPH removal with the addition of bacteria could be achieved without adding bacteria (the TPH removal rate 38%) because the activity of the residual bacteria was strong after mild Fenton pre-oxidation. Under the condition of no additional bacteria source, mild Fenton pre-oxidation TPH removal (approximately 38%) was higher than that after ordinary Fenton pre-oxidation (15.32%-33.15%). Further analysis of the removal efficiency of each chain of hydrocarbons revealed that the mild pre-oxidation group could reduce the inhibition of the chain hydrocarbon components (C17-C21) in the subsequent bioremediation stage. Comparing the activity of the indigenous bacteria in each group, revealed that mild pre-oxidation could appropriately stimulate the growth and increase the activity of indigenous microorganisms, all of which are beneficial to the removal of TPH.

Analysis and optimization processes of goat dung as a potential co-substrate in bioremediation

The present study investigates the analysis and optimization processes of crushed Goat Dung (GD) as a potential co substrate in bioremediation of crude oil contaminated soil (COCS). The first order crude oil (CO) degradation kinetics and biological half-life with the effects of process parameters (pH and initial CO concentration) were also investigated. Results obtained from the effects of process parameters showed that 70 and 75% of CO were degraded at pH 7 and initial CO concentration of 130 g/l. The first order CO degradation kinetics and half-life indicated that the highest CO degradation rate constant and lowest half-life was obtained at 130 g/l. The optimum values of the independent variables as indicated by response surface methodology (RSM) were pH (6.8), temperature (39.5 °C) and CO concentration (85.2 g/l). Good relation between the R2 (98.60%), adjusted R2 (97.05%) and predicted R2 (90.88%) indicated the satisfactory performance of the second order quadratic model. The findings of this present work suggest that GD could be an effective CO substrate in bioremediation of COCS.

Exploring the novel indigenous strains for degrading the crude oil contaminants in soil sample

Soil hydrocarbon pollution often causes the crop quality and safety issue. Therefore, a high priority is given to exploring the novel bacterial strain to sustainable green agricultural food products. Two novel crude oil-degrading bacteria were screened from the local oil-contaminated soil, which exhibited a good emulsifying capacity in their oil spreading test, showing their most clearing zone on the oil covering petri dish. Glycolipid bio-surfactant was identified by the thin-layer chromatography analysis. Gas chromatography and ultraviolet spectrophotometer (UV) methods were used to evaluate the degradation degree of alkanes and aromatic hydrocarbons in crude oil. The biodegradation ability of a single strain was inferior to mixed strains. The latter revealed that the degradation of the crude oil was 92% and 85%, respectively, when cultured at 32 °C, 150 rpm for 20 days. The hardest degraded isoprenoid alkane (pristane) could easily be degraded by these mixed strains. The effect of cadmium (Cd) on the growth of isolated strains was also studied, and the results demonstrate that crude oil-degrading bacteria isolated in the present study have shown strong endurance to Cd2+ (IC50 were 228.80 mg L−1 and 97.74 mg L−1) for Pseudomonas aeruginosa Dut-lxm0725 and Rhodococcus erythropolis Dut-lxm1018 strains, respectively. The above results suggest that present wild strains could have a good application prospect in bioremediation of crude oil-contaminated soil.

Effect of Fenton pre-oxidation on mobilization of nutrients and efficient subsequent bioremediation of crude oil-contaminated soil

Fenton pre-oxidation and a subsequent bioremediation phase of 80 days were used to investigate the importance of matching concentration of residual indigenous bacteria and nutrient levels on subsequent bioremediation of crude oil. Experiments were performed using either high (>107.7 ± 0.2 CFU/g soil) or low (<105.9 ± 0.1 CFU/g soil) concentrations of bacteria and three different nutrient levels: enough (C/N > 9.8), moderate (C/N:5–9.8), and lacking nutrient level (C/N < 5) conditions. Weak Fenton pre-oxidation (225 mM H2O2 and 2.9 mM Fe2+) resulted in highly matching between nutrient level and the population of residual indigenous bacteria. Up to 53% of total petroleum hydrocarbon (TPH) and 58% of main hydrocarbon (C15C25, during the first 10 days) were removed from the soil. Under matching conditions, the activity of indigenous bacteria and nutrient mobilization were enhanced, promoting the bioremediation of crude oil. In addition, the biodegradation of long chain molecules (C26C30) required a high level of NH4+-N.

Impact of chemical oxidation on indigenous bacteria and mobilization of nutrients and subsequent bioremediation of crude oil-contaminated soil

Fenton pre-oxidation provides nutrients to promote bioremediation. However, the effects of the indigenous bacteria that remain following Fenton oxidation on nutrient mobilization and subsequent bioremediation remain unclear. Experiments were performed with inoculation with native bacteria and foreign bacteria or without inoculation after four regimens of stepwise pre-oxidations. The effects of the indigenous bacteria remaining after stepwise oxidation on nutrient mobilization and subsequent bioremediation over 80 days were investigated.After stepwise Fenton pre-oxidation at a low H2O2 concentration (225×4), the remaining indigenous bacterial populations reached their peak (4.8±0.17×106CFU/g), the nutrients were mobilized rapidly, and the subsequent bioremediation of crude oil was improved (biodegradation efficiency of 35%). However, after stepwise Fenton pre-oxidation at a high H2O2 concentration (450×4), only 3.6±0.16×103CFU/g of indigenous bacteria remained, and the indigenous bacteria that degrade C15–C30 alkanes were inhibited. The nutrient mobilization was then highly limited, and only 19% of total petroleum hydrocarbon was degraded. Furthermore, the recovery period after the low H2O2 concentration stepwise Fenton pre-oxidation (225×4) was less than 20 days, which was 20–30 days shorter than with the other pre-oxidation treatments. Therefore, stepwise Fenton pre-oxidation at a low H2O2 concentration protects indigenous bacterial populations and improves the nutrient mobilization and subsequent bioremediation.

Ammonium Oxidizing Bacteria Activity and Nitrification Rate in Oil Contaminated Wetland Soil under Remediation with Nutrient Supplements and Leguminous Plants

Previous investigation on the impact of crude oil on the growth of tropical legumes and its effect on nitrogen dynamics in wetland ultisol showed that oil contamination reduced N uptake by plants but increased N accumulation in soil microbial biomass. Moreover, the presence of hydrocarbons widened the C/N ratio in soil and led to more available N being immobilized by soil microorganisms. The present study was carried out to evaluate the activity of ammonium oxidizing bacteria (AOB) and their nitrification potential rate (NPR) in wetland soil under a remediation course. Mineralization studies showed that ammonium-N levels decreased while nitrate-N increased progressively in the uncontaminated soil (control) cultivated with leguminous plants (cover crops) during the 12 weeks remediation period. However, the remediated soils were affected in different ways. The experimented soil cultivated with Centrosema pubescens had higher mineral nitrogen (NH4-N, NO3-N, NO2-N, Total N and P) than soil cultivated with Calopogonium mucunoides and Pueraria phaseoloides. AOB counts recorded were in the ranged, 2.25 × 102 - 2.66 × 105, 2.31 × 102 - 2.11 × 104 and 4.25 × 102 - 2.98 × 104 respectively. The highest NPR was found in uncontaminated soil (11.68 - 60.92 nmol N/g dry weight soil (DWS)) followed by soil treated with poultry manure (9.65 - 24.86 nmol N/g DWS/h), NPK (7.88 - 39.45 nmol N/g DWS/h) and in the oil-contaminated soil (0.11 - 1.87 nmol N/g DWS/h). The relations between NH4-N concentration and NPR in soil cultivated with Centrosema (r = 0.852), Calopogonium (r = 0.745) and Pueraria (r = 0.722) were positively significant at 95% confidence limit. Similarly the relations between AOB density and NPR for Centrosema (r = 0.654; P = 0.05), Calopogonium (r = 0.588; P = 0.05) and Pueraria (r = 0.518; P = 0.05) were significant. The findings imply that nitrification potential of crude oil- contaminated soil differs significantly with the nutrient amendment/treatment technique adopted for remediation. Our research has shown that treatment of uncontaminated soil with cover crops increased AOB and nitrification rate. More so, contaminated soil treated with poultry manure and NPK-fertilizer, cultivated with covers crops resulted in remarkable reduction in hydrocarbons content and increased population of nitrifiers and nitrification potential rates of wetland soil over time. However, contaminated soil treated with poultry manure and cultivated with Centrosema pubescens is more effective in bioremediation of crude oil-contaminated soil.

Cold-adapted bacteria for bioremediation of crude oil-contaminated soil

BACKGROUND There are many cold climate terrestrial sites contaminated with petroleum hydrocarbons. Successful bioremediation in these regions relies heavily on suitable microorganisms with biodegrading capability at low temperatures. This work aims at screening cold-adapted bacteria strains and examining their capability of biodegrading petroleum contaminants. RESULTS Eleven strains of cold-adapted bacteria were isolated from oily sludge taken from a cold environment. Three strains, identified as Chryseobacterium, Bacillus and Pseudomonas, respectively, demonstrated high efficiency in biodegradation of crude oil pollutants based on the growth curves and oil removal rate. The optimal degradation conditions of the three bacteria were 10 °C, pH 7 and salinity of 10 g L−1 for a crude oil concentration at 1000 mg L−1. Under these conditions, the oil removal of the three bacteria after 8 days was 62.3, 61.6 and 60.9%, respectively. The strains were applied in simulated bioremediation tests using artificial contaminated soil containing 5.8–10.6 g oil kg−1 soil and achieved 61–78% oil removal after 150 days of bioremediation at 10 °C. CONCLUSION The three cold-adapted bacteria strains are capable of degrading crude oil efficiently at low temperatures and thus are suitable for bioremediation of petroleum contaminated soils in cold environments. © 2015 Society of Chemical Industry

Biodegradation of Crude Oil in Contaminated Soils by Free and Immobilized Microorganisms

The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study. Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained from the soil contaminated with crude oil in the Yellow River Delta. Then, the microbial cells were immobilized in sodium alginate (SA) beads and sodium alginate-diatomite (SAD) beads. The biodegradation of crude oil in soil by immobilized cells was compared with that by free cells at three inoculation concentrations, 1 × 104 colony forming units (cfu) kg−1 (low concentration, L), 5 × 104 cfu kg−1 (medium concentration, M), and 1 × 105 cfu kg−1 (high concentration, H). At 20 d after inoculation, the maximum degradation rate in the immobilized systems reached 29.8% (SAD-M), significantly higher (P < 0.05) than that of the free cells (21.1%), and the SAD beads showed greater degradation than the SA beads. Moreover, both microbial populations and total microbial activity reached significantly higher level (P < 0.05) in the immobilized systems than free cell systems at a same initial inoculation amount. The scanning electronic microscope (SEM) images also confirmed the advantages of the immobilized microstructure of SAD beads. The enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for bioremediation of crude oil-contaminated soils in the Yellow River Delta.

English

Microbial degradation of Tapis crude oil contaminated soil by&nbsp;Acinetobacter baumanniiT30C was conducted to evaluate the efficiency of the selected potential hydrocarbon degrader in stimulating bioremediation of crude oil-contaminated soil with different treatment units in microcosms with 2.5 kg soil. Previously,&nbsp;A. baumannii&nbsp;T30C was isolated from a Tapis crude oil-contaminated soil of oil refinery plant, Terengganu, Malaysia. The reduction of residual hydrocarbons in the soil was observed for a period of about 35 days. The study showed that amendment of nutrients was needed for stimulating the growth of&nbsp;A. baumannii&nbsp;T30C and indigenous microorganism in assisting the degradation of residual hydrocarbons in the soil. &nbsp; Key words:&nbsp;Bioremediation, bioaugmentation, aliphatic hydrocarbons, amendment of nutrients.

Bioremediation of crude oil-contaminated soil: Comparison of different biostimulation and bioaugmentation treatments

Biostimulation with inorganic fertilizer and bioaugmentation with hydrocarbon utilizing indigenous bacteria were employed as remedial options for 12 weeks in a crude oil-contaminated soil. To promote oil removal, biocarrier for immobilization of indigenous hydrocarbon-degrading bacteria was developed using peanut hull powder. Biodegradation was enhanced with free-living bacterial culture and biocarrier with a total petroleum hydrocarbon removal ranging from 26% to 61% after a 12-week treatment. Oil removal was also enhanced when peanut hull powder was only used as a bulking agent, which accelerated the mass transfer rate of water, oxygen, nutrients and hydrocarbons, and provided nutrition for the microflora. Dehydrogenase activity in soil was remarkably enhanced by the application of carrier material. Metabolites of polycyclic aromatic hydrocarbons were identified by Fourier transform ion cyclotron resonance mass spectrometry.

Bioremediation of Crude Oil Contaminated Soil by Bioaugmentation of Pseudomonas fluorescens NS1

A feasibility study was conducted to evaluate the efficiency of Pseudomonas fluorescens NS1 bioaugmented to stimulate in situ bioremediation of crude oil-contaminated soil with different amendments in treatment units. Pure culture of P. fluorescens NS1 was isolated from a petroleum-contaminated soil. The rate of degradation of petroleum hydrocarbons by the indigenous soil microflora and in the presence of P. fluorescens NS1 was assessed with the addition of nutrients and bulking agents for a period of about 35 days. The study showed that addition of wheat bran as bulking agent rapidly enhanced bioremediation of crude oil-contaminated soil compared to amendments in other treatment units.