Crude Oil-contaminated Soil Research Articles

Sustainable remediation of acid mine drainage (AMD)- and crude oil-contaminated sites through wastewater-enhanced Pseudomonas aeruginosa ATCC 15442 treatment

The increasing rate of soil contamination poses a major challenge to the sustainability of the ecosystem. Acid mine drainage (AMD) and crude oil are among the major soil contaminants contributing to the degradation of soil organic matter. This study aims to evaluate the application of Pseudomonas aeruginosa ATCC 15442 (PA-15442) and wastewater for the treatment of AMD- and crude oil-contaminated soils. A microcosm containing 1 kg each of AMD- and crude oil-contaminated soils was inoculated with PA-15442, and brewery and domestic wastewater were added for the bioaugmentation study. The result of the 28-day study conducted under mesophilic conditions showed an average TPH and metal removal efficiency of 58.84% and 52.75%, corresponding to 51.07, 47.29, 59.32, 58.98, and 47.1% for the individual metals (Fe, Al, Cu, Zn, and Mn), respectively, and 49% for the average sulfate removal after the treatment period. This study has shown that bioaugmentation of contaminated soils with the strain of PA-15442, and the addition of wastewater could be an environmentally friendly and sustainable approach for the remediation of AMD- and petroleum-contaminated soils.Graphical

Polycyclic aromatic hydrocarbons (PAHs) in crude oil-contaminated water and soil and their removal using locally available plant materials

ABSTRACT The presence of polycyclic aromatic hydrocarbons (PAHs) in water and soil can be harmful to human life when ingested. PAHs are determined in the water and soil of the B-Dere community of Rivers State, Nigeria. The extent of risk and source identification were carried out. The water samples were treated with garlic and Moringa seed extracts, while the soil samples were treated with garlic and Fenton oxidation reagents. PAHs were extracted before and after treatment. The gas chromatograph mass spectrometer analyses showed 13 PAHs in the water and 10 PAHs in thesoil. The highest concentration in water was recorded for benzo(ghi)perylene, with a mean value of 27.7 ± 0.25 ngL−1, while that of soil was recorded for benz(a)anthracene, with a mean value of 14.4 ± 0.631 ngkg−1. The source of PAHs in water was pyrogenic, while that of soil was petrogenic. Garlic extract removed 100% of benz(a)anthracene and benzo(b)fluorothane from the water, while Moringa removed 100% biphenylene from the water. However, garlic extract removed 2.59% of acenaphthylene, while Fenton reagents removed 100% of anthracene, phenathrene, and chrysene from the soil. Moringa seed and garlic extracts can be used in PAH's polluted water treatment.

The Impact of Organic and Chemical Organic Fertilizers on the Efficiency of Cadmium Mobility Reduction by Potassium Hydroxide Modified Biochar

The aim of this study was to investigate the impact of organic and chemical organic fertilizers on the translocation of cadmium in crude oil-contaminated soil treated with potassium hydroxide-modified biochar (KOH-biochar). The soil sample was collected from Chonburi Province. The soil was characterized as moderately acidic sandy loam with relatively low organic matter, medium salinity, medium cation exchange capacity, and high nutrient levels. The concentration of cadmium in the soil fell within the acceptable range for agricultural use. The KOH-biochar exhibited strong alkalinity, a high carbon/nitrogen (C/N) ratio, and an oxygen/carbon (O/C) ratio. Crude oil was slightly acidic, with high organic matter content and low sulfur and cadmium concentrations. The synthetic soil created in this study composed of 5% crude oil, and 100 mg/kg of cadmium. KOH-biochar, organic and chemical organic fertilizers were applied to this synthetic soil. Subsequently, the soil was subjected to extraction with 0.005 M diethylenetriamine pentaacetate (DTPA), and a sequential extraction method was employed to determine six different forms of cadmium in the soil samples. Cadmium concentrations in the extracts were measured using a graphite furnace atomic absorption spectrophotometer. The findings revealed that fertilizers effectively slowed down the movement of cadmium. Fertilizer application led to the transformation of cadmium from unstable forms to more stable forms within the soil. Fertilizer with the highest organic matter content and pH showed the least cadmium mobility. Increased nitrogen and phosphorus content in the fertilizer resulted in slightly higher cadmium mobility within the soil. Conversely, higher potassium content in the fertilizer led to slightly reduced cadmium mobility in the soil.

Phytoremediation of crude oil-contaminated soil using Vigna Unguiculata and associated rhizosphere bacteria

Persistent crude oil contamination poses a significant environmental challenge. In this study, the efficacy of Vigna unguiculata (L.) and associated rhizospheric microorganisms in remediating crude oil-contaminated soil within a microcosm setting was investigated. A randomized block design was employed, and soil samples were subjected to varying degrees of contamination: 0% (UR), 2.5% (CR2), 5.0% (CR5), 7.5% (CR7), and 10.0% (CR10) w/w crude oil. The investigation aimed to assess the potential of Vigna unguiculata (L.) in mitigating crude oil contamination across these defined contamination gradients. The plant growth and crude oil removal were monitored concurrently post-emergence. Plant emergence and growth were significantly affected due to contamination, especially among plants in CR5 and CR10. The bacterial population was higher in the rhizosphere, and the treatments with lower hydrocarbon contamination. It was shown that plant density encouraged the growth of bacterial communities. Significant reduction in soil TPH was observed in CR2 (76.61%) and CR7 (65.88%). There was a strong correlation between plant growth and oil-utilizing bacterial population (r2 = 0.966) and plant growth and hydrocarbon reduction (r2 = 0.956), signifying the role of plant-bacterial synergy. Saturate fractions (C30 – C32) were significantly degraded to lower molecular weight compounds (C11 – C14). Except in CR5 and CR10, the remediation within the cowpea rhizosphere was effective even at regulatory standards. Understanding the rhizosphere ecological dynamics would further highlight the role the bacteria played; hence, it is recommended.

Heterotrophic activity and hydrocarbon degradation in crude oil-contaminated coastal soil augmented with indigenous biosurfactant producing Pseudomonas sp.

The enhanced bioremediation of the petroleum-contaminated soil from the Ibeno coastal area was investigated using standard microbiological and biotechnological methods. Soil samples were simulated with 200ml, 400ml, and 800ml of Bonny Light crude oil representing 5%, 10%, and 20 % contamination levels respectively, and allowed to mimic natural crude oil degradation for 48 hours. The contaminated soil was bioaugmented with 15 ml of 24-hour culture of potent biosurfactant-producing bacteria – Pseudomonas aeruginosa with a viable cell count of 2.6 x 103 CFU/ml and monitored for 12 weeks. Analysis of the fate of the hydrocarbon contamination in soil augmented with the biosurfactant-producing pseudomonad revealed that the degradation of total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbons (PAHs) was faster in augmented soils. At the end of the degradation, the augmentation process induced a reduction in the TPH content and PAH levels of soil exposed to 20% contamination from 32.85 mg/kg to 15.14 mg/kg and from 16.34 mg/kg to 5.35 mg/kg respectively. These represent 45.9% and 32.7% remediation rates of TPH and PAH, respectively. The findings of this study also indicate that bioaugmentation of crude oil-contaminated soil with a culture of P. aeruginosa, does not only influence the density of heterotrophic and hydrocarbon-degrading bacteria in the soil but increases the natural attenuation potentials of the contaminated soil.

Synthesis of iron-manganese bimetallic materials supported by activated carbon and application of activated persulfate in the degradation of soil contaminated by crude oil

Heterogeneous catalytic processes based on zero-valent iron (ZVI) have been developed to treat soil and wastewater pollutants. However, the agglomeration of ZVI reduces its ability to activate persulfate (PS). In this study, a new Fe–Mn@AC activated material was prepared to activated PS to treat oil-contaminated soil, and using the microscopic characterization of Fe–Mn@AC materials, the electron transfer mode during the Fe–Mn@AC activation of PS was clarified. Firstly, the petroluem degradation rate was optimized. When the PS addition amount was 8%, Fe–Mn@AC addition amount was 3% and the water to soil ratio was 3:1, the petroluem degradation rate in the soil reached to the maximum of 85.69% after 96 h of reaction. Then it was illustrated that sulfate and hydroxyl radicals played major roles in crude oil degradation, while singlet oxygen contributed slightly. Finally, the indigenous microbial community structures remaining after restoring the Fe–Mn@AC/PS systems were analyzed. The proportion of petroleum degrading bacteria in soil increased by 23% after oxidation by Fe–Mn@AC/PS system. Similarly, the germination rate of wheat seeds revealed that soil toxicity was greatly reduced after applying the Fe–Mn@AC/PS system. After the treatment with Fe–Mn@AC/PS system, the germination rate, root length and bud length of wheat seed were increased by 54.05%, 7.98 mm and 6.84 mm, respectively, compared with the polluted soil group. These results showed that the advanced oxidation system of Fe–Mn@AC activates PS and can be used in crude oil-contaminated soil remediation.

Feasibility of microwave remediation of simulative crude oil-contaminated soil assisted by bluecoke-based modifiers

Microwave (MW) remediation of organics-contaminated soil technology offers the advantages of high efficiency and minimal damage, representing a new approach of soil thermal remediation. However, soil, being a weak MW-absorbing medium, struggles to convert MW energy into thermal energy, thus failing to attain the necessary temperature for thermal remediation. This paper prepared two new bluecoke (BC)-based modifiers (KHCO3@BC and KHCO3/MnO2@BC) to address temperature problem of MW remediation, as well as enhance soil quality. Their composition, structure and electromagnetic properties were analyzed to investigate their role in assisting with the MW remediation of an artificially crude oil-contaminated soil were investigated. Additionally, the industrial feasibility of MW remediation was addressed for the first time. The results showed that the KHCO3 and MnO2 particles in the two modifiers were covered on the BC surface and exhibited local agglomeration. Their carbon crystalline grain size increased, and the electromagnetic properties were weaker than those of the BC. Following 10 min of MW remediation assisted by KBC or KMnBC, the remediation temperatures exceeded 300 °C, with the removal rates of PHs reaching 76.16% and 88.31%, respectively. The organic matter content, soil potassium and mechanical fraction of the remediated soil were improved, but soil acidification still needed to be further addressed. The industrial application analysis indicated that the technical process and techno-economics of MW remediation of crude oil-contaminated soil were feasible, suggesting significant potential for the large-scale industrial application.

Sorption modelling of crude oil-contaminated soils using a derived spectral index

Theoretical models to describe and evaluate sorption of hydrocarbons on soil particles are well documented but experimental results in the literature are scarce. This study describes the use of a spectral index to evaluate sorption phenomena in oil-contaminated soils at micro and macro levels. Experiments involved oil-dosing from 0.25 mL to 4 mL and the application of a spectral index to estimate the sorption capacity of different soils based on change in statistically derived Critical Point (CP). Results show that sorption of oil varies with soil type, specifically the proportion of clay in a soil/sediment and the clay species, in the order smectite > illite > kaolinite. In support of theoretical models, this work proposes a model from experimental data that explains observed phenomena of soil-oil interaction with changing soil composition. The location and prominence of the CP is also strongly affected by soil moisture, particularly in coarse-grained soils, potentially providing insight to soil-oil–water interaction. The methods developed using a simple synthetic crude provide potential to explore other contamination scenarios including different soil compositions, types of petroleum products and different environmental controls.

Evaluating and modeling the efficacy of Stipagrostis plumosa for the phytoremediation of petroleum compounds in crude oil-contaminated soil

ABSTRACT This study focused on using Stipagrostis plumosa for phytoremediation to eliminate total petroleum hydrocarbons (TPHs) and heavy metals (HMs) like cadmium (Cd), chromium (Cr), lead (Pb), and nickel (Ni) from oil-contaminated soil. Conducted over six months at a field-scale without artificial pollutants, soil samples were analyzed using gas chromatography‒mass spectrometry (GC‒MS) for TPHs and inductively coupled plasma-optical emission spectroscopy (ICP‒OES) for HMs. Results after six months revealed that plots with plants had significantly higher average removal percentages for TPHs (61.45%), Cd (39.4%), Cr (46.1%), Pb (41.5%), and Ni (44.2%) compared to the control group (p <0.05). Increased microbial respiration and bacteria populations in planted plots indicated enhanced soil microbial growth. Kinetic rate models aligned well with the first-order kinetic rate model for all pollutants (R2 >0.9). Overall, the study demonstrates that S. plumosa can effectively reduce TPHs and HMs in oil-contaminated soil, making it a promising option for pollutant absorption.

ECOLOGICAL AND HUMAN HEALTH RISKS ASSOCIATED WITH SOIL POLLUTION BY PAHS AND HEAVY METALS IN THE NIGER DELTA

Despite the prevalence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in Niger Delta's crude oil regions, comprehensive research on their concentrations and combined risks in crude oil-contaminated soils is lacking. Our study focused on examining the concentration, source, spatial distribution, and health risk of 16 PAHs and 9different HMs in soils across a gradient of Niger Delta area Nigeria. The objective was to gain a comprehensive understanding of the HMs and PAHs' behavior in the environment and their potential impact on human health. The mean total concentrations of 16 PAHs (Σ16PAHs) were 779.58 ng/g for upland area, 749.46 ng/g for mid-slope area, and 679.37 ng g-1 for Low-land. The concentration of the HMs followed the order of Cu &gt; Cd &gt; Ni &gt; Pb &gt; Cr &gt; Fe &gt; Mn &gt; Zn &gt; Co, with Cu, Cd, Ni, and Pb exceeding the permissible levels. The study areas displayed varying concentrations of NO3-, PO42-, SO42- Ca, Na, and K, with some levels exceeding acceptable values, possibly influenced by crude oil contamination and the use of fertilizers. In the Niger Delta regions, the primary sources of soil PAH contamination include crude oil spills, natural crude oil seepage, and coal combustion. With this, the government of Nigeria should strengthen soil contamination monitoring, enforce spill regulations and promote eco-friendly farming.

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.

Combined impacts of bioaugmentation and vermiremediation on crude oil-contaminated soil: Mitigating strategies for prospective environmental management

This study aimed to address the remediation of crude oil-contaminated soil by employing four different factorial setups: I - used the earthworms (Eudrilus eugeniae) for vermiremediation, II – utilized the bacteria (Pseudomonas aeruginosa FA-7) for bioaugmentation, III – combined earthworms + bacteria to perform vermiremediation + bioaugmentation, and IV – served as abiotic control. Further, garden soil weighing 1 kg and 50 g of desiccated cow dung were introduced into the experimental groups and abiotic controls. Subsequently, different quantities of crude oil ranging from 5 to 20 mL were introduced. Based on the results, from 5 mL of oil-contaminated soil, the factorial setup-III removed the maximum proportion of total petroleum hydrocarbons (TPH) in V + B1 (58.06 %). The abiotic control treatments AC1 (1.11 %) exhibited the lowest TPH removal rate. The bioremediated soil had significantly (P < 0.05) different physicochemical properties than the initial crude oil contaminated soil. For instance, earthworm and microbial action resulted in considerable reductions in pH (4.72 %), total organic carbon (44.03 %), total nitrogen (42.42 %), total phosphorus (52.17 %), and total potassium (22.64 %) by the end of the day. On the 60th day of factorial setup-III, the bacterial population (386.470 ± 0.432 CFU × 106 g−1), actinomycetes (188.043 ± 0.246 CFU × 108 g−1), and fungi (16.603 ± 0.202 CFU × 105 g−1) were increased. The germination rates of Trigonella foenum-graecum seeds were increased by 86.6 % in factorial setup III (V + B1) when compared to other factorial setups. Hence, the incorporation of vermiremediation and bioaugmentation provides a distinctive platform for effective oil-contaminated soil remediation.

Characteristic microbiome and synergistic mechanism by engineering agent MAB-1 to evaluate oil-contaminated soil biodegradation in different layer soil.

Bioremediation is a sustainable and pollution-free technology for crude oil-contaminated soil. However, most studies are limited to the remediation of shallow crude oil-contaminated soil, while ignoring the deeper soil. Here, a high-efficiency composite microbial agent MAB-1 was provided containing Bacillus (naphthalene and pyrene), Acinetobacter (cyclohexane), and Microbacterium (xylene) to be synergism degradation of crude oil components combined with other treatments. According to the crude oil degradation rate, the up-layer (63.64%), middle-layer (50.84%), and underlying-layer (54.21%) crude oil-contaminated soil are suitable for bioaugmentation (BA), biostimulation (BS), and biostimulation+bioventing (BS+BV), respectively. Combined with GC-MS and carbon number distribution analysis, under the optimal biotreatment, the degradation rates of 2-ring and 3-ring PAHs in layers soil were about 70% and 45%, respectively, and the medium and long-chain alkanes were reduced during the remediation. More importantly, the relative abundance of bacteria associated with crude oil degradation increased in each layer after the optimal treatment, such as Microbacterium (2.10-14%), Bacillus (2.56-12.1%), and Acinetobacter (0.95-12.15%) in the up-layer soil; Rhodococcus (1.5-6.9%) in the middle-layer soil; and Pseudomonas (3-5.4%) and Rhodococcus (1.3-13.2%) in the underlying-layer soil. Our evaluation results demonstrated that crude oil removal can be accelerated by adopting appropriate bioremediation approach for different depths of soil, providing a new perspective for the remediation of actual crude oil-contaminated sites.

Biotechnological Potential of Oil-Tolerant Strains for Possible Use in Bioremediation

The release of oil into the environment represents a pervasive problem stemming from oil exploration, accidents, transportation and releases from landfills, storage facilities or industrial plants. Compared to conventional and costly techniques, bioremediation is an attractive and promising alternative, as it can selectively degrade pollution without affecting the natural features of the site and the flora and fauna living there. In this study, the isolation, identification and characterization of autochthonous bacterial strains from a crude oil-contaminated soil sample was carried out under batch conditions over a period of 28 days. The initial colony forming units value for bacteria was 1.15 × 109/g of soil. The results show that the activity of bacteria was highest at a pH of 7.25. Based on morphology, biochemical tests and an analysis of MALDI TOF, isolated autochthonous bacterial species were identified as Bacillus megaterium, Bacillus licheniformis, Bacillus cereus and Pseudomonas chlororaphis. Since allochthonous bacteria are not highly efficient in a new environment due to their low adaptability and competition with indigenous microorganisms, these autochthonous microorganisms play a pivotal role in enhancing the bioremediation process on an applicable, industrial scale. This advancement aligns with the principles of sustainable development and the green economy, as purified soil is suitable for rational reuse in the environment.

Heavy Metal Levels and Ecological Risk in Crude Oil-Contaminated Soils from Okpare-Olomu, Niger Delta, Nigeria

Heavy Metal Levels and Ecological Risk in Crude Oil-Contaminated Soils from Okpare-Olomu, Niger Delta, Nigeria

Effect of Charcoal and Active Carbon as Filter Media on Electrokinetic Remediated Crude Oil Contaminated Soil

Research has shown that traditional electrokinetic remediation (EKR) technology has limited efficiency against different contaminants and soils. This has led to the use of several strategies to enhance the traditional EKR for higher contaminants removal efficiency. This paper separately uses charcoal and active carbon each 1 cm thick as filter media in EKR to enhance the removal of crude oil from crude oil contaminated soil (COCS) containing 78,600 mg/kg of crude oil. The filters are placed very close to the anode compartment containing 0.01 M NaOH electrolytes. Graphite electrodes are used in a face to face configuration to pass 1 V DC/cm through the COCS. Crude oil removal efficiencies of 81.4% and 84.6% respectively are obtained from the EKR setups containing charcoal and active carbon filters after 18 days and 14 days of remediation respectively. This makes active carbon a better filter medium than charcoal for COCS. The results of the chemical oxides compositions show improvement from non-lateritic COCS to lateritic for the filter media enhanced EKR soil. Although active carbon has proven to be a better filter medium compared to charcoal for use in enhancing EKR technology for COCS. Nonetheless, with over 80% removal efficiency, charcoal or active carbon filters be used to enhance EKR remediation of COCS.

Potential biodegradation of polycyclic aromatic hydrocarbons (PAHs) and petroleum hydrocarbons by indigenous fungi recovered from crude oil-contaminated soil in Iran

A total of 265 fungal individuals were isolated from soils exposed to heavy oil spills in the Yadavaran oil field in Iran to discover indigenous fungal species with a high potential to biodegrade petroleum hydrocarbon pollutants. Morphological and molecular identification of obtained fungal species led to their assignment into 16 genera and 25 species. Alternaria spp. (78%), Fusarium spp. (5%), and Cladosporium spp. (4%) were the most common genera, along with Penicillium spp., Neocamarosporium spp., Epicoccum sp., Kotlabaea sp., Aspergillus sp., Mortierella sp., and Pleurotus sp. A preliminary screening using the DCPIP indicator revealed that approximately 35% of isolates from Alternaria, Epicoccum, Neocamarosporium, Cladosporium, Fusarium, Stachybotrys, Penicillium, and Stemphylium demonstrated promising tolerance to crude oil. The best-performing isolates (12 fungal individuals) were further investigated for their capacity to mineralize a mixture of four polycyclic aromatic hydrocarbons (PAH) for 47 days, quantified by GC–MS. Eventually, two top-performing isolates, namely 5c-12 (Alternaria tenuissima) and 3b-1 (Epicoccum nigrum), were applied to petroleum-contaminated soil. The GC–MS analysis showed that 60 days after inoculation, these isolates successfully degraded more than 70% of the long-chain hydrocarbons in the soil, including C8-C16 n-alkanes, C36 n-alkane, and Pristane. This study introduces two fungal species (5c-12 and 3b-1) with high potential for biodegrading petroleum compounds and PAHs, offering promising prospects for the decontamination of oil-contaminated soil.

Enhanced Phytoremediation and Physicochemical Parameters of Crude Oil Polluted Soil Using Pseudomonas fluorescens and Bacillus substilis

There have been worry over the Niger Delta's environmental contamination. Bacteria and other microorganisms have shown to be very helpful in the breakdown of hydrocarbons generated from petroleum. The goal of this research is to use elbow bufallow grass and sedge plants for phytoremediation of soil affected by crude oil. Standard microbiological techniques were applied to the contaminated soil once it was gathered. Using a hand auger, contaminated soil samples were taken twice a month for three months from two separate locations in Rivers State at two distinct depths: 0–15 cm and 15–30 cm. The following physicochemical parameters of samples were analysed using Standard Laboratory Procedures: pH, Temperature, Nitrogen, Phosphorus, Potassium available in the polluted soil and the total hydrocarbon content (THC). Two plant species common in the Ogoni region of Rivers state, i.e. Sedge plant (Schoenoplectus), Elbow buffalo grass (Panicum subalbidum) were used for phytoremediation monitoring. A combination of treatment consisting of the application of Pseudomonas fluorescens Bacillus substilis, Panicum subalbidum and Schoenoplectus senegalensis was evaluated during 28 days of remediation. Each pot contained crude oil mixture in the soil as a sole source of carbon and energy. THB counts ranged from 2.35 to 4.15 cfu/g. The statistical analysis revealed that there was no significant difference (p&gt;0.05) in the total heterotrophic bacteria counts between the samples. HUB counts range from 0.7 to 1.45cfu/g. The total bacterial population counts obtained from soil sample during bioremediation monitoring ranged from 17+1.41 (CS+PAN) to 40+1.412cfu/g (CS+PSE+BAC+PAN) in Day 1. Results of Day 14 range from 13+1.41 (CS+PAN) to 35.5+3.542cfu/g (CS+BAC+SCH). Results of Day 28 ranged from 8.5+0.71 (CS+PAN) to 27+1.412cfu/g (CS+PSE+BAC+PAN). The presence of microbial activity was determined by the enumeration and isolation of total heterotrophic and hydrocarbon utilizing bacteria. The results of physicochemical parameters before bioremediation is as follows: pH (5.43), Temperature (27oC), Electrical conductivity (9), Moisture content (7.80%), Total organic carbon (0.93%), Soil organic matter (1.60%), Nitrogen (56.695mg/kg), Phosphorus (0.621mg/kg), Potassium (7.125mg/kg) and Total Hydrocarbon content (700mg/kg). Results revealed amount of soil hydrocarbon removed and percentage (%) Bioremediation remediated after 28 days of monitoring to be higher in set up with CS+PSE+SCH (3454mg/kg; 85.28%) and lowest in set up with US+SCH (434mg/kg: 62%) and the amount of root hydrocarbon content removed and percentage (%) Bioremediation remediated after 28 days of monitoring to be higher in set up with CS+BAC+SCH (632Mg/kg; 15.6%) and lowest in set up with US+SCH (12.2mg/kg; 1.74%).&#x0D; Three (3) most occurring hydrocarbon utilizing bacterial isolates were isolated and identified culturally and phenotypically from the soil samples these bacteria isolates were confirmed to be Peudomonas, Priestia megaterium and Bacillus spp molecularly via sequencing of the 16SrRNA gene. The most common bacteria isolated were Bacillus spp at a dilution of 104. This research revealed and recommend that Panicum subalbidum as a suitable plant species for phytoremediation of crude oil-contaminated soil.

New insights of crude oil biodegradation construction by microbial consortium B10: Responded substrates, genomics, biodegradation mechanism and pathways

Crude oil pollution caused by production and living demands has existed for decades, which adverse to ecological security and human health. Microbial degradation of crude oil is a green and effective remediation method. This study is intended to develop a microbial consortium based on the commonness and differences of key genes and response substrates of the strains to efficiently degrade crude oil. Four crude oil-contaminated soil dwelling bacteria, CO1, CO2, CO6 and CO7, were isolated whose crude oil degradation and emulsification performance were evaluated. Subsequently, revealing their genomic characteristics and response substrates, the key genes of CO1 were mapped to genes alkB, hcaD; CO2 were located at genes andAd, andAc; CO6 were mapped to genes ladA, alkM, pcaH, benB-xylY and CO7 were located at gene cypd-E. Consortium of Ochrobactrum.sp, Pseudomonas aeruginosa and Bacillus.sp were selected as microbial consortium B10. Compared with single strain, the crude oil removal efficiency of B10 via RSM method optimizing is up to 51.58 % in 6 days, where the C11-C18 removal rate is up to 78.51 %. Besides, the biodegradation rates of C26-C29 and C33-35 increased by 36.20 % and 30.51 %, respectively. The possible metabolic pathways of crude oil were proposed, including aldehyde bond (H-C=O) and ketone bond (C-O-C) hydrodehydration, ring opening of cyclic ether, C-C bond oxidation of benzene ring and ring-opening hydrolysis of gentisic acid reactions. Altogether, this study provides a new insight into high-performance microbial consortia construction in crude oil biodegradation.

The effect of various environmental conditions on stabilization/solidification (S/S) of oil-contaminated soil using alkaline activation of granulated blast furnace slag (GBFS)

Alkali-activated materials (AAMs) have been proposed as sustainable alternatives to traditional stabilizers. This study investigated the effect of freeze-thaw and wet-dry conditions on the durability of oil-contaminated soil stabilized using alkaline activation of granulated blast furnace slag (GBFS). The effect of curing temperature on GBFS-based samples was also evaluated. The main goal was to provide a suitable platform for the use of this eco-friendly material to improve the durability of oil-contaminated soil. Based on unconfined compressive strength (UCS) results and micro and macro investigations, the formation and melting of ice lenses increased the freezing and thawing cycles of the holes and, as a result, the UCS of the GBFS-based samples decreased. As the wet-dry cycle increased to 3, the UCS rose and then decreased. Raising the amount of GBFS and reducing the amount of crude oil in the GBFS-based samples prevented a sharp decrease in UCS and improved durability by increasing the entanglement and connection of particles and creating a denser structure. Increasing the curing temperature by removing free water and accelerating the geopolymerization and hydration reactions caused a further rise in UCS. In general, this study showed the appropriate circumstances for using this stabilization method for crude oil-contaminated soils in different environmental conditions.