Total Petroleum Hydrocarbon Degradation Research Articles

Biogenic iron oxide nanoparticles and activated sodium persulphate for hydrocarbon remediation in contaminated soil

Biogenic iron oxide nanoparticles synthesized from a locally sourced, readily available plant — Azadirachta indica, were used synergistically with sodium persulphate (PS) to degrade total petroleum hydrocarbons (TPHs) in contaminated soil. A chemometric approach to optimizing the conditions for the degradation of TPH was developed using central composite design (CCD). Characterization of iron oxide nanoparticles was carried out with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected electron area diffraction (SAED). Analysis of TPH was carried out with gas chromatography flame ionization detector (GC-FID). The optimum condition for the complete degradation of TPH was achieved at pH 6.0 and oxidant dosage of 0.74 M within 14 h and 5 days. Iron nanoparticles AZA FeNP (1:1) and AZA FeNP (2:1) were synthesized by varying the ratio of extract/precursor. The nanoparticles displayed heterogeneous, amorphous morphology with increased agglomeration in AZA FeNP (1:1). AZA FeNP (2:1) XRD spectra exhibited characteristic peaks at 27.0°, 35.4° and 44.5°, which are attributed to iron nanoparticles. TEM and HR-TEM images confirmed spherical nanoclusters’ presence with an average size of 9.3 and 10.0 nm for AZA FeNP (1:1) and AZA FeNP (2:1), respectively. The EDX spectra displayed intense peaks of oxygen, carbon, and iron at 0.4, 0.6 and 6.4 KeV confirming the presence of FeNP. Under optimized conditions, PS alone degraded 68% TPH while 0.07 and 0.15 g/L FeNP achieved ∼93 and 95% degradation, respectively. Additionally, 0.07 and 0.15 g/L FeNP-activated PS achieved ∼99 and 100% TPH degradation, respectively. The outcome of these findings suggests that FeNP synthesized using A. indica successfully catalyzed PS for complete degradation of TPH in crude oil-contaminated soil.

Treatment of soil contaminated with petroleum hydrocarbons using activated persulfate oxidation, ultrasound, and heat: A kinetic and thermodynamic study

This study focuses on the remediation of petroleum hydrocarbons in the soil matrix. Factors such as the persulfate dosage, initial pH, temperature, ultrasonic power, and soil water ratio were investigated by using ultrasonic and thermal energy to activate persulfate. The results showed that the degradation efficiency of the total petroleum hydrocarbon (TPH) content was 78.2% and 72.64% within 72 h for the ultrasonically/thermally-activated persulfate (“US/Heat/PS”) and thermally-activated persulfate (“Heat/PS”) systems, respectively, whereas it was 56.41% for the ultrasonically-activated persulfate system. The results of the kinetics analysis suggested that the degradation of petroleum hydrocarbons well-fitted the pseudo-second-order reaction, and that the rate constants increased with increasing temperature and initial persulfate dosage but with decreasing pH over a certain range. Moreover, three reaction phases comprising two rapid phases and an intermediate phase were observed for the TPH degradation. The measured thermodynamic parameters justified the spontaneity of the degradation process. Furthermore, a possible mechanism of petroleum hydrocarbon degradation in the US/Heat/PS system was determined through gas chromatography–mass spectrometry analysis, and the degradation priority of different components was ranked as: alkenes > alcohols > esters > alkanes > aromatics.

Combined phyto-microbial-electrochemical system enhanced the removal of petroleum hydrocarbons from soil: A profundity remediation strategy

The soil contaminated by petroleum hydrocarbons has been a global environmental problem and its remediation is urgent. A combined phyto-microbial-electrochemical system (PMES) was constructed to repair the oil-contaminated soil in this study. During the 42-day operation time, a total petroleum hydrocarbons (TPHs) of 18.0 ± 3.0% were removed from PMES, which increased by 414% compared with the control group (CK1). The supervision of physicochemical properties of pore water in soil exhibited an enhanced microbial consumption of the total organic carbon (TOC) and N source under the applied potential with the generation of bio-current. The microbial succession indicated that the Dietzia, Georgenia and Malbranchea possibly participated in the degradation and current output in PMES. And a collaborative network of potential degrading microorganisms including unclassified norank_f__JG30-KF-CM45 (in Chloroflexi), Dietzia and Malbranchea was discovered in PMES. While the functional communities of microorganism were re-enriched with the reconstructed interactions in the system which was started with the sterilized soil (S+MEC). The superiority of TPHs degradation in S+MEC compared to P + CK2 (removing the electrochemical effect relative to CK1) revealed the key role of external potential in regulating the degradation microflora. The study provided a strategy of the potential regulated phyto-microbial interaction for the removal of TPHs.

PENGARUH PENAMBAHAN BIOCHAR TERHADAP PENURUNAN KADAR TOTAL PETROLEUM HYDROCARBON (TPH) PADA TANAH TERCEMAR MINYAK BUMI

Hydrocarbons are compounds produced as a result of the activities of the petroleum industry, which can pollute the soil and waters. Due to the amount of waste, biochar from agricultural waste could potentially be used as a soil amendment agent for hydrocarbon contamination. The high lignocellulose in oil palm shells and empty bunches makes them potential raw materials for biochar. The purpose of this study was to explore the effect of biochar application on petroleum-contaminated soil to reduce Total Petroleum Hydrocarbon (TPH) levels. In this study, the dosage of biochar was added to the soil contaminated with petroleum with a variation of 3%, 5%, and 7% (w/w) and control without the addition of biochar. The parameters analyzed were TPH levels by gravimetric method every week for four weeks. The results showed that the addition of biochar had an effect on the degradation of TPH. The greater the dose of biochar used, the higher the percentage of TPH degradation. The highest decrease in TPH levels occurred at the addition of biochar dose by 7%, where the empty shell was 60.65%, and empty bunches was 54.1% which was greater than without the addition of biochar by 32.79%.

Enhanced biodegradation of total petroleum hydrocarbons by implementing a novel two-step bioaugmentation strategy using indigenous bacterial consortium

In the present study, a two-step bioaugmentation strategy (TSBS) was implemented by using indigenous bacterial consortium to enhance the degradation of total petroleum hydrocarbons (TPH) from petroleum refinery sludge (PRS). A bacterial consortium was developed using four indigenous isolated strains, Dietzia sp. IRB191, Dietzia sp. IRB192, Staphylococcus sp. BSM19 and Stenotrophomonas sp. IRB19 from PRS. The optimum conditions of pH, temperature, and sludge concentration were 7, 34 °C, and 2% (w/v), respectively, for maximum TPH degradation, obtained using one variable at a time approach. Under the optimal culture conditions, the developed consortium was inoculated twice to the culturing medium, at the beginning (0th day) and again on the 10th day for implementing a novel TSBS. The maximum TPH degradation of 91.5 ± 2.28% was found with TSBS, which was 1.18 times higher than that of SSBS (77.3 ± 2.6%) in 15 days of incubation. GC-FID study also confirmed that the TPH present in the PRS was effectively degraded by the bacterial consortium with TSBS. The TPH degradation by using TSBS proceeded according to the first-order kinetics with a rate constant of 0.155 d−1. Hence, biodegradation using a TSBS can be considered an effective and eco-friendly process for safe disposal of petroleum refinery sludge.

Responses of oil degrader enzyme activities, metabolism and degradation kinetics to bean root exudates during rhizoremediation of crude oil contaminated soil

During rhizoremediation process, plant roots secrete the specific exudates which enhance or stimulate growth and activity of microbial community in the rhizosphere resulting in effective degradation of pollutants. The present study characterized cowpea (CP) and mung bean (MB) root exudates and examined their influences on the degradation of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) by the two oil degraders Micrococcus luteus WN01 and Bacillus cereus W2301. The effects of root exudates on soil microbial population dynamic and their enzymes dehydrogenase (DHA), and catechol 2,3 dioxygenase (C23O) activities were assessed. Both root exudates enhanced the degradation by both oil degraders. Cowpea root exudates maximized the removal of TPHs and PAHs by M. luteus WN01. Both bacterial population and DHA increased significantly in the presence of both root exudates. However, the C23O activities were significantly higher in WN01 treated. No significant influence of root exudates was observed on the C23O activities of W2301 treated. By using gas chromatography -mass spectroscopy, the dominant compounds found in cowpea and mung bean root exudates were 4-methoxy-cinnamic acid and terephthalic acid. Found in lower amount were propionic, malonic acid, and citric acid which were associated with enhanced PAHs desorption from soil and subsequent degradation. Novelty statement This is the first study to characterize the low molecular weight organic acids from root exudates of cowpea and mung bean and their influences on hydrocarbon desorption and hence enhancing the biodegradation process. The findings of the present study will greatly contribute to a better understanding of plant-microbe interaction in total petroleum hydrocarbons contaminated soil.

Assessing the Effect of Chemical Dispersant Nokomis 3-F4 on the Degradation of a Heavy Crude Oil in Water by a Marine Microbial Consortium.

Degradation efficiency of a heavy crude oil by a marine microbial consortium was evaluated in this study, with and without the addition of a chemical dispersant (Nokomis 3-F4). 15.50% of total petroleum hydrocarbons (TPH) were removed after 15days of incubation without dispersant, with a degradation rate of 2.39 ± 0.22mg L-1 day-1. In contrast, the addition of Nokomis 3-F4 increased TPH degradation up to 30.81% with a degradation rate of 5.07 ± 0.37mg L-1 day-1. 16S rRNA gene sequencing indicated a dominance of the consortium by Achromobacter and Alcanivorax. Nonetheless, significant increases in the relative abundance of Martelella and Ochrobactrum were observed with the addition of Nokomis 3-F4. These results will contribute to further environmental studies of the Gulf of Mexico, where Nokomis 3-F4 can be used as chemical dispersant.

Bio-electrocatalytic remediation of hydrocarbons contaminated soil with integrated natural attenuation and chemical oxidant

The present study aimed to assess the possibility of integrating natural attenuation (NA) and chemical oxidation (O) with the bio-electrocatalytic remediation (BET) process to remediate petroleum hydrocarbons contaminated soil. Six different reactors were operated, wherein in the first reactor was a NA system, and the second condition to the NA was supplemented with a chemical oxidant (NAO). These systems were compared with BET systems which were differentiated based on the position and distance between the electrodes. The study was performed by considering NA as a common condition in all the six different reactors viz., NA, NAO, NA + BET with 0.5 cm space amid electrodes (BETH-0.5), NAO + BET with 0.5 cm space amid electrodes (BETOH-0.5), NAO + BET with 1.0 cm space amid electrodes (BETOH-1.0), and NAO + BET with vertical electrodes at 1.0 cm distance (BETOV-1.0). The highest total petroleum hydrocarbons (TPH) degradation efficiency was observed with BETOH-0.5 (67 ± 0.8%) followed by BETOH-1.0 (62 ± 0.6%), BETH-0.5 (60%), BETOV-1.0 (56 ± 0.5%), NAO (46.6%), and NA (27.7%). In NA, the indigenous microorganisms remediate the organic contaminants. In the NAO system, KMnO4 actively breakdown the carbon-carbon double bond functional group. Further, in BETOH-0.5, an anodophilic bacteria enriched around the electrode reported enhanced treatment efficiency along with a maximum of 260 mV (1.65 mA). BET systems integrated with chemical oxidation processes were much more effective in the TPH removal process than an individual process. The BET method adopted here thus provides a good opportunity for bio-electrocatalytic remediation of TPH and resource recovery in the form of bioelectricity.

Hydrocarbon solubilisation by oil and cellulose-degrading Chitinophaga terrae isolated from the rumen.

This study investigated the capacity of cellulose and hydrocarbon degrading bacterium isolated from the rumen of a cow to solubilise hydrocarbon. The bacterium was isolated from the rumen fluid of cow and its capacity to degrade cellulose was screened on carboxyl methyl cellulose (CMC) agar plate and the ability to degrade crude oil was carried out using Bonny Light crude. Solubilisation of hydrocarbon was determined by carrying out emulsification index (E24) using kerosene. Other bio-surfactant characteristics such as blood haemolysis, tilted slide capacity and oil displacement were tested also. The bacterium was identified based on phenotypic, biochemical and molecular characteristics. The isolate achieved 48.17% degradation of total petroleum hydrocarbon (TPH) within 14 days with emulsification index of 54.5%. The isolate also produced clear zone on agar plate containing CMC as the sole carbon source. Phylogenetic tree analyses classified the bacterial isolate as Chitinophaga terrae. The sequences have been deposited to GenBank under the accession number KJ076216.1. This study has demonstrated that the novel strain of Chitinophaga terrae used in this study not only has the capacity for multiple substrate utilization, but also has the capacity to produce bio-surfactant. Considering that the isolate was obtain from the rumen of cow it shows that rumen content may harbour bacteria with diverse economical and ecologically-friendly product, which may be utilized for bioremediation of crude oil contaminated systems.

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.

Bioremediation of petroleum hydrocarbon by mixed bacteria culture of Pseudomonas aeruginosa and Brevibacterium sp.

The intention of this research is to overcome pollution by petroleum using bioremediation method with the help of hydrocarbonoclastic bacteria. The first step in this research was to characterize petroleum as pollutants and cultivate mixed culture bacteria, i.e. Pseudomonas aeruginosa and Brevibacterium sp. The second step was degradation test with growth medium of SMSS (Stone Mineral Salt Solution) with variations pH and concentration. It was conducted in a 300 ml Erlenmeyer series with composition of 80% media, 5% petroleum, and 10% bacteria placed in an incubator shaker with a rotation speed of 200 rpm for 7 days. Based on the results from degradation test with growth medium of SMSS, obtained results that TPH (Total Petroleum Hydrocarbon) degradation efficiency is higher at a pH of 8 that is equal to 28.47%. In the variation of concentration, the highest degradation efficiency occurs at concentration of 20% oil which is reduced oil viscosity up to 22.00%. This research proves that Pseudomonas aeruginosa and Brevibacterium sp. can degrade hydrocarbon composition in petroleum with an efficiency of up to 20%.

Removal of crude oil by Thiobacillus sp. and Clostridium sp. at various temperatures and concentration of pollutant in liquid media

The activities of the petroleum mining industry in Indonesia have caused many problems by producing hazardous waste pollution that would produce dangers for plants, animals or human lives. One technique to recover environmental situation is through land farming technique. The purpose of this study is to overcome crude oil pollution in the environment by using biotechnology method through the process of enzymatic bioremediation. The parameters discussed to determine the optimal environmental conditions that provide the highest efficiency for Total Petroleum Hydrocarbon (TPH) degradation processes such as temperature with a variation of 25 – 45°C then the concentration of pollutants with a variation of 5% – 20%, and the contact time carried out in solid media with variations amounting to 3 – 21 days. After conducting research, research that produces the bacterium Thiobacillus sp. and Clostridium sp. under optimal conditions at 35°C with a pollutant concentration of 10% and a contact time of 14 days. Thus, it can be concluded that the bacterium Thiobacillus sp. and Clostridium sp. can set aside hydrocarbon compounds with a removal efficiency of 65%. So, this research needs to be done to study other physical parameters.

Effect of consortium bioaugmentation and biostimulation on remediation efficiency and bacterial diversity of diesel-contaminated aged soil.

This study aimed to evaluate the effects of consortium bioaugmentation (CB) and various biostimulation options on the remediation efficiency and bacterial diversity of diesel-contaminated aged soil. The bacterial consortium was prepared using strains D-46, D-99, D134-1, MSM-2-10-13, and Oil-4, isolated from oil-contaminated soil. The effects of CB and biostimulation were evaluated in various soil microcosms: CT (water), T1 (CB only), T2 (CB + NH4NO3 and KH2PO4, nutrients), T3 (CB + activated charcoal, AC), T4 (CB + nutrients + AC), T5 (AC + water), T6 (CB + nutrients + zero-valent iron nanoparticles, nZVI), T7 (CB + nutrients + AC + nZVI), T8 (CB + activated peroxidase, oxidant), T9 (AC + nZVI), and T10 (CB + nZVI + AC + oxidant). Preliminary evaluation of the bacterial consortium revealed 81.9% diesel degradation in liquid media. After 60days of treatment, T6 demonstrated the highest total petroleum hydrocarbon (TPH) degradation (99.0%), followed by T1 (97.4%), T2 (97.9%), T4 (96.0%), T7 (96.0%), T8 (94.8%), T3 (93.6%), and T10 (86.2%). The lowest TPH degradation was found in T5 (24.2%), T9 (17.2%), and CT (11.7%). Application of CB and biostimulation to the soil microcosms decreased bacterial diversity, leading to selective enrichment of bacterial communities. T2, T6, and T10 contained Firmicutes (50.06%), Proteobacteria (64.69%), and Actinobacteria (54.36%) as the predominant phyla, respectively. The initial soil exhibited the lowest metabolic activity, which improved after treatment. The study results indicated that biostimulation alone is inadequate for remediation of contaminated soil that lacks indigenous oil degraders, suggesting the need for a holistic approach that includes both CB and biostimulation. Graphical Abstract.

Biochar and compost-based phytoremediation of crude oil contaminated soil

Objectives: To study the effect of compost and biochar on phytoremediation of crude oil-contaminated soil. Methods: An attempt was made to remediate crude oil contaminated soil, using the phytoremediation method. The soil was amended with biochar and compost. Initially, the pH, moisture content and C/N ratio of the soil and amendments were determined. A pot culture experiment was conducted to study the effect of the amendments on the degradation of the Total Petroleum Hydrocarbons (TPH) in the crude oil contaminated soil using the plant species nutgrass (Cyperus rotundus). To avoid seepage of water from the pots plastic pots were used. The initial concentration of TPH was found to be 17mg/kg soil. The experiment was conducted from January to March 2019. No microorganism was inoculated either to enhance the growth of the plant or degrade the hydrocarbon. The study was conducted with natural microflora. The pots were kept (open) under direct sunlight with 8 hours of photoperiodism. The plants were watered daily with tap water to maintain optimum moisture content. Once in 15 days, the soil samples collected from each treatment were analysed for pH, moisture content and C/N ratio. The TPH removal rate was determined for the 45th day and 60th day. Findings: The soil amended with compost (200 kg/soil) and biochar (50 kg/soil) enhanced the degradation of TPH by the plant species. The highest degradation percent of 62.2 and 77.1% was achieved on 45th and 60th day respectively in the treatment T5 (amended with biochar and compost). Further, there was an increase in shoot length (54.52 cm/plant), root biomass (0.74 g/plant) and shoot biomass (5.08g/plant) of the plants in the biochar and compost amended soil which was comparable with the results of the treatment T2 (Plants were grown in soil without crude oil contamination). Applications: Biochar and compost amendment improves the water holding capacity and nutrient status of the soil, thereby enhancing the growth of TPH degraders in soil. Hence, from the study, it is understood that biochar and compost could be used for phytoremediation of crude oil contaminated soils. Keywords: Amendments; degradation of TPH; nutgrass

Petroleum hydrocarbon-contaminated soil bioremediation assisted by isolated bacterial consortium and sophorolipid.

Pollution in soil by petroleum hydrocarbon has become a global environmental problem. The bioremediation of petroleum hydrocarbon-contaminated soil was enhanced with the combination of an isolated indigenous bacterial consortium and biosurfactant. The biodegradation efficiency of total petroleum hydrocarbon (TPH) was increased from 12.2% in the contaminated soil to 44.5% and 57.7% in isolated consortium and isolated consortium & 1.5g sophorolipid (SL)/kg dry soil, respectively. The half-life of TPH degradation process was decreased from 32.5d in the isolated consortium reactor to 20.4d in the isolated consortium & 1.5g SL/kg dry soil. The addition of biosurfactant into contaminated soils improved the TPH desorption from solid matrix to the aqueous solution and the subsequent solubilization, which ultimately improved the bioavailability of TPH in contaminated soils. Biosurfactant also served as carbon sources which contributed to the stimulation of cell growth and microbial activity and accelerated the biodegradation process via co-metabolism. The enzyme activities and quantities of functional genes were demonstrated to be incremented in SL reactors. The biosurfactant improved the TPH bioavailability, stimulated the microbial activities and participated in the co-metabolism. The combination of bioaugmentation and SL benefitted the bioremediation of petroleum hydrocarbon-contaminated soil.

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.

Insights into Bacterial Community Involved in Bioremediation of Aged Oil-Contaminated Soil in Arid Environment.

Soil contamination by hydrocarbons due to oil spills has become a global concern and it has more implications in oil producing regions. Biostimulation is considered as one of the promising remediation techniques that can be adopted to enhance the rate of degradation of crude oil. The soil microbial consortia play a critical role in governing the biodegradation of total petroleum hydrocarbons (TPHs), in particular polycyclic aromatic hydrocarbons (PAHs). In this study, the degradation pattern of TPHs and PAHs of Kuwait soil biopiles was measured at three-month intervals. Then, the microbial consortium associated with oil degradation at each interval was revealed through 16S rRNA based next generation sequencing. Rapid degradation of TPHs and most of the PAHs was noticed at the first 3 months of biostimulation with a degradation rate of pyrene significantly higher compared to other PAHs counterparts. The taxonomic profiling of individual stages of remediation revealed that, biostimulation of the investigated soil favored the growth of Proteobacteria, Alphaprotobacteria, Chloroflexi, Chlorobi, and Acidobacteria groups. These findings provide a key step towards the restoration of oil-contaminated lands in the arid environment.

Succession of microbial communities and synergetic effects during bioremediation of petroleum hydrocarbon-contaminated soil enhanced by chemical oxidation

Biotechnologies integrated with chemical techniques are promising in treating the soils contaminated by petroleum hydrocarbons. Experiments by applying the degrading consortium and the modified Fenton (MF) with the chelator sodium citrate simultaneously were carried out to investigate the effects of the MF reagents on the degradation of total petroleum hydrocarbons (TPHs), changes in enzyme activities and the succession of microbial communities at the 0, 20, 100 and 500 mmol/kg hydrogen peroxide concentration levels. The ratio between hydrogen peroxide, ferrous sulfate and sodium citrate in the MF reagents was 100:1:1. The results indicated that the degradation of TPHs conformed to first-order kinetics and MF treatments increased the total removal rates of TPHs (4.73–24.26%) and activated dehydrogenase and polyphenol oxidase activities. A shift in microbial communities from Proteobacteria to Bacteroidetes was observed during the enhanced bioremediation, and the predominant genus shifted from Pseudomonas with an average relative abundance (ARAs) of 76.61% at the beginning to Sphingobacterium with ARAs of 52.06% at the later stage. The MF reagents at the proper level could simplify the relationship among the community populations, alleviate their competition and strengthen their associations, which would optimize the removal efficiency.

Treatment of petroleum refinery sludge by petroleum degrading bacterium Stenotrophomonas pavanii IRB19 as an efficient novel technology

Petroleum hydrocarbons (PHCs) in petroleum refinery sludge (PRS) are the most adverse components because of their toxic nature, which are harmful to human health and the aquatic ecosystem. This study aimed to identify and characterize an indigenous bacterium isolated from PRS of Indian oil corporation ltd. (IOCL), Haldia, India, and evaluate its performance for biodegradation of total petroleum hydrocarbon (TPH) of PRS. The bacterium molecularly characterized as Stenotrophomonas sp. IRB19 by 16S rRNA sequencing and phylogenetic analysis. The strain IRB19 showed a significant ability to utilize four different oils (kerosene, diesel, petrol and hexadecane) in-vitro. IRB19 could able to degrade up to 65 ± 2.4% of TPH in 28 d of incubation. Solvent extraction study showed that PRS contain 180.57 ± 3.44 g kg−1 of TPH and maltene fraction composed of aliphatic, aromatics and polar components of 52 ± 4, 39 ± 2 and 9 ± 1%, respectively. The TPH degradation best fitted for the Gompertz model and followed the first-order kinetics having the rate constant (k) and half-life period (t 1/2) of 0.036 d−1 and 19 d, respectively. Results of this study verified the suitability of the novel strain IRB19 for the biodegradation of PHCs.

Bioremediation of oily sludge by solid complex bacterial agent with a combined two-step process

In the present research, a bioremediation process was developed using solid complex bacterial agents (SCBA) through a combined two-step biodegradation process. Four isolated strains showed high efficiency for the degradation of total petroleum hydrocarbons (TPH) and the reduction of COD of the oily sludge, at 96.6% and 92.6%, respectively. The mixed strains together with bran prepared in form of SCBA exhibited improved performance compared to individual strains, all of which had an optimal temperature of around 35 °C. The use of SCBA provided advantages over commonly used liquid media for storage and transportation. The two-step process, consisting of firstly biosurfactant-assisted oil recovery and secondly biodegradation of the remaining TPH with SCBA, demonstrated the capability for treating oily sludge with high TPH content (>10 wt%) and short process period (60 days). The large-scale (5 tons oily sludge) field test, achieving a TPH removal efficiency of 93.8% and COD reduction of 91.5%, respectively, confirmed the feasibility and superiority of the technology for industrial applications.