Total Petroleum Hydrocarbon Reduction Research Articles

Influence of Activated Carbon and Other Additives on Bioremediation Rate and Characteristics of Petroleum-Contaminated Soils

The main objective of this research was to study remediation of petroleum-contaminated soils after treating with granular activated carbon (AC) in combination with diatomite and a biopreparation (BP). Bioremediation rate and properties of petroleum-contaminated soils were used to explore associated mechanisms. Experiments were conducted under microfield conditions with three types of soils surficially contaminated with crude oil followed by weathering. Soil samples were amended with BP and two doses of AC (in combination or separately) or with diatomite alone (D) and mixed with AC (ACD). Natural attenuation decreased the concentration of total petroleum hydrocarbons (TPH) in the soils (initially 28–29 g kg−1) by 50% at 2 and 72% at 13 months. More efficient reduction of TPH (by 81% at 2 and 85% at 13 months) was achieved during the same period via in situ bioremediation by activating indigenous petroleum degraders, whereas the impact of BP alone was negligible. Soil amendment with the ACD mixture produced the best results; TPH content was reduced by 90% at 2 and 92% at 13 months, and soil phytotoxicity was low during most of the incubation period. Results demonstrated the potential of ACD as an adsorbent for accelerated bioremediation of petroleum-contaminated soils. Addition of the ACD mixture creates better conditions for degrading microorganisms and plant growth due to reversible adsorption of toxic petroleum components and metabolites, an increase in soil water-holding capacity, and total porosity, as well as a liming effect, increased plant resistance to abiotic stress in the presence of ACD, and better availability of compounds adsorbed to AC in the presence of diatomite.

Enhanced biodegradation of hydrocarbons in petroleum tank bottom oil sludge and characterization of biocatalysts and biosurfactants

Petroleum hydrocarbon removal from tank bottom oil sludge is a major issue due to its properties. Conventional physicochemical treatment techniques are less effective. Though the bioremediation is considered for the hydrocarbon removal from tank bottom oil sludge, the efficiency is low and time taking due to the low yield of biocatalysts and biosurfactants. The focal theme of the present investigation is to modify the process by introducing the intermittent inoculation for the enhanced biodegradation of hydrocarbons in the tank bottom oil sludge by maintaining a constant level of biocatalysts such as oxidoreductase, catalase, and lipase as well as biosurfactants. In addition, the heavy metal removal was also addressed. The microbial consortia comprising Shewanalla chilikensis, Bacillus firmus, and Halomonas hamiltonii was used for the biodegradation of oil sludge. One variable at a time approach was used for the optimum of culture conditions. The bacterial consortia degraded the oil sludge by producing biocatalysts such as lipase (80 U/ml), catalase (46 U/ml), oxidoreductase (68 U/ml) along with the production of lipoprotein biosurfactant (152 mg/g of oil sludge) constantly and achieved 96% reduction of total petroleum hydrocarbon. The crude enzymes were characterized by FT-IR and the biosurfactant was characterized by surface tension reduction, emulsification index, FT-IR, TLC, and SDS-PAGE. GC-MS and NMR also revealed that the hydrocarbons present in the oil sludge were effectively degraded by the microbial consortia. The ICP-OES result indicated that the microbial consortium is also effective in removing the heavy metals. Hence, bioremediation using the hydrocarbonoclastic microbial consortium can be considered as an environmentally friendly process for disposal of tank bottom oil sludge from petroleum oil refining industry.

Microbial degradation of total petroleum hydrocarbon in crude oil polluted soil ameliorated with agro-wastes

Microbial degradation of Total Petroleum Hydrocarbon (TPH) in crude oil polluted soil ameliorated with agro-wastes was assessed. Six kilogrammes of each composite soil samples collected from three points were weighed into 150 plastic buckets with drainage holes at the base. The soil samples were spiked with 300 ml of crude oil and treated with agricultural wastes (groundnut husk, maize cobs, cassava peels and empty fruit bunch of oil palm husks) in single and combined form. Experimental data for the total petroleum hydrocarbon content of the soils were collected every 30 days for 90 days. Statistical analysis was done using a three-way analysis of variance (3-Way ANOVA) and significant variations were checked using the least significant difference test at 5% probability level. The results showed that there were significant variations in the mean values between the different treatment groups. However, the combined amendments GnH14P + Mac14P, CasP14P + Mac14P and GnH14P + CasP14P at 10% treatment level had the lowest hydrocarbon contents in the soil with mean values of 197.04, 202.89 and 185.34 respectively. While at 90DAST GnH14P + Mac14P and GnH14P + EFBOP14P had reduced TPH in soil with mean values of 82.94 and 84.72 respectively. High percentage degradation rates was observed in soil amended with GnH14P, GnH14P + CasP14P and GnH14P + Mac14P with mean values of 90.85, 89.12 and 88.43% respectively. It was concluded that the combined treatment with groundnut husks enhances microbial proliferation in soil and produces a strong influence in the reduction of total petroleum hydrocarbons in soils.

Biostimulation and bioaugmentation of native microbial community accelerated bioremediation of oil refinery sludge

Scope for developing an engineered bioremediation strategy for the treatment of hydrocarbon-rich petroleum refinery waste was investigated through biostimulation and bioaugmentation approaches. Enhanced (46–55%) total petroleum hydrocarbon (TPH) attenuation was achieved through phosphate, nitrate or nitrate+phosphate amendment in the sludge with increased (upto 12%) abundance of fermentative, hydrocarbon degrading, sulfate-reducing, CO2-assimilating and methanogenic microorganisms (Bacillus, Coprothermobacter, Rhodobacter, Pseudomonas, Achromobacter, Desulfitobacter, Desulfosporosinus, T78, Methanobacterium, Methanosaeta, etc). Together with nutrients, bioaugmentation with biosurfactant producing and hydrocarbon utilizing indigenous Bacillus strains resulted in 57–75% TPH reduction. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis revealed enhanced gene allocation for transporters (0.45–3.07%), ABC transporters (0.38–2.07%), methane (0.16–1.06%), fatty acid (0.018–0.15%), nitrogen (0.07–0.17%), butanoate (0.06–0.35%), propanoate (0.004–0.26%) metabolism and some xenobiotics (0.007–0.13%) degradation. This study indicated that nutrient-induced community dynamics of native microorganisms and their metabolic interplay within oil refinery sludge could be a driving force behind accelerated bioremediation.

Phytoremediation of soil polluted with Iraqi crude oil using grass plant

Remediation technology is a promising technique that decreases pollutants like hydrocarbons from the environment. An experimental work was done at green house of University of Technology in order to study the effect of crude oil on the plant growth and to measure the decrement which happened on shoot height, germination rate and the reduction of total petroleum hydrocarbon (TPH), which resulted by this phytoremediation technique. The samples of soil were measured for TPH reduction and removal by Horiba model OCMA - 350. Five doses were used in this experiment (0 control, 10x103, 30 x103, 50 x103, 75 x103) (mg crude oil / kg soil) or (ppm). The greater efficiency was obtained in the treatment 50 x103 ppm seeded with cotton, in which cotton removed 50.66% of the primary TPHs from soil. Results showed that the employed vegetate species were promising and effective in reducing and removing TPHs from freshly polluted soil.

Application of Root Maceration of Common Weeds: T. diversifolia and S. jamaicensis for Phytoremediation of Ohaji Egbema Crude Oil Polluted Soils

This study examined the remediation of crude oil polluted soils obtained from Ohaji Egbema Imo State Nigeria using macerated roots of T. diversifolia (TD) and S. jamaicensis (SJ). The soil pH levels, PAHs (Polycyclic aromatic hydrocarbons) and TPH (Total petroleum hydrocarbons) contents, and catalase and peroxidase activities were evaluated. Thirty-two polyethene bags containing 300g of soil samples were divided into eight groups of quadruplicates. Group 1 were the unpolluted soil samples (USS), group 2; polluted soil samples (PSS) without remediation, group 3; PSS containing 250g of TD, group 4; PSS containing 500g of TD, group 5; PSS containing 250 g of SJ, group 6; PSS containing 500g of SJ, group 7; PSS containing 250g of the mixture of TD and SJ (1:1) and group 8; PSS containing 500g of the mixture of TD and SJ (1:1). At all experimental periods, the pH of the PSS without remediation was significantly lower than the USS. The 500 g TD completely normalized the altered pH of the PSS on the 4th week, comparable to the results of the 12th week. The PAH (Polycyclic aromatic hydrocarbons) levels in the group 5 and 7 on the 1st day were not significantly different from the PAH of the group 2. Group 3, 4, 7, and 8 produced the best PAH lowering effects on the polluted soils on the 8th week, which compared to the results of the 12th week. At all experimental periods, 500g of TD provided the most effective for TPH reduction of the polluted soils. Results for the enzyme activities showed a significantly decreased (p < 0.05) catalase and peroxidase levels of the polluted soils when compared to the USS. Both the 1st day and 1st week recorded similar catalase activities in all groups except group 5, while group 4-8 recorded significantly increased catalase activities from the 4 - 12th week. For the 1st day, 1st week, and 4th week, increasing the amount of the plants from 250g - 500g had no effect on the peroxidase levels of the soils, while a quantity dependent significant increase in peroxidase levels was observed only for group 7 and 8 on the 8th and 12th weeks. The 500g TD produced the most significant restorative effect on the polluted soils. This study has shown the extensive remediation produced by TD on crude oil polluted soils of Ohaji Egbema.

Evaluating the use of spiny pigweed (&lt;i&gt;Amaranthus spinosus&lt;/i&gt;) and water leaf (&lt;i&gt;Talinum triangulare&lt;/i&gt;) for bioremediation of crude oil polluted soil in Ikarama Community in Bayelsa State Nigeria

The potential soil amending impact of various concentrations of macerated roots of Amaranthus spinosus and Talinum triangulare singly and in combination on crude oil polluted soil of Ikarama community of Yenagoa in Bayelsa State Nigeria was investigated using gas chromatography technique for twelve weeks. The polluted soil was bagged in seven groups with the addition of 250g of Amaranthus spinosus root, 500g of Amaranthus spinosus root, 250g of Talinum triangulare root, 500g of Talinum triangulare root, 250g of combined roots of Amaranthus spinosus and Talinum Triangulare, 500g of combined roots of Amaranthus spinosus and Talinum Triangulare and labelled as follows Ga, Gb, Wa, Wb, GWa and GWb respectively; and a polluted and not amended bag which served as control. Each bag contained 1000g of polluted soil. The Total Petroleum Hydrocarbon (TPH), Polycyclic Aromatic Hydrocarbon (PAH), pH and enzyme concentration were analysed at intervals of four weeks for twelve weeks. The result showed that TPH reduction in the impacted soil varied between 29.5% for Ga and 1.79% for Wa after week 4.The results also showed that PAH reduction varied between 53% for Gb and 14.2% in GWa at week 12 (p&lt;0.05). The results suggested that the roots of the plants Talinum triangulare and Amaranthus spinosus are best used singularly and not in combination in the bioremediation of TPH and PAHs.Keywords: Amaranthus spinosus, Bioremediation, crude oil, polycyclic aromatic hydrocarbon, Talinum triangulare, Total petroleum hydrocarbon

Assessment of hydrocarbon degradation potentials in a plant–microbe interaction system with oil sludge contamination: A sustainable solution

ABSTRACTA pot culture experiment was conducted for 90 days for the evaluation of oil and total petroleum hydrocarbon (TPH) degradation in vegetated and non-vegetated treatments of real-field oil-sludge-contaminated soil. Five different treatments include (T1) control, 2% oil-sludge-contaminated soil; (T2), augmentation of microbial consortium; (T3), Vertiveria zizanioides; (T4), bio-augmentation along with V. zizanioides; and (T5), bio-augmentation with V. zizanioides and bulking agent. During the study, oil reduction, TPH, and degradation of its fractions were determined. Physico-chemical and microbiological parameters of soil were also monitored simultaneously. At the end of the experimental period, oil content (85%) was reduced maximally in bio-augmented rhizospheric treatments (T4 and T5) as compared to control (27%). TPH reduction was observed to be 88 and 89% in bio-augmented rhizospheric soil (T4 and T5 treatments), whereas in non-rhizospheric and control (T2 and T1), TPH reduction was 78 and 37%, respectively. Degradation of aromatic fraction after 90 days in bio-augmented rhizosphere of treatments T4 and T5 was found to 91 and 92%, respectively. In microbial (T2) and Vertiveria treatments (T3), degradation of aromatic fraction was 83 and 68%, respectively. A threefold increase in soil dehydrogenase activity and noticeable changes in organic carbon content and water-holding capacity were also observed which indicated maximum degradation of oil and its fractions in combined treatment of plants and microbes. It is concluded that the plant–microbe soil system helps to restore soil quality and can be used as an effective tool for the remediation of oil-sludge-contaminated sites.

Optimization of combined in-vessel composting process and chemical oxidation for remediation of bottom sludge of crude oil storage tanks

ABSTRACTIn this research, removal of petroleum hydrocarbons from oily sludge of crude oil storage tanks was investigated under the optimized conditions of in-vessel composting process and chemical oxidation with H2O2 and Fenton. After determining the optimum conditions, the sludge was pre-treated with the optimum state of the oxidation process. Then, the determined optimum ratios of the sludge to immature compost were composted at a C:N:P ratio of 100:5:1 and moisture content of 55% for a period of 10 weeks. Finally, both pre-treated and composted mixtures were again oxidized with the optimum conditions of the oxidants. Results showed that total petroleum hydrocarbons (TPH) removal of the 1:8 and 1:10 composting reactors which were pre-treated with H2O2 were 88.34% and 90.4%, respectively. In addition, reduction of TPH in 1:8 and 1:10 composting reactors which were pre-treated with Fenton were 83.90% and 84.40%, respectively. Without applying the pre-treatment step, the composting reactors had a removal rate of about 80%. Therefore, pre-treatment of the reactors increased the TPH removal. However, post-oxidation of both pre-treated and composted mixtures reduced only 13–16% of TPH. Based on the results, remarkable overall removal of TPH (about 99%) was achieved by using chemical oxidation and subsequent composting process. The study showed that chemical oxidation with H2O2 followed by in-vessel composting is a viable choice for the remediation of the sludge.

Total petroleum hydrocarbon degradation in contaminated soil as affected by plants growth and biochar

This study was conducted to investigate the effect of barley and oat plants and poultry manure biochar on total petroleum hydrocarbons (TPHs) degradation and microbial respiration at 4, 6 and 8% TPH levels in soil. Results showed that with increasing TPH levels, plants growth and TPHs degradation significantly reduced; however, the presence of plants in contaminated soil and application of biochar significantly increased degradation of TPHs and microbial respiration rate. TPHs reduction percentage in soils cultivated with barley and oat were about 1.02 and 0.75 times higher than unplanted soil. Microbial respiration rate in soil cultivated with barley and oat increased about 67 and 34.5% compared to unplanted treatment. TPHs reduction percentage and average of microbial respiration rate in biochar-treated soil significantly increased by 21.76 and 37.73% for barley and 20.36 and 45.18% for oat plant compared to non-biochar treatments, respectively. Barley and oat appear to be suitable for degradation of TPHs, and biochar is useful amendment for enhancing TPHs degradation in this soil.

Optimization, kinetics, physicochemical and ecotoxicity studies of Fenton oxidative remediation of hydrocarbons contaminated groundwater

Fenton oxidation remediation of hydrocarbons contaminated groundwater was investigated for efficiency and effectiveness. 10% pollution was simulated in the laboratory by contaminating groundwater samples with diesel and domestic purpose kerosene (DPK) in two different experimental set ups. Optimum conditions of concentrations of the treatment solutions and pH were established: 300mg/L (FeSO4), 150,000mg/L (H2O2) and pH = 3 for the kerosene contaminant; 100mg/L (FeSO4), 300,000mg/L (H2O2) and pH = 3 for the diesel contaminant. The results from kinetics study show that the remediation process is pseudo-first order reaction with a rate constant of 8.07×104mgL−1hr−1 and 3.13×104mgL−1hr−1 for the diesel and kerosene contaminants in that order with 95.32% and 79.25% reduction in chemical oxygen demand (COD) for diesel and kerosene contaminated samples at the end of the remediation process respectively indicated that remediation have occurred significantly. Percent reduction in Total Petroleum Hydrocarbon (TPH) as kerosene was 89.84% and that of the diesel contaminant as 91.87% after 6hours of remediation. The general pollution index (GPI) for the hydrocarbons contaminated samples was in the range of 6.70–7.52 against the background value of 4.39 for the control groundwater sample. After treatment the GPI had dropped to 4.13–4.43 which depicts remarkable remediation although the samples remained impaired. Therefore there is the need of post-treatments to make the groundwater fit for domestic and agricultural uses. The application of the Fenton oxidative process is found to be very efficient, effective and rapid in reducing total petroleum hydrocarbon as kerosene and diesel as target contaminants.

Influence of a Dispersant on the Types and Growth of Microbial Hydrocarbon Degraders in a Crude Oil-contaminated Medium.

Background:Dispersants are first order response strategies for oil spill cleanup in an aquatic environment. However, their effects on the biodegradation capacity of indigenous hydrocarbon-degrading microorganisms are little known.Objectives:The influence of a dispersant (DS/TT/066) on the type(s) and growth of hydrocarbon-degrading bacteria (HDB) and hydrocarbon-degrading fungi (HDF) in a crude oil-contaminated medium (water) was investigated in the laboratory for 28 days.Methods:The experiment was set up in duplicates with the first set containing Forcados light crude oil (FLCO) alone in water while the other was a mixture of FLCO and DS/TT/066 (ratio 9:1 v/v). Identification and enumeration of HDB and HDF were conducted according to standard methods. Total petroleum hydrocarbons (TPH) in the test media was analyzed using a gas chromatography/flame ionization detector.Results:The results showed that HDB identified in the FLCO alone included Pseudomonas aeruginosa (day 0), Proteus vulgaris (day 14), P. aeruginosa and Kliebsiella pneumoniae (day 28). However, in the mixture, Escherichia coli was identified on day 14 in addition to the other species observed in FLCO alone. HDF identified in FLCO alone were Candida krusei and Candida albicans (days 0 and 14), Trichosporon cutaneum and C. albicans (day 28). In the mixture, HDF identified were C. albicans (day 0), C. albicans and Aspergillus spp. (days 14 and 28)″ Furthermore, the mixture enhanced the growth of HDBF (average counts: 32.5 × 107 and 225 × 106 cfu/mL) compared to FLCO alone (17.5 × 107 and 17.5 × 106 cfu/mL) by day 14 respectively. Total petroleum hydrocarbon reduction was highest (85%) in the mixture compared to 5% in FLCO alone by day 14.Conclusions:The study demonstrated the biodegradation efficiency of E. coli, P. vulgaris (bacteria), C. albicans and Aspergillus spp. (fungi) in a crude oil-contaminated aquatic environment in conjunction with dispersant use. Further studies in the field are recommended in order to explore their potential for rapid and large scale crude oil clean-up operations.

HORMESIS PHENOMENA OF SOME PARAMETER ASPECT IN USAGE OF WATER LETTUCE (Pistia stratiotes L.) FOR PHYTOREMEDIATION PROCESS OF PETROLEUM LIQUID WASTE

The research about potential test of water lettuce (Pistia stratiotes) in order of phytoremediation of petroleum liquid waste had been done during June untill December 2012 at Microbiology Laboratory, Department of Biology, Faculty of Science, The University of Sriwijaya, Indonesia. Completely Randomized Design was used in the experiment while the concentration of liquid waste as treatment were: 0, 15, 30, 45, 60 and 75 %. Each treatment were replicated 4 times. Three parameter was measured; Total Petroleum Hydrocarbons (TPH) reduction percentage, efficiency of phytoremediation and number of tillers. Regression analisys were used for the data and two of parameters show the hormesis phenomena, were; efficency of phytoremediation and number of tillers. The highest peak effect of treatment for efficiency of phytoremediation and number of tillers was on 45 %. TPH reduction percentage was the only one parameter that shows linier regression Keywords hormesis, Pistia stratiotes, TPH, phytoremediation, tiller

Crude oil degradation potential of bacteria isolated from oil-polluted soil and animal wastes in soil amended with animal wastes

The influence of animal wastes on crude oil degradation potential of strains of Proteus vulgaris and Bacillus subtilis isolated from animal wastes (poultry and pig droppings) and petroleum-polluted soil was compared in laboratory studies. Both bacterial strains were selected for high crude oil degradation ability after screening many isolates by the 2,6-dichlorophenol indophenol method. Analyses by gas chromatography (GC) showed that degradation of crude oil was markedly enhanced (88.3–97.3% vs 72.1–78.8%) in soil amended with animal wastes as indicated by the reduction of total petroleum hydrocarbon (TPH). TPH reduction by animal waste bacterial strains in animal waste-amended soil was more than the reduction by strains from soil contaminated with petroleum (P < 0.001). The greatest reduction of TPH (96.6–97.3% vs 80.4–95.9%) was by poultry waste strains and it occurred in soil amended with poultry waste. GC analyses of n-alkanes showed that although shorter chains were preferentially degraded [32.0–78.5% (C8–23) vs 6.3–18.5% (C24–36)] in normal soil, biodegradation of longer chains increased to 38.4–46.3% in animal waste-amended soil inoculated with the same animal wastes’ strains. The results indicate that these animal waste strains may be of potential application for bioremediation of oil-polluted soil in the presence of the wastes from where they were isolated.

Earthworm-assisted bioremediation of petroleum hydrocarbon–contaminated soils from motorcar mechanic workshops in Ibadan, Oyo State, southwestern Nigeria

ABSTRACTEnhanced microbial bioremediation of petroleum hydrocarbon–contaminated (PHC) soils with the earthworm Alma millisoni and the bacterium Bacillus spp. was conducted. The petroleum-contaminated topsoils (PCTS) (0–15 cm) collected from motorcar mechanic workshops were thoroughly mixed, sieved, and air dried for 7 days. The pH, water holding capacity (WHC), total nitrogen (N), organic carbon (OC), heavy metal (HM), and bacteriological analysis of the soil samples were evaluated. The indigenous bacterial isolates were subjected to 1%, 5%, and 50% of spent engine oil (SEO), incubated for 7 days at 37°C, and the isolate with the highest tolerance pattern was used for the remediation. Out of four indigenous bacteria isolated, Bacillus spp. had the highest tolerance to SEO. Preliminary exposure assessments of A. millisoni to PHC soils (100%, 60%, 50%, and 40% PHC) were carried out using 48-h avoidance response, coiling exhibition, swollen clitelium, 14-day survival tests, and antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPx). Subsequently, four treatments of 1 kg soil mixed with 100%, 75%, 50%, and 0% PCTS were designed and spiked with 20 g of dried cow dung. Each of the treatments consisted of four setups, viz., A. millisoni alone, A. millisoni and Bacillus spp., Bacillus spp. alone, and control. The bacterial counts, total petroleum hydrocarbon (TPH), total and bioavailable HM, and total OC and N of the soils were evaluated every 7 days for 35 days. Significant increases in the activities of CAT, SOD, GPx, and GST compared with control were recorded in A. millisoni exposed to the various treatments. Treatment with combined A. millisoni and Bacillus spp. resulted in significant (p < .05) reduction in TPH, reduction in total and bioavailable heavy metals, and increased total OC and N of the soil compared with other treatments. The percentage reduction in TPH and heavy metals with concomitant increase in total OC and total N recorded in the 50% PHC soils followed the order A. millisoni and Bacillus spp. > A. millisoni alone > Bacillus spp. alone. Hence, enhanced bioremediation using A. millisoni and Bacillus spp. may be a good biocatalyst in the remediation of petroleum hydrocarbon–contaminated soils.

Biostimulation of Indigenous Microbial Community for Bioremediation of Petroleum Refinery Sludge.

Nutrient deficiency severely impairs the catabolic activity of indigenous microorganisms in hydrocarbon rich environments (HREs) and limits the rate of intrinsic bioremediation. The present study aimed to characterize the microbial community in refinery waste and evaluate the scope for biostimulation based in situ bioremediation. Samples recovered from the wastewater lagoon of Guwahati refinery revealed a hydrocarbon enriched [high total petroleum hydrocarbon (TPH)], oxygen-, moisture-limited, reducing environment. Intrinsic biodegradation ability of the indigenous microorganisms was enhanced significantly (>80% reduction in TPH by 90 days) with nitrate amendment. Preferred utilization of both higher- (>C30) and middle- chain (C20-30) length hydrocarbons were evident from GC-MS analysis. Denaturing gradient gel electrophoresis and community level physiological profiling analyses indicated distinct shift in community’s composition and metabolic abilities following nitrogen (N) amendment. High throughput deep sequencing of 16S rRNA gene showed that the native community was mainly composed of hydrocarbon degrading, syntrophic, methanogenic, nitrate/iron/sulfur reducing facultative anaerobic bacteria and archaebacteria, affiliated to γ- and δ-Proteobacteria and Euryarchaeota respectively. Genes for aerobic and anaerobic alkane metabolism (alkB and bssA), methanogenesis (mcrA), denitrification (nirS and narG) and N2 fixation (nifH) were detected. Concomitant to hydrocarbon degradation, lowering of dissolve O2 and increase in oxidation-reduction potential (ORP) marked with an enrichment of N2 fixing, nitrate reducing aerobic/facultative anaerobic members [e.g., Azovibrio, Pseudoxanthomonas and Comamonadaceae members] was evident in N amended microcosm. This study highlighted that indigenous community of refinery sludge was intrinsically diverse, yet appreciable rate of in situ bioremediation could be achieved by supplying adequate N sources.

Insights into the biodegradation of weathered hydrocarbons in contaminated soils by bioaugmentation and nutrient stimulation

The potential for biotransformation of weathered hydrocarbon residues in soils collected from two commercial oil refinery sites (Soil A and B) was studied in microcosm experiments. Soil A has previously been subjected to on-site bioremediation and it was believed that no further degradation was possible while soil B has not been subjected to any treatment. A number of amendment strategies including bioaugmentation with hydrocarbon degrader, biostimulation with nutrients and soil grinding, were applied to the microcosms as putative biodegradation improvement strategies. The hydrocarbon concentrations in each amendment group were monitored throughout 112 days incubation. Microcosms treated with biostimulation (BS) and biostimulation/bioaugmentation (BS + BA) showed the most significant reductions in the aliphatic and aromatic hydrocarbon fractions. However, soil grinding was shown to reduce the effectiveness of a nutrient treatment on the extent of biotransformation by up to 25% and 20% for the aliphatic and aromatic hydrocarbon fractions, respectively. This is likely due to the disruption to the indigenous microbial community in the soil caused by grinding. Further, ecotoxicological responses (mustard seed germination and Microtox assays) showed that a reduction of total petroleum hydrocarbon (TPH) concentration in soil was not directly correlable to reduction in toxicity; thus monitoring TPH alone is not sufficient for assessing the environmental risk of a contaminated site after remediation.

Treatment of Heavy, Long-Chain Petroleum-Hydrocarbon Impacted Soils Using Chemical Oxidation

AbstractChemical oxidation is a promising approach for in situ or ex situ treatment of heavy, long-chain (C12−C40) petroleum-hydrocarbon impacted soils. Aqueous chemical oxidation treatments (sodium percarbonate, hydrogen peroxide, sodium persulfate, chlorine dioxide, sodium permanganate, and ozone) using two oxidant concentrations were tested in batch tests on soils containing C12–C40 total petroleum hydrocarbon (TPH) concentrations of 1.6 and 2.0% weight/weight (w/w) resulting in TPH reductions from 20 to 90%. Gas chromatography with flame ionization detector (GC-FID) chromatograms for hydrocarbons were obtained and presented as chain-length fractions. Sodium percarbonate and hydrogen peroxide achieved the highest TPH reduction. There was little difference between 1 and 10% weight/volume (w/v) for all oxidant doses on TPH removal. Soluble organics in the liquid supernatants after oxidation of the TPH-containing soils were characterized by TPH analysis and excitation-emission matrix fluorescence spectros...

Stabilisation/solidification and bioaugmentation treatment of petroleum drill cuttings

Petroleum drill cuttings are usually treated by techniques suitable for particular contaminant groups. The significance of this study consists in the development of a treatment technology that can simultaneously handle the hydrocarbon and metal constituents of drill cuttings. Bioaugmentation is combined with stabilisation/solidification (S/S), within S/S monoliths and in granulated S/S monoliths. Portland cement was used for S/S treatment at 30% binder dosage. Bioaugmentation treatment involved two bacterial densities of a mixed culture bio-preparation. The effects of inclusion of compost, fertiliser and activated carbon were also evaluated. After 28 days, the combined S/S and bioaugmentation treatments recorded up to 15% higher total petroleum hydrocarbon (TPH) loss than control S/S treatment without bioaugmentation. Embedding fertiliser, activated carbon and higher bacterial density within S/S monoliths resulted in the highest (99%) TPH reduction but higher concentrations of metals. The addition of compost and lower bacterial density to granulated S/S monoliths led to similar (98%) TPH degradation and lower amounts of metals. The results suggest that with better mixture optimisation, combining S/S and bioaugmentation could engender more sustainable treatment of drill cuttings.

Hydraulic fracturing wastewater treatment by coagulation-adsorption for removal of organic compounds and turbidity

Waters produced from fracturing operations in the oil and gas industry are a complex mixture of fracturing fluids and formation water. Closing the water cycle loop in this industry depends on the effective reuse of these wastewaters, and therefore treatment. This study investigated the application of chemical coagulants and powdered activated carbon (PAC) to reduce turbidity, dissolved organic carbon (DOC), total petroleum hydrocarbons (TPH), and polyethylene glycols (PEGs) in four hydraulic fracturing wastewaters. Jar tests were performed to evaluate both the PAC and coagulants. Treatment goals were operationally defined targeting 90% reduction of turbidity, PEGs, and TPH. PAC was found to be effective at removing both PEGs and TPH from the wastewaters, but would not settle without the addition of a coagulant. Ferric chloride achieved a 90% reduction in turbidity at a lower dose than aluminum chlorohydrate, in the presence and absence of PAC. The optimized coagulant dose by itself had little to no effect upon concentrations of DOC and PEGs, while greater than 80% removal of TPH, a minor component of DOC, was observed in three of the waters. PAC at 1000mgL−1 achieved greater than 80% reductions of the total ion chromatogram, while DOC removals were from 9.5 to 48.3%. These results suggest that coagulation with ferric chloride at doses as low as 5mgL−1 is an effective process for turbidity and TPH reduction in hydraulic fracturing wastewaters, and when coupled with PAC can also remove DOC and targeted organic contaminants such as PEGs.