Total Petroleum Hydrocarbon Removal Efficiency Research Articles

Soil microbial community and association network shift induced by several tall fescue cultivars during the phytoremediation of a petroleum hydrocarbon-contaminated soil

Biodegradation of soil contaminants may be promoted near plant roots due to the “rhizosphere effect” which may enhance microbial growth and activity. However, the effects of different plant cultivars within a single species on degradation remains unclear. Here, we evaluated the removal of soil total petroleum hydrocarbons (TPHs) by ten different cultivars of tall fescue grass (Festuca arundinacea L.) and their associated rhizosphere microbiomes. TPH removal efficiency across the ten different cultivars was not significantly correlated with plant biomass. Rhizing Star and Greenbrooks cultivars showed the maximum (76.6%) and minimum (62.2%) TPH removal efficiencies, respectively, after 120 days. Significant differences were observed between these two cultivars in the composition of rhizosphere bacterial and fungal communities, especially during the early stages (day 30) of remediation but the differences decreased later (day 90). Putative petroleum-degrading bacterial and fungal guilds were enriched in the presence of tall fescue. Moreover, the complexity of microbial networks declined in treatments with higher TPH removal efficiency. The relative abundances of saprotrophic fungi and putative genes alkB and C12O in bacetria involved in petroleum degradation increased, especially in the presence of Rhizing Star cultivar, and this was consistent with the TPH removal efficiency results. These results indicate the potential of tall fescue grass cultivars and their associated rhizosphere microbiomes to phytoremediate petroleum hydrocarbon-contaminated soils.

Remediation of weathered diesel-oil contaminated soils using biopile systems: An amendment selection and pilot-scale study

Weathered diesel oil (WDO) has less biodegradable and volatile characteristics, and its bioremediation could be a challenge. In this study, the effectiveness of enhanced bioremediation via biopile processes for the cleanup of WDO-contaminated soils was evaluated. Six biopiles were constructed and operated with the following six different amendments addition: red bran (12 kg), water-soluble fertilizer (20 L/week), highly oxygenated water (20 L/d, dissolved oxygen = 25 mg/L), petroleum hydrocarbon-degrading bacterial culture (20 L/week), mixture of the above amendments, and natural attenuation (no amendment). Each biopile contained 5 m3 [2.5 m (L) × 2 m (W) × 1 m (H)] of WDO-contaminated soils [initial total petroleum hydrocarbon (TPH) concentrations = 3015 to 3785 mg/kg]. Soils were mixed with amendments and tilled for air supplement twice a week with soil moisture around 25%. Metagenomics analyses were applied to determine the microbial biodiversity and strains responsible for hydrocarbon biodegradation. Results show that the biopile system with mixed supplements (mixture group) had the highest TPH removal efficiency (79% of TPH removal) followed by red bran addition group with a removal efficiency of approximately 73% during the 42-day operation. The first-order TPH decay rates in mixture and red bran biopiles were around 3.2 × 10−2 1/d, which was 4.8 times higher than that obtained from natural attenuation biopile. Biopiles with red bran and mixture supplements contained carbon substrates and nutrients, which could effectively activate microbial activities and accelerate the TPH biodegradation. High carbon number compounds (C > 20) in WDO could be biodegraded within 24 days in the biopile with mixed amendments. Results from metagenomics study indicate that Sphingomonas and Pseudomonas might cause removal of heavy components (C24–30) and light components of petroleum hydrocarbons (C10–16), respectively.

Effectiveness of a bio-catalytic agent used in the bioremediation of crude oil-polluted seawater

Oil spillage contamination has been one of the most common and challenging problems in marine ecosystems over the years due to frequent petroleum exploitation, washing, and transportation activities. The use of nature-derived surfactants has become an attractive approach to restore the sites affected by oil spillage. Several studies have demonstrated that nutrient addition is an efficient strategy to enhance oil biodegradation since microorganisms can use petroleum hydrocarbons as their carbon and energy source, thus favoring and increasing the hydrocarbons degradation rate. This study aimed to assess the effectiveness of a commercial bio-catalytic agent used in the biological remediation of crude oil-contaminated sites through the qualitative analysis of its properties. The tests applied to this bio-catalyst showed excellent results. For instance, the emulsification (E24) and critical micellar concentration (CMC) assays displayed average values of 74.47% and 40 mg L−1, respectively. A significant reduction of Chemical Oxygen Demand (COD), turbidity, and Total Petroleum Hydrocarbon Content (TPHC) were observed in all the samples with bio-catalytic agent solution and aeration system. The best water quality was achieved by the sample with the highest concentration (10000 ppm) of bio-catalytic agent solution. It displayed a Total Petroleum Hydrocarbon removal efficiency (RTPH) of 81.537% after 30 days of the remediation time.

Development of a low-temperature thermal treatment process for the production of plant-growable media using petroleum-impacted dredged sediment

In this study, we investigate the potential of low-temperature thermal treatment to treat petroleum-impacted sediments to produce plant-growable media. The thermal treatment posed a marginal or moderate effect (i.e., 6–47% change) on most of the sediment physicochemical properties, including organic carbon, nutrient contents, and cation exchange capacity, while exhibiting a total petroleum hydrocarbon removal efficiency of 93%. The treatment reduced the bioavailability of heavy metals in the sediment, which was attributed to enhanced physical and/or chemical barriers against heavy metal leaching by sediment particle aggregation and carbonaceous matter formation. Because the oxidation of sediment constituents generated new plant stressors, water-soluble organics and sulfate salts, the thermal treatment by itself was insufficient to produce a medium favorable for the germination and growth of barley. These newly generated stressors were easily removed by water washing post-treatment to yield a final product that showed excellent performance in supporting barley germination and growth. This study demonstrates the benefit of low-temperature thermal treatment to simultaneously achieve control over source-originated contaminants and preserve the ecological value of the dredged sediments. This study also identifies plant stressors that were generated during the treatment, and describes an effective control strategy against them.

Evaluation of rhizoremediation and methane emission in diesel-contaminated soil cultivated with tall fescue (Festuca arundinacea)

Rhizoremediation, CH4 emission, and bacterial community dynamics were evaluated in diesel-contaminated soil cultivated with tall fescue via a pot experiment. At the beginning of the experiment, total petroleum hydrocarbons (TPHs) removal efficiency was 30.2% in tall fescue-cultivated soil, which was significantly higher than that of unplanted soil (19.4%). However, when compost was added as a soil amendment, TPHs removal efficiency increased to 39.2% in tall fescue-cultivated soil. Interestingly, potential CH4 emissions were more affected by the initial diesel concentration than by compost addition or tall fescue planting. Specifically, the potential CH4 emission was approximately 3.8 times higher in the treatment with the highest initial diesel concentration (T-WC38) than that of the treatment with the lowest initial diesel concentration (T-WC5). Functional gene analysis revealed that TPHs removal had a linear correlation with the alkB/16S gene ratio, whereas potential CH4 emission had a linear correlation with pmoA gene copy numbers. Initial diesel concentrations in soil also affected bacterial community structures and the genera Rhizobium, Halothiobacillus, and Geobacter were found to be positively linked to diesel-contaminated soil rhizoremediation. Therefore, this study provides useful insights into the development of strategies to enhance rhizoremediation efficiency and CH4 emission mitigation in diesel-contaminated soils.

Bioremediation of petroleum-contaminated soil by semi-aerobic aged refuse biofilter: Optimization and mechanism

Petroleum-contaminated soil (PCS) is a global environmental issue. An effective remediation technique is urgently needed to address this problem. This study applied a semi-aerobic aged refuse biofilter (SAARB) to the decontamination and remediation of PCS. The effects of petroleum content, surfactant content, and water content on oil removal efficiency were studied, and the operation conditions were optimized using the response surface method. Results showed that contents of petroleum and water that were too high or too low depressed total petroleum hydrocarbon (TPH) removal. The presence of surfactant markedly reduced the TPH removal efficiency. The optimal operation conditions were the ratio of aged refuse to PCS = 1.6; water content = 41%; and petroleum content = 3.8%. The TPH removal efficiencies under optimized conditions and during a confirmatory experiment were 59.89% and 51.38%, respectively. PCS contained an abundance of polycyclic aromatic hydrocarbons and macro molecular alkanes, and these organic compounds were considerably removed by SAARB treatment. The microbial community exhibited a marked change at both phylum level and genus level after 3 months of remediation in the PCS. At the genus level, norank_f_SS1–B-06-26 became the most dominant; further isolation and verification experiments for its ability to degrade petroleum are needed. In addition, the abundance of norank_o_Saccharimonadales, Aquabacterium, Hydrogenophaga, and norank_f_Saccharimonadaceae, which can degrade hydrocarbons, also increased. This study provides a theoretical reference for SAARB application in the remediation of PCS.

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.

Remediation of oil-based drilling waste using the electrokinetic-Fenton method

The large amount of residues and pollutants left over from the drilling industry could cause irreparable damage by entering the human and animal food chain. Therefore, drilling waste management is of particular importance. Electrokinetic (EK) remediation is one of the methods used to remediate all types of soils contaminated with metal and organic pollutants, but the special conditions and properties of drilling wastes make the use of this method more complex for the treatment of this type of waste. In this study, by enhancing the EK method with Fenton technique, which is an advanced oxidation technique, and using copper and iron electrodes as anode, total petroleum hydrocarbons (TPH) were removed from the oil-based drilling waste. The best result in this study was obtained by reducing the initial concentration of TPH from 316,000 to 72,680 mg⁄kg in drilling waste. This 77 % reduction in TPH concentration was achieved using the EK method coupled with Fenton technique along with the use of copper electrode. The use of iron electrode in the EK-Fenton (EK-F) method improved the parameters affecting the removal efficiency and pollutants decomposition and resulted in 69.6 % TPH removal. These results show a 161 % (copper) and 136 % (iron) increase in TPH removal efficiency, respectively, compared to the conventional EK method, in which TPH removal was 29.4 %. These results indicate that the use of EK-Fenton method combined with copper electrode is effective in removing TPH from drilling waste. Overall, the promising results of the present study indicate that the enhanced EK technique could be considered as an effective and environmentally friendly approach for the drilling waste remediation.

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

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

Biodegradation of total petroleum hydrocarbons in contaminated soils using indigenous bacterial consortium

Background: Biodegradation of hydrocarbon compounds is a great environmental concern due to their toxic nature and ubiquitous occurrence. In this study, biodegradation potential of oily soils was investigated in an oil field using indigenous bacterial consortium. Methods: The bacterial strains present in the contaminated and non-contaminated soils were identified via DNA extraction using 16S rDNA gene sequencing during six months. Furthermore, total petroleum hydrocarbons (TPH) were removed from oil-contaminated soils. The TPH values were determined using a gas chromatograph equipped with a flame ionization detector (GC-FID). Results: The bacterial consortium identified in oil-contaminated soils (case) belonged to the families Halomonadaceae (91.5%) and Bacillaceae (8.5%), which was significantly different from those identified in non-contaminated soils (control) belonging to the families Enterobacteriaceae (84.6%), Paenibacillaceae (6%), and Bacillaceae (9.4%). It was revealed that the diversity of bacterial strains was less in oil-contaminated soils and varied significantly between case and control samples. Indigenous bacterial consortium was used in oil-contaminated soils without need for amplification of heterogeneous bacteria and the results showed that the identified bacterial strains could be introduced as a sufficient consortium for biodegradation of oil-contaminated soils with similar texture, which is one of the innovative aspects of this research. Conclusion: An oil-contaminated soil sample with TPH concentration of 1640 mg/kg was subjected to bioremediation during 6 months using indigenous bacterial consortium and a TPH removal efficiency of 28.1% was obtained.

Biodegradation of Total Petroleum Hydrocarbons in Soil: Isolation and Characterization of Bacterial Strains from Oil Contaminated Soil

In this study, we isolated seven strains (termed BY1–7) from polluted soil at an oil station and evaluated their abilities to degrade total petroleum hydrocarbons (TPHs). Following 16 rRNA sequence analysis, the strains were identified as belonging to the genera Bacillus, Acinetobacter, Sphingobium, Rhodococcus, and Pseudomonas, respectively. Growth characterization studies indicated that the optimal growth conditions for the majority of the strains was at 30 °C, with a pH value of approximately 7. Under these conditions, the strains showed a high TPH removal efficiency (50%) after incubation in beef extract peptone medium for seven days. Additionally, we investigated the effect of different growth media on growth impact factors that could potentially affect the strains’ biodegradation rates. Our results suggest a potential application for these strains to facilitate the biodegradation of TPH-contaminated soil.

Effective scale-up of oily sludge bioremediation from a culture-based medium to a two-phase composting system using an isolated hydrocarbon-degrading bacterium: effect of two-step bioaugmentation

The scale-up feasibility of oily sludge (OS) biodegradation from a culture-based medium to a new two-stage composting process bioaugmentated with an indigenous isolated strain was surveyed. First, the bacterial strain (Enterobacter hormaechei strain KA6) was isolated from OS, and then its ability in biomass production and oil degradation in culture-based medium was evaluated. Finally, the strain was used for bioaugmentation in composting reactors which included four in-vessel experiments with the initial total petroleum hydrocarbon (TPHs) concentrations between 10 and 30 g kg-1. The strain was added twice to the composting reactors which lasted 16 weeks including the primary composting stage (PCS) (first inoculation) and the secondary composting stage (SCS) (second inoculation). It was observed that the strain degraded 58.67, 74.79, 45.33, 10.66, and 5.92% of 1, 2, 3, 4, and 5% oil concentrations, respectively, in culture-based medium during 7 days. Regarding OS bioremediation in the composting experiments, a total TPH removal rate of 65.83–81.50% was also reached after the two-stage duration of 16 weeks. Due to the second bioaugmentation stage, the SCS showed higher TPH removal efficiency than the PCS. The study confirmed the effectiveness of the scaling-up of a culture-based medium to a composting process for treating OS.

Combined effects of soil particle size with washing time and soil-to-water ratio on removal of total petroleum hydrocarbon from fuel contaminated soil

In this study, total petroleum hydrocarbon (TPH) removal from fuel-contaminated field soil was investigated. The influence of the washing method (washing before/after sieving), washing time, soil-to-water ratio, and soil particle size on TPH removal efficiency was evaluated under constant stirring speed. Washing the whole contaminated soil is more efficient than separating the soils into particle size fractions and separately washing the fractions. Particles with differing diameters would be more in contact with each other resulting in detachment of contaminants from the soil particle surface. Effects of soil washing time and soil-to-water ratio on TPH removal were not significant in coarse soil particles (greater than 0.15 mm diameter) but significantly affected TPH removal in fine particles (less than 0.15 mm diameter). This study suggests a threshold washing time of 1 h and a threshold soil-to-water ratio of 1:6 for the whole soil in soil washing. However, soil particles less than 0.075 mm (<75 μm) should be separated after washing to meet the Korean soil TPH limit of less than 500 mg/kg. This study demonstrates the importance of finer soils as debrading media and particle size fraction composition of fuel-contaminated soil in soil washing.

Remediation of an oil-contaminated soil by two native plants treated with biochar and mycorrhizae

Soil contamination by petroleum compounds threatens the health of soil and water resources. This research was conducted with the objective of reaching an efficient technique for the removal or reduction of harmful effects caused by total petroleum hydrocarbons (TPH) in soils. In a greenhouse experiment, the effect of biochar (B), mycorrhizae (M) and combination of mycorrhizae and biochar (M + B) on the growth of two native species; clover (Trifolium arvense) and mallow (Malva sylvestris L.), and removal efficiency of TPH (16.79 mg kg-1) from an oil-contaminated soil were studied. The plant analyses after 50 days of growth period showed a significant (p ≤ 0.05) increase in shoot dry weight of mallow in B and M + B treatments but no significant effect was observed for clover compared to the control (C). The initial TPH concentration, determined by gas chromatography technique was reduced from 9.4% in unplanted soil until 56.4% (clover) and 55.9% (mallow) in M + B treatment. The relative concentration of long chain alkanes (LCAs) were also reduced when treatments were applied, in which the highest and lowest reductions was found in C21–C25 and C11–C15, respectively, though octacosane (C28) was increased or unchanged in soil. This result suggests that likely the occurrence of C28 in the mycorrhizal hyphae or the higher removal of the other alkanes increase octacosane relative concentration in soil, which more research is necessary.

The Succession of Dominant Culturable Hydrocarbon-Utilizing Bacteria During Bioremediation of Oil-Based Drilling Waste

Drilling operations of petroleum generate oily wastes. The disposal of a significant amount of oil-based drill muds has caused soil contamination and critical environmental impacts in the last decades.The current study aimed to investigate the potential of microbial remediation for an aged oil-based drilling waste and to monitor the fluctuation in microbial population throughout a 60-day microcosm experiment. A representative aged oil-based drilling waste sample was obtained randomly from a contaminated mud pit in the Khangiran district, Iran. Respiration measurement was performed according to the method described by standard ISO 17155. Total petroleum hydrocarbon (TPH) was measured by the gravimetric method. Microbial counts were measured at 10-day intervals during 60 days of incubation. Total heterotrophic bacteria were enumerated by standard plate count using R2A agar. Dominant heterotrophic and hydrocarbon-utilizing bacteria were selected for phylogenetic analysis. Statistical analyses of the experimental data, using one-way ANOVA were performed using Minitab 16. Following the biostimulation of the contaminated soil, both heterotrophic and hydrocarbon-utilizing bacterial counts increased to above three orders of magnitude in less than 20 days. The highest respiration level and hydrocarbon degradation efficiency were correlated and measured between the 10th and 20th days of the experiment to be 70.7 µg/g.soil.hand 23.13% respectively. Phylogenetic analyses indicated that the members of Actinobacteria (Georgenia, Brevibacterium, Micromonospora, and Streptomyces) were the major hydrocarbon-utilizing bacteria in the microcosm, among which the species of genus Georgenia were dominant throughout the experiments. Furthermore, the population of Alcanivorax species increased promptly and thrived in the microcosm during the active bioremediation phase which indicated their vital role for remediation of diesel range hydrocarbons in saline environments. In an overall view, elegant diversity of hydrocarbon utilizing bacteria along with the accomplished TPH removal efficiency of 45.4% (w/w) in the microcosms, confirmed the potential of indigenous microorganisms for bioremediation of the aged oil-based drilling waste.

Treatment of Diesel Oil Contaminated Soil by Ex-situ Bioremediation

Treatment of oil-polluted soil is a challenging problem faced by all refineries and petrochemical industries. In this research study, bioremediation of diesel oil contaminated soil was conducted for diesel concentration ranging from 5% to 20%. The physicochemical characteristics of diesel oil contaminated soil were studied. The effects of soil amendments, namely coconut ash powder, biofilter activated sludge, and NPK fertilizer, on total petroleum hydrocarbon removal efficiency were studied. The maximum total petroleum hydrocarbon removal efficiency achieved was 94.5% when 4g NPK, 40g of activated sludge and 40g of coconut ash powder per 1000g of contaminated soil were used. The studies on the effect of temperature confirmed the optimal temperature as 35°C. The parametric studies confirmed that the degradation efficiency decreased with increase in diesel oil concentration.

Degradation of petroleum hydrocarbons in unsaturated soil and effects on subsequent biodegradation by potassium permanganate

To date, the oxidation of petroleum hydrocarbons using permanganate has been investigated rarely. Only a few studies on the remediation of unsaturated soil using permanganate can be found in the literature. This is, to the best of our knowledge, the first study conducted using permanganate pretreatment to degrade petroleum hydrocarbons in unsaturated soil in combination with subsequent bioaugmentation. The pretreatment of diesel-contaminated unsaturated soil with 0.5-pore-volume (5%) potassium permanganate (PP) by solution pouring and foam spraying (with a surfactant) achieved the total petroleum hydrocarbon (TPH) removal efficiencies of 37% and 72.1%, respectively. The PP foam, when coupled with bioaugmentation foam, further degraded the TPH to a final concentration of 438mg/kg (92.1% total reduction). The experiment was conducted without soil mixing or disturbance. The relatively high TPH removal efficiency achieved by the PP-bioaugmentation serial foam application may be attributed to an increase in soil pH caused by the PP and effective infiltration of the remediation agent by foaming. The applied PP foam increased the pH of the acidic soil, thus enhancing microbial activity. The first-order biodegradation rate after PP oxidation was calculated to be 0.068d-1. Furthermore, 94% of the group of relatively persistent hydrocarbons (C18-C22) was removed by PP-bioaugmentation, as verified by chromatogram peaks. Some physicochemical parameters related to contaminant removal efficiency were also evaluated. The results reveal that PP can degrade soil TPH and significantly enhance the biodegradation rate in unsaturated diesel-contaminated soil when combined with bioaugmentation foam.

Development of plant-microbe phytoremediation system for petroleum hydrocarbon degradation: An insight from alkb gene expression and phytotoxicity analysis

Aim of present work was to assess in-planta association potential of isolated endophytic bacterial strain Pseudomonas sp. (J10) (KY608252) with two cultivars of Lolium perenne L. (small & jumbo) and Arabidopsis thaliana L. for total petroleum hydrocarbon (TPH) degradation, alkane monooxygenase (alkb) gene expression and phytotoxicity analysis. A plant-microbe phytoremediation system was established to investigate the bacteria's ability to colonize the plant body and quantification of alkb gene to help withstand TPH stress in soil as well as in hydroponics. A real-time PCR method was developed to analyze bacterial colonization and survival within the plant body. Analysis revealed that J10 efficiently colonized all the tested plant species and expressed alkb gene under hydrocarbon stress ranging between 3.7 × 102–3.9 × 106 in A. thaliana and L. perenne (small), respectively. The colonization was more pronounced in soil as compared to hydroponic system. J10 inoculation reduced phytotoxicity and suggested that inoculation had a positive effect on plant growth under stress conditions as compared to control. L. perenne (small) showed significant TPH removal efficiency (45.6%) followed by L. perenne jumbo (24.5%) and A. thaliana (6.2%). In hydroponics, L. perenne (small) degraded about 28.2% TPH followed by L. perenne (jumbo) as 24.4%. Potential of the indigenously isolated plant endophytes may be exploited further for phytoremediation efficiency and industrial applications.

Bioremediation of petroleum-contaminated soil enhanced by aged refuse

In this study, the effect of aged refuse on biodegradation of total petroleum hydrocarbons (TPH), microbial counts, soil ecotoxicity, dehydrogenase activity and microbial community compositions were investigated in solid phase reactors during a 30-week period. The results demonstrate that the removal efficiency of TPH was significantly higher in the soil supplemented with aged refuse than in the soil without aged refuse. After 30 weeks, the removal efficiencies of TPH in soils were 29.3%, 82.1%, 63.7% and 90.2% in the cases of natural attenuation, nutrient addition (with NH4NO3 and K2HPO4), supplement with 20% (w/w, dry weight basis) of aged refuse and the combination of nutrient and aged refuse. Nutrient plus aged refuse made the TPH concentration decrease to below the threshold level of commercial use required for Chinese soil quality for TPH (<3000 mg/kg) in 30 weeks. It was also found that dehydrogenase activity, bacterial counts and degrader abundance in the soil were remarkably enhanced by the addition of aged refuse (20%,w/w). Total organic carbon analysis demonstrates that large amounts of hydrocarbon intermediates occurred in the soil after bioremediation.

Microwave (MW) remediation of hydrocarbon contaminated soil using spent graphite – An approach for waste as a resource

In this study, we have explored the possibility of using an industrial waste for remediation of heavy fuel oil contaminated soil. Microwave (MW) heating in the presence of spent graphite (SG) from an auto forging industry has been used for the remediation. The physico-chemical characterization of SG and contaminated soil were done. Microwave remediation experiments were conducted in a lab scale unit and the effect of different parameters like microwave power, susceptor loading and treatment time were studied and optimized. The contaminated and decontaminated soils were analysed using GC-MS for total petroleum hydrocarbons (TPH), Total Organic Carbon and CHNS analyzers. Batch experiments of soil remediation showed that the TPH removal efficiencies (%) of 41.25, 87.77 and 91.18 at 300, 450 and 600 W respectively at SG concentration of 2.5 (wt. %) for a reaction time of 60 min. The addition of SG as susceptor enhanced the desorption of long chain hydrocarbons (C12–C29) present in the soil. Desorption of hydrocarbons from the soil fits well with first order kinetic model. This study successfully demonstrated the reuse of spent graphite (a lubricant waste) recovered from metal forging operations for remediating the fuel oil contaminated soil.