Tank Bottom Sludge Research Articles

Solvent Blend Performance in Hydrocarbon Recovery from Nigerian Tank Bottom Sludge

Oil sludge waste associated with crude oil production generally consists of oil, sands and untreatable emulsions segregated from the production stream, and sediment accumulated on the bottom of crude oil and water storage tanks. The use of single solvent and combination (solvent blend) was evaluated for extraction of hydrocarbon content (oil) of the Tank Bottom Sludge (TBS) associated with the crude oil production with a view to optimizing hydrocarbon recovery from the sludge. TBS samples were contacted with selected solvents blends of varying volumetric ratios, each at a time. The blend generated from xylene, hexane, cyclohexane and petroleum ether representing aliphatic and aromatic interactive combination with varying polarity. Their effects on the oil recovery from tank bottom sludge were determined, with solubility parameter as a factor. The optimum oil recovery by blend A, B and C at room temperature of 29°C, from sample 1 are respectively 54.48% (3:2), 60.33% (2:3) and 61.10% (1:1); from Sample 2, were respectively 66.25% (2:3), 60.80 (3:2) and 63.35 (1:1) at room temperature of 29°C . At room temperature Blend C has the highest performance in extracting oil from sample 1. The highest performance in recovery of oil from sample 2 was observed with blend A (66.25 %.). Solvent extraction process is very effective in recovering hydrocarbons oil from TBS. The use of solvents mixture greatly improved oil recovery from TBS and varies with blend composition and the operating temperature condition.

Solvent Blend Performance in Hydrocarbon Recovery from Nigerian Tank Bottom Sludge

Oil sludge waste associated with crude oil production generally consists of oil, sands and untreatable emulsions segregated from the production stream, and sediment accumulated on the bottom of crude oil and water storage tanks. The use of single solvent and combination (solvent blend) was evaluated for extraction of hydrocarbon content (oil) of the Tank Bottom Sludge (TBS) associated with the crude oil production with a view to optimizing hydrocarbon recovery from the sludge. TBS samples were contacted with selected solvents blends of varying volumetric ratios, each at a time. The blend generated from xylene, hexane, cyclohexane and petroleum ether representing aliphatic and aromatic interactive combination with varying polarity. Their effects on the oil recovery from tank bottom sludge were determined, with solubility parameter as a factor. The optimum oil recovery by blendA,BandCat room temperature of 29°C, from sample 1 are respectively 54.48% (3:2), 60.33% (2:3) and 61.10% (1:1); from Sample 2, were respectively 66.25% (2:3), 60.80 (3:2) and 63.35 (1:1) at room temperature of 29°C . At room temperature BlendChas the highest performance in extracting oil from sample 1. The highest performance in recovery of oil from sample 2 was observed with blendA(66.25 %.). Solvent extraction process is very effective in recovering hydrocarbons oil from TBS. The use of solvents mixture greatly improved oil recovery from TBS and varies with blend composition and the operating temperature condition.

An effective soil slurry bioremediation protocol for the treatment of Libyan soil contaminated with crude oil tank bottom sludge

Petroleum hydrocarbons are the most widespread contaminants in the environment. Soil contamination with crude oil tank bottom sludge (COTBS) represents a significant risk to both human and environmental health. Current traditional approaches only partially resolve the issue as they are inefficient, expensive, not environmentally friendly and leave behind unwanted products; hence, there is an urgent need to develop an environmentally friendly and cost effective solution to address this issue, especially in developing countries. The aim of this study was to develop a slurry phase bioremediation protocol for the treatment of Libyan soil contaminated with crude oil tank bottom sludge (COTBS) at a minimum soil:water ratio using indigenous bacterial isolates. Two hydrocarbonoclastic bacterial isolates, Pseudomonas spp. (4M12) and Pseudomonas xanthomarina (4M14), were used in three different strategies, namely:- bioaugmentation (BA), biostimulation (BS) and biostimulation-bioaugmentation (BS-BA) to assess their ability to reduce the total petroleum hydrocarbon concentration (TPH) in COBTS contaminated Libyan soil. The results indicated that a substantial reduction in TPH was observed in all three treatments, with the BS-BA treatments showing the highest reduction (96–97%, from 30,703 to 860 and 1020 mg kg−1), followed by the BS treatment (92–93% reduction). In contrast, control microcosms showed only a 17.15% reduction (30,667 mg kg−1) in TPH concentration. The results from CO2 respiration, community fingerprinting (DGGE) and metabolic profiling (Biolog assay) confirmed increased activity in the BS/BA treatment. For example, BS-BA treatments produced the highest levels of CO2 after 90 d incubation (0.075 mg day−1 g soil−1 and 0.072 mg day−1 g soil−1) respectively, some 244–258% higher than the control (0.020 mg day−1 g soil−1). This study confirms the potential benefit of the BS-BA approach and the ability of Pseudomonas spp. isolates to significantly reduce the TPH concentration in soil contaminated with COTBS. This approach can be utilized at the commercial scale, as it has lower water requirements than traditional slurry treatments.

Spectroscopic investigations to understand the enhanced dissolution of heavy crude oil in the presence of lactam, alkyl ammonium and hydroxyl ammonium based ionic liquids

The deposition of crude oil in various production and surfaces facilities such as oil storage tanks in the form of tank-bottom sludge, pipeline deposition, skin formation at the near well-bore, deposition in the tubing leads to blockage which invites several operational challenges. These challenges, in turn bring about huge production losses, involvement of scarce human resources, and threatening the environmentally safe operation, thus needing safer solutions. An environmental-friendly method for the dissolution of heavy crude oil (HCO) with the use of ionic liquids (ILs) along with a paraffinic liquid hydrocarbon (organic solvent) is developed which is considered to be very helpful for easy pumping, reducing the risk of manual cleaning and time consumption. In this work, eleven ILs are selected from lactam, alkyl ammonium and hydroxyl ammonium families with various anions, such as, [HCOO]−, [CH3COO]−, [CF3COO]−, [C6H13COO]−. The results on the quantitative and qualitative dissolution of the HCO using organic solvents (with and without ionic liquids) are presented. Studies on the quantitative dissolution of crude oil are performed with the use of UV–vis spectrophotometer, while the qualitative information on the dissolution of HCO are carried out using FT-IR and 13C NMR techniques. In the case of sample system (HCO+solvent+ILs), the increase in solubility observed is up to a maximum of 80%. Time-hold study was conducted for a prolonged period of 30days where the increase in solubility is improved in the range of 80–335% with the addition of ILs along with organic solvents, whereas standard system (without ILs), showed improvement in the range of 11–16% only. This method helps in increasing the efficacy of organic solvents, such as, the liquid hydrocarbons which would be suitable for upstream petroleum engineering application. Moreover, the used ionic liquids were recycled and can also be reused.

Use of Homogeneously-Sized Carbon Steel Ball Bearings to Study Microbially-Influenced Corrosion in Oil Field Samples.

Microbially-influenced corrosion (MIC) contributes to the general corrosion rate (CR), which is typically measured with carbon steel coupons. Here we explore the use of carbon steel ball bearings, referred to as beads (55.0 ± 0.3 mg; Ø = 0.238 cm), for determining CRs. CRs for samples from an oil field in Oceania incubated with beads were determined by the weight loss method, using acid treatment to remove corrosion products. The release of ferrous and ferric iron was also measured and CRs based on weight loss and iron determination were in good agreement. Average CRs were 0.022 mm/yr for eight produced waters with high numbers (105/ml) of acid-producing bacteria (APB), but no sulfate-reducing bacteria (SRB). Average CRs were 0.009 mm/yr for five central processing facility (CPF) waters, which had no APB or SRB due to weekly biocide treatment and 0.036 mm/yr for 2 CPF tank bottom sludges, which had high numbers of APB (106/ml) and SRB (108/ml). Hence, corrosion monitoring with carbon steel beads indicated that biocide treatment of CPF waters decreased the CR, except where biocide did not penetrate. The CR for incubations with 20 ml of a produced water decreased from 0.061 to 0.007 mm/yr when increasing the number of beads from 1 to 40. CRs determined with beads were higher than those with coupons, possibly also due to a higher weight of iron per unit volume used in incubations with coupons. Use of 1 ml syringe columns, containing carbon steel beads, and injected with 10 ml/day of SRB-containing medium for 256 days gave a CR of 0.11 mm/yr under flow conditions. The standard deviation of the distribution of residual bead weights, a measure for the unevenness of the corrosion, increased with increasing CR. The most heavily corroded beads showed significant pitting. Hence the use of uniformly sized carbon steel beads offers new opportunities for screening and monitoring of corrosion including determination of the distribution of corrosion rates, which allows estimation of the probability of high rate events that may lead to failure.

Assessment of the Hydrocarbon Degrading Abilities of Three Bioaugmentation Agents for the Bioremediation of Crude Oil Tank Bottom Sludge Contaminated Libyan Soil

Bioremediation is a widely used environmental friendly treatment method for petrogenic hydrocarbon contaminated soils but its application to the treatment of crude oil tank bottom sludge (COTBS) contaminated soil is limited especially in Mediterranean countries such as Libya. Therefore in this study, the hydrocarbon degrading abilities of three bioaugmentation agents Pseudomonas sp (4M12), Pseudomonas xanthomarina (4M14) and Arthrobacter nitroguajacolicus (1B16A) (isolated from COTBS polluted soils) applied as part of a biostimulation-bioaugmentation (BS/BA) strategy were assessed in COTBS contaminated Libyan soils. Biostimulated (BS) and natural attenuation (NA) microcosms were also set up for comparative purposes. Gas chromatograph mass spectrometer (GC- MS) analysis revealed a total soil petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAHs) content of 30,703 mg kg-1 and 13,816 mg kg-1 respectively. Two carcinogenic fractions (naphthalene and benzenamine, 4, 4`methylenbis [2-methyl-]) and 4 mutagenic fractions (pyrene, phenanthrene, fluorene and anthracene) were detected. Substantial PAH degradation occurred in 4M14 and 4M12 samples within 15 days in contrast to up to 23 days in 1B16A, NA. However, substantial reduction in TPH (> 97%) was only observed in 4M12 and 4M14 inoculated microcosms within 15 days compared to 25-30 days in 1B16A inoculated, BS and NA microcosms. 4M14 inoculated microcosms were most efficient at complete removal (D100) of all carcinogenic and mutagenic fractions; 4M14 (9-10 days), 4M12 (9-15 days), 1B16A (15-23 days), BS (18-21 days) and NA (18-22 days). Pseudomonas xanthomarina was therefore shown as the best candidate for use in a BS/BA approach for treating COTBS contaminated Libyan soils. This study shows the importance of pre-screening bioaugmentation agents for the removal of carcinogenic and mutagenic fractions prior to use; in order to carry out safe, efficient and sustainable COTBS bioremediation in Libya.

Recovery and Characterization of Oil from Waste Crude Oil Tank Bottom Sludge from Azzawiya Oil Refinery in Libya

In this work we present the results of quantitative and qualitative analyses of oil obtained from crude oil tank bottom sludge (COTBS) generated from Azzawiya oil refinery in Libya. The aim of the study was to recover and evaluate oil from waste oily sludge and to compare it with parent oil (Hamada crude oil) in order to assess the commercial potential of recycling the oil. The benefits would be two-fold, firstly to improve oil utilisation efficiency and secondly in reducing the environmental contamination associated with the petrogenic hydrocarbon industry. Oily COTBS and extracted oil were characterised and key properties were measured including water and oil content, light and heavy hydrocarbon content, solid content and organic matter content for COTBS and water content, density, specific gravity, API (American Petroleum Institute) gravity, viscosity, salt and ash content for the extracted oil. Solvent (hexane) extraction confirmed that the oily sludge contained 42.08% (± 1.1%) oil composed of light hydrocarbons (30.7 ± 0.07%) and heavy hydrocarbon (69.3 ± 0.4%) fractions. The water and solid contents were 2.9% (± 0.2%) and 55.02% (± 0.6%) respectively. The properties of the recovered oil were assessed; gas chromatograph spectrophotometer (GC-MS) results indicated that the oil contained 139 different hydrocarbon fractions with a total petroleum hydrocarbon (TPH) concentration of 29,367 mgkg-1 and a polycyclic aromatic hydrocarbons (PAH) concentration of 11,752 mgkg-1. Several parameters of the oil were measured and compared to the parent oil (Hamada crude oil) including density, specific gravity, viscosity, salt and ash content. The API of the extracted oil (33.03) was lower than the parent oil (38.8) due to a reduced light hydrocarbon (LHC) content. TGAFTIR hyphenation shows both mass loss of hydrocarbons— low, medium and high molecular mass over a range of temperatures between 60°C and 450°C. crude oil extract exhibited a non-Newtonian behaviour (shear thinning) for the shear rate sweep between 10 and 500/s. dynamic shear rheology data showed that the extracted oil exhibit more like a solid than liquid. Overall the findings of the study confirmed that COTBD has a significant amount of oil similar in properties to Hamada crude oil. This large amount can be reclaimed and recycles. Depending on this essay, a commercial process could be performed which in parallel will reduce the environmental contamination with hydrocarbons.

Inhibition of Accumulation of Crude Petroleum Storage Tank Bottom Sludge by Using Polymer Dispersants

The study was focused on evaluation of a novel approach for minimizing accumulation of tank bottom sludge during bulk storage of crude oil by using polymer dispersants. Fraction of basic sediments and water remaining in crude oil over a period of 6 months was monitored to assess the effect of additives on extent of settling. At a dose of 100 mg/L, accumulated sludge at the bottom of the container was lower by 20.5 and 22.5 times in the presence carboxymethyl cellulose and polyacrylate, respectively, than in samples without any dispersant. Further, the mechanism behind enhanced stability was investigated through viscosity, particle size, and zeta potential measurements.

Ultrasonic oil recovery and salt removal from refinery tank bottom sludge

The oil recovery and salt removal effects of ultrasonic irradiation on oil refinery tank bottom sludge were investigated, together with those of direct heating. Ultrasonic power, treatment duration, sludge-to-water ratio, and initial sludge-water slurry temperature were examined for their impacts on sludge treatment. It was found that the increased initial slurry temperature could enhance the ultrasonic irradiation performance, especially at lower ultrasonic power level (i.e., 21 W), but the application of higher-power ultrasound could rapidly increase the bulk temperature of slurry. Ultrasonic irradiation had a better oil recovery and salt removal performance than direct heating treatment. More than 60% of PHCs in the sludge was recovered at an ultrasonic power of 75 W, a treatment duration of 6 min, an initial slurry temperature of 25°C, and a sludge-to-water ratio of 1:4, while salt content in the recovered oil was reduced to <5 mg L−1, thereby satisfying the salt requirement in refinery feedstock oil. In general, ultrasonic irradiation could be an effective method in terms of oil recovery and salt removal from refinery oily sludge, but the separated wastewater still contains relatively high concentrations of PHCs and salt which requires proper treatment.

Assessing the hydrocarbon degrading potential of indigenous bacteria isolated from crude oil tank bottom sludge and hydrocarbon-contaminated soil of Azzawiya oil refinery, Libya.

The disposal of hazardous crude oil tank bottom sludge (COTBS) represents a significant waste management burden for South Mediterranean countries. Currently, the application of biological systems (bioremediation) for the treatment of COTBS is not widely practiced in these countries. Therefore, this study aims to develop the potential for bioremediation in this region through assessment of the abilities of indigenous hydrocarbonoclastic microorganisms from Libyan Hamada COTBS for the biotreatment of Libyan COTBS-contaminated environments. Bacteria were isolated from COTBS, COTBS-contaminated soil, treated COTBS-contaminated soil, and uncontaminated soil using Bushnell Hass medium amended with Hamada crude oil (1 %) as the main carbon source. Overall, 49 bacterial phenotypes were detected, and their individual abilities to degrade Hamada crude and selected COBTS fractions (naphthalene, phenanthrene, eicosane, octadecane and hexane) were evaluated using MT2 Biolog plates. Analyses using average well colour development showed that ~90 % of bacterial isolates were capable of utilizing representative aromatic fractions compared to 51 % utilization of representative aliphatics. Interestingly, more hydrocarbonoclastic isolates were obtained from treated contaminated soils (42.9 %) than from COTBS (26.5 %) or COTBS-contaminated (30.6 %) and control (0 %) soils. Hierarchical cluster analysis (HCA) separated the isolates into two clusters with microorganisms in cluster 2 being 1.7- to 5-fold better at hydrocarbon degradation than those in cluster 1. Cluster 2 isolates belonged to the putative hydrocarbon-degrading genera; Pseudomonas, Bacillus, Arthrobacter and Brevundimonas with 57 % of these isolates being obtained from treated COTBS-contaminated soil. Overall, this study demonstrates that the potential for PAH degradation exists for the bioremediation of Hamada COTBS-contaminated environments in Libya. This represents the first report on the isolation of hydrocarbonoclastic bacteria from Libyan COTBS and COTBS-contaminated soil.

Biodegradation of pyrene by a Pseudomonas aeruginosa strain RS1 isolated from refinery sludge.

High molecular weight (HMW) polynuclear aromatic hydrocarbons (PAHs) with more than three rings are inherently difficult to degrade. Degradation of HMW PAHs is primarily reported for actinomycetes, such as, Rhodococcus and Mycobacterium. This study reports pyrene degradation by a Pseudomonas aeruginosa strain isolated from tank bottom sludge in a refinery. High cell surface hydrophobicity induced during growth on pyrene facilitated its utilization as sole carbon source. Specific growth rate (μ) in the range of 0.03-0.085 h(-1) could be achieved over the concentration range 25-500 mg/L. The specific growth rate and specific pyrene utilization rate increased linearly with increase in total pyrene concentration. Although various degradation intermediates were identified in the aqueous phase, accumulation of total organic carbon (TOC) in the aqueous phase was only a small fraction of TOC equivalents of pyrene lost from the cultures. The degradation pathway appears to be similar to that reported for Mycobacterium sp. PYR-I.

Exploiting the intrinsic hydrocarbon-degrading microbial capacities in oil tank bottom sludge and waste soil for sludge bioremediation

In this study, biological methods (biostimulation and bioaugmentation) were used to treat oil tank bottom sludge contaminated soils to total petroleum hydrocarbon (TPH) levels suitable for landfill disposal. The sludge’s hydrocarbon-degrading microbial capacities were initially compared to those from other contaminated environments using culture-based methods. Results indicated that a fungus, Scedosporium dominated the sludge microbial community. Its application in a nutrient formulation resulted in greater reduction in oil tank bottom sludge viscosity (44 %) and residual soil hydrocarbon compared to hydrocarbonoclastic microorganisms from other sources (26.7 % reduction in viscosity). Subsequent field-based experiments showed greater TPH reduction (54 %) in fungal-nutrient-treated sludge–waste soils than in naturally attenuated controls (22 %) over 49 days. 16S ribosomal ribonucleic acid and internal transcribed spacer region-based polymerase chain reactions and denaturing gradient gel electrophoresis analyses showed minimal effects on the microbial communities during this time. TPH reduction to landfill disposal levels occurred at a slower rate after this, falling below the 10,000 mg kg−1 legislated TPH disposal threshold earlier in amended samples (91.2 %; 9,500 mg kg−1) compared to the control (82 %; 17,000 mg kg−1) in 182 days. The results show that the intrinsic hydrocarbon-degrading microbial capacities in sludge are better suited for sludge degradation than those from other sources. The substantial TPH reduction observed in control samples demonstrates the beneficial effects of natural attenuation with waste soils for oil tank sludge treatment. Microbial capacities in sludge and treated waste soils can therefore be successfully employed for treating oil tank bottom sludge.

Ecological risk assessment for small omnivorous mammals exposed to polycyclic aromatic hydrocarbons: A case study in northeastern Mexico

An ecological risk assessment (ERA) was performed using the hazard quotient (HQ) method to evaluate the risks of oral exposure to polycyclic aromatic hydrocarbons (PAHs) for medium sized omnivorous mammals. This is the first in a series of three papers. In Mexico there is little experience in performing this kind of assessment for the terrestrial compartment, in particular for birds and mammals exposed to hydrocarbons. The purpose of this paper is to perform an ERA and to establish if the omnivorous mammalian species living in the area are at risk of adverse effects. The studied site is a land that in past years had been used for the disposition of petroleum tank bottom sludges, and scrap metals. Soil and water samples were collected and analyzed, and we obtained a list of the site's wildlife species as well as samples of the specimens, which were analyzed also. HQs were calculated for the hydrocarbons identified as chemicals of potential ecological concern (COPECs) and the omnivorous mammals of the site were evaluated. Toxicity reference values (TRVs) were taken from the appropriate literature, and the doses of exposure were estimated considering the ingestion of water, soil, and diet. Results indicated that potential risks associated to the oral exposure route were less than benchmarks for effects (in all cases HQ<1). The methodology is adequate in terms of the parameters considered in the calculations, but it was concluded that in order to reduce uncertainty, more research is required in Mexico. This should be primarily aimed at obtaining TRVs for mammals, and consider test species with body weights more similar to those found in the local fauna.

ASIN-Based UWB Radar for Sludge Monitoring

In this paper, we propose an application specific instrument (ASIN)-based ultrawideband (UWB) radar system for sludge monitoring from scattering signatures from the bottom of industrial oil tanks. The method is validated by successful estimation of sludge volume in oil tanks using simulated and real data. First, as a demonstration of the conventional system, image reconstruction algorithms are used for tank-bottom sludge profile imaging for symmetrical and asymmetrical sludge profiles, where the setup is modeled in finite difference time domain method with reduced dimensions of the tank. A 3-D imaging algorithm is used for the 3-D simulation of real life targets. To get the volume of the sludge, ASIN-based UWB radar system is then applied and its effectiveness is demonstrated. In this framework, to get information about the sludge at the bottom of industrial tank, first, a scheme is proposed to differentiate between two sets of data which correspond to two different set of volumes. This method is validated using a commercial UWB kit, in which, practical experiments were performed. The data obtained is visualized using multidimensional scaling procedure and analyzed. Then, regression analysis using radial basis function artificial neuron network is performed, so that given a particular data, it can be predicted that, to which volume it best corresponds.

The Tank Bottom Oily Sludge Characteristics Studying and Treating Processing Researching

The sediments in all kinds of containers in oily field ground processing system were called tank bottom oily sludge. In this paper, the characteristics of sludge were studied. The colloid and asphaltene can increase strength of the oily-water emulsion film which can lead to seriously oily emulsion. In view of this, the process of conditioning-ultrasonic demulsification-centrifugal separation treating tank bottom oily sludge was designed by studying the sludges physical and chemical characteristics. The process parameters were selected. The conditioning were that the dose of detergent was 600 ~ 800 mg/L; The ultrasound processing was that the temperature was 60°C, the ultrasound power was 12Kw and the running time was 25min; The centrifugal separation was that the temperature was 60°C, the dosing flocculant was 600mg/L and centrifuge rotating was 2200r/min. The oily containing in the sludge of centrifugal exports was less than 2% by using this process at the optimal parameters.

Removal of hydrocarbon from refinery tank bottom sludge employing microbial culture

Accumulation of oily sludge is becoming a serious environmental threat, and there has not been much work reported for the removal of hydrocarbon from refinery tank bottom sludge. Effort has been made in this study to investigate the removal of hydrocarbon from refinery sludge by isolated biosurfactant-producing Pseudomonas aeruginosa RS29 strain and explore the biosurfactant for its composition and stability. Laboratory investigation was carried out with this strain to observe its efficacy of removing hydrocarbon from refinery sludge employing whole bacterial culture and culture supernatant to various concentrations of sand-sludge mixture. Removal of hydrocarbon was recorded after 20 days. Analysis of the produced biosurfactant was carried out to get the idea about its stability and composition. The strain could remove up to 85 ± 3 and 55 ± 4.5 % of hydrocarbon from refinery sludge when whole bacterial culture and culture supernatant were used, respectively. Maximum surface tension reduction (26.3 mN m(-1)) was achieved with the strain in just 24 h of time. Emulsification index (E24) was recorded as 100 and 80 % with crude oil and n-hexadecane, respectively. The biosurfactant was confirmed as rhamnolipid containing C8 and C10 fatty acid components and having more mono-rhamnolipid congeners than the di-rhamnolipid ones. The biosurfactant was stable up to 121 °C, pH 2-10, and up to a salinity value of 2-10 % w/v. To our knowledge, this is the first report showing the potentiality of a native strain from the northeast region of India for the efficient removal of hydrocarbon from refinery sludge.

Preparation and characterization of adsorbents for treatment of water associated with oil production

Two sets of adsorbents were prepared from locally available raw materials, characterized and tested. The first set consists of crushed natural attapulgite and crushed attapulgite mixed with petroleum tank-bottom sludge and carbonized at 650°C. Another set was prepared using trunk of date palm tree (Phoenix dactylifera) activated at 700 and 800°C. Both sets were characterized using BET surface area and pore distributions, FTIR, XRD, SEM and TEM. Natural attapulgite and attapulgite/sludge composite exhibited different characteristics and adsorptive capacities for oil removal from oily water. Adsorptive capacities were calculated from the breakthrough curves of a column test. An oily water solution of about 500mg-oil/L was passed through both the attapulgite and attapulgite/sludge columns until the column effluent concentration exceeded a reference limit of 10mg-oil/L. Uptake was calculated at this limit at 155 and 405mg-oil/g-adsorbent, respectively. This was lower than the performance of a commercial activated carbon sample (uptake calculated at 730mg-oil/g-adsorbent). Relatively, the date palm, carbonaceous-based adsorbent samples showed less significant differences in both bulk and surface properties. Uptake significantly improved to 1330–1425mg-oil/g-adsorbent. Attempt was made to associate this performance with the difference in the surface areas between the two sets. However, other factors are found to be important as the second set has a range of surface area less than that of the commercial sample. As evidenced by FTIR, XRD and TEM, the activated carbonaceous materials developed porous structures which form defective graphitic sheet ensembles that serve as additional adsorption sites in the sample.

Removal of Oil Tank Bottom Sludge by Novel Biosurfactant, JE1058BS

Maintenance of crude oil storage tanks requires periodical washing of the tanks before ordinary repairs can be made to these systems. In this study, crude oil derived sludge in the oil storage tank was treated with various surfactants to disperse the sludge into a miscible fraction, including JE1058BS, a new biosurfactant produced by Gordonia sp. strain JE-1058. Phylogenetic analysis of the 16SrRNA sequence of the strain JE-1058 identified Gordonia polyisoprenivorans. The sludge was efficiently removed by dispersion with biosurfactant at concentrations of 1-10 g/L, with stable dispersion at 10 g/L for 3 weeks. Addition of the BS caused no significant changes except for water content in the physicochemical factors such as density, viscosity, and sulfur/nitrogen content, suggesting that the novel biosurfactant JE1058BS is useful for oil tank bottom sludge treatment.

Surfactant Enhanced Biodegradation of Petroleum Hydrocarbons in Oil Refinery Tank Bottom Sludge

Summary Bioremediation has been recognized as an effective method to treat petroleum hydrocarbon pollutants. However, the biodegradation of crude oil-contaminated sludge could be a time-consuming and low-efficiency process. Among the reasons is that some petroleum hydrocarbons in the sludge are unavailable for micro-organisms? utilization. Surfactants have the potential to increase the bioavailability of such pollutants because of their capability to reduce the surface and interfacial tension and increase the solubility of hydrocarbons in water. In this study, the addition of two different chemical surfactants (Igepal CO-630 and Cedephos FA-600) were tested using a laboratory respirometer, and the effects of such surfactants on the biodegradation of total petroleum hydrocarbon (TPH) in the oil refinery sludge were investigated. Both surfactants have been found to be effective on improving microbial growth at low-concentration additions, while the concentration of 400 mg/kg has been found most effective for improving TPH (C10-C50) reduction after 14 days of biodegradation.

Solidification of Tank Bottom Sludge

Tank bottom oily sludge (S) is collected from tank bottoms during cleaning operations and contaminated soil is collected after spills and leakages. Disposal of tank sludge is a significant item of tank maintenance for producers, refiners and transporters of petroleum materials. The objective of this paper is to investigate the use of various additives in the solidification of tank bottom sludge. The sludge was solidified using various combinations of additives including ordinary Portland cement (OPC), cement by-pass dust (CBPD) and quarry fines (QF). Geotechnical and leachability properties of the mixtures were determined. The use of OPC alone as a solidifying agent yielded the best results. This was followed by blends S:OPC:QF of 1:0.5:1.5 and S:CBPD of 1:2. Economically, the latter two mixtures would be considered more cost-effective in solidifying the sludge as the additives are waste by-product materials. The Toxicity Characteristic Leaching Procedure (TCLP) results indicated that no extracts exceeded the threshold TCLP limits established by U.S. Environmental Protection Agency (USEPA). The solidified material can be used in construction of roads, embankments and landfill layers.