Phytodegradation of extra heavy oil-based drill cuttings using mature reed wetland: an in situ pilot study

Physical and chemical characterization of drill cuttings: A review

Drill cuttings comprise a mixture of rocks generated during drilling activities of exploration and production of oil and gas. These residues' properties are variable, depending on several drilling parameters and drilled rock composition. Many scientific studies have been published regarding the characterization of these residues. Articles summarizing these residues' characteristics and toxicity data are poorly explored in the literature. This work reviews the principal methods used to characterize drill cuttings and data about these residues' properties. Some authors have reported the large content of Zn in drill cuttings. These cuttings can be associated with base fluids (as olefins, varying from C11 to C18), and some time crude oil (high range of TPH, unresolved complex mixtures, and PAH compounds). Acute and chronic toxicity tests have shown negative impacts of different types of fluids, the components of these fluids, and cuttings on other marine organisms.

Regional distribution, properties, treatment technologies, and resource utilization of oil-based drilling cuttings: A review

Oil-based drilling cuttings (OBDC) are hazardous wastes produced during the extensive use of oil-based drilling mud in oil and gas exploration and development. They have strong mutagenic, carcinogenic, and teratogenic effects and need to be properly disposed of to avoid damaging the natural environment. This paper reviews the recent research progress on the regional distribution, properties, treatment technologies, and resource utilization of OBDC. The advantages and disadvantages of different technologies for removing petroleum pollutants from OBDC were comprehensively analyzed, and required future developments in treatment technologies were proposed.

Soil microbial ecological effect of shale gas oil-based drilling cuttings pyrolysis residue used as soil covering material

The residue derived from oil-based drilling cutting pyrolysis could be used as paving materials. Some petroleum hydrocarbons remain in the residue after pyrolysis and cause severe environmental pollution. In this study, the soil column leaching experiments were carried out under different leaching amounts, and the vertical migration characteristics of petroleum hydrocarbons in soil and the dynamic response mechanism of microorganisms to petroleum hydrocarbons were analyzed. The result showed that the soil pH value and water content with different leaching amounts did not differ significantly, but the vertical migration ability of each petroleum hydrocarbon component was different. In petroleum hydrocarbon contaminated soil, the relative abundance of Proteobacteria maintained a high level (23.6%-60.7%). At the genus level, the relative abundance of Massilia decreased with the leaching amount increased. According to PICRUSt, Monooxygenase [EC: 1.14.13.-] played a significant role in petroleum hydrocarbon degradation. While Long-chain-fatty-acid-CoA ligase [EC: 6.2.1.3] had the highest relative abundance. By studying the influence of shale gas oil-based drilling cuttings pyrolysis residue on soil physical and chemical properties and soil microorganisms, this work provides scientific ecological assessment for the resource application of pyrolysis residue.

Particular pollutants, physical properties, and environmental performance of porous ceramsite materials containing oil-based drilling cuttings residues

The mineral compositions of oil-based drilling cutting residues (ODCRs) were similar to that of clay, which could be used as raw materials for ceramsite. In this study, the maximum addition of ODCRs and the optimum calcination conditions were studied by single factor experiment. The microstructure, phase composition, and element distribution of ceramsite were studied by means of SEM, XRD and EDS. The ceramsite, with a 40% ODCRs content, was calcined at 1000 °C for 2 h. After cooling down, the ceramsite had good physical properties, including low density, low water absorption, and high compressive strength. The bulk density was 850-970 kg/m³, the water absorption was 2.1-10%, and the cylinder compressive strength was 6-11.8 MPa. And most of the heavy metals in ODCRs were effectively solidified. The organic toxic substances were completely burned. The leaching amount of harmful elements met the requirements of Chinese standards. The ceramsite would avoid secondary pollution to the environment. So the ceramsite made from ODCRs can not only improve the processing speed of ODCRs, but also be used as building materials, greening materials, industrial filter materials, etc., and increase its environmental and social benefits.

Fabrication of Low-Temperature Sintering Building Bricks Using Drilling Cutting and Geopolymeric Technology

This study explores the practicability of using drill cutting (DC) as raw material to fabricate building bricks through the high-temperature sintering method and low-temperature geopolymeric setting (LTGS) process. Drilling mud can be recycled and reutilized after certain treatment procedures and is considered as a non-hazardous waste. However, the treatment process is time-consuming and not cost-effective. For the sintering method, low porosity and high mechanical strength bricks can be sintered at temperatures above 800 °C and meet CNS standards. For the low-temperature geopolymeric setting process, sodium silicate was selected as an activating agent for geopolymerization of drill cutting. Several process parameters, such as Si₂O/Na₂O modulus of alkali solution and low-temperature geopolymeric setting temperature, were investigated. The physical and mechanical properties of the fabricated brick were evaluated. According to the test results, 72.4 MPa compressive strength building bricks with low porosity (13.9%) and water absorption (6.0%) can be fabricated with 2.0 Si₂O/Na₂O alkali solution at 500 °C. The drill cutting brick fabricated not only meets the CNS 382.R2002 common brick standard, but also solve its disposal problem.

Utilization of oil-based mud drilling cuttings wastes from shale gas extraction for cement clinker production

A large amount of oil-based mud drilling cuttings (OBMDC) are generated during shale gas extraction, which adversely affects the environment. In order to realize the resource utilization of waste, the object of this paper is to study the feasibility of OBMDC to produce cement clinker. The results showed that at relatively low calcination temperature, adding a certain amount of OBMDC can produce cement clinker successfully and reduce fuel consumption. The compressive strength, hydration performance, and physical characteristics of clinker with 0, 3, 6, and 9% OBMDC were investigated by chemical analysis methods, X-ray diffraction, isothermal calorimetry, mercury intrusion, and energy dispersive spectroscopy. The results showed that the formulated cement has good hydration performance and the compressive strength also meets relevant standards. The heavy metal ions leaching test showed that the preparation of cement clinker by a low amount of OBMDC could effectively reduce the toxicity of OBMDC. In general, the preparation of cement clinker by OBMDC can realize the resource utilization of waste, effectively reduce its toxicity, and play a positive role in environmental protection.

Continuous supercritical water oxidation treatment of oil-based drill cuttings using municipal sewage sludge as diluent

Oil-based drill cuttings (OBDC) is a characteristic hazardous waste that is generated in oil and gas exploration. In this study, two typical OBDCs from shale gas fields were treated in a continuous supercritical water oxidation (SCWO) for the first time. Because both heat value and ash content (AC) in the OBDCs were well beyond the capacity of continuous operation, municipal sewage sludge (MSS) was innovatively adapted as the diluent. A mixed sludge with OBDC addition levels of 10%, 20%, and 30% was tested using a novel SCWO reactor. Mean residence times of reactants in different reaction zones were specifically calculated. Results indicated the organic carbon removal efficiency could reach up to 98.44%. Eight detected heavy metals were found to be almost completely removed into solid products, and the concentrations in liquid products were all below the discharge limits. It was also found that the SCWO reactor exhibited good anti-plugging and anti-corrosion performance. The AC in the feedstock was up to 28.58%. To the best of our knowledge, this has, hitherto, not been achieved in a continuous SCWO operation. This study provides a new approach for harmlessly and completely degrading OBDC, and is also helpful for the industrialization of SCWO technology.

Heavy metal pollution of oil-based drill cuttings at a shale gas drilling field in Chongqing, China: A human health risk assessment for the workers

With the flourish of shale gas industry in China, the characteristic hazardous waste, oil-based drill cuttings (OBDC), was also produced in large quantities. Unlike traditional petroleum industry, shale gas exploitation covers a wider area and there are more well sites, the adverse effects of OBDC piled up around well sites are even greater. This study investigated the pollution status and leaching toxicity of eight heavy metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn) in OBDC of shale gas exploitation, and evaluated the health risks of the drilling workers. The results showed that heavy metal pollution in OBDC was moderate, and the leaching toxicity was far below the standard value. Non-carcinogenic and carcinogenic risks of drilling workers were within an acceptable range. Meanwhile, in order to reduce the health risks of drilling workers, some suggestions are proposed to reduce the exposure risks of workers and the content of heavy metals in OBDC.

Supercritical water oxidation of oil-based drill cuttings

Oil-based drill cuttings (OBDC) are a typical hazardous solid waste that arises from drilling operations in oil and gas fields. The supercritical water oxidation (SCWO) of OBDC was comprehensively investigated in a batch reactor under the conditions of various oxygen coefficients (OC, 1.5-3.5), temperatures (T, 400-500°C) and reaction times (t, 0.5-10min). Preheating experiments indicated that most of the organic compounds in the initial OBDC sample were distributed within gaseous, oil, aqueous and solid phases, with no more than 9.8% of organic compounds converted into inorganic carbon. All tested variables, i.e., OC, T and t, positively affect the transformation of carbon compounds from the oil and solid phases to the aqueous phase and, ultimately, to CO₂. Carbon monoxide is the primary stable intermediate. The total organic carbon (TOC) removal efficiency can reach up to 89.2% within 10min at 500°C. Analysis of the reaction pathways suggests both homogeneous and heterogeneous reactions exist in the reactor. The homogeneous reaction is a typical SCWO reaction that is governed by a free radical mechanism, and the heterogeneous reaction is dominated by mass transfer. The information obtained in this study is useful for further investigation and development of hydrothermal treatment procedures for OBDC.

Characterization of Dietzia cercidiphylli C-1 isolated from extra-heavy oil contaminated soil

Dietzia cercidiphylliC-1 isolated from extra-heavy oil contaminated soil can efficiently degrade extra-heavy oil.

Development of a low-cost, phyto-tunnel system using Portulaca grandiflora and its application for the treatment of dye-containing wastewaters

A phyto-tunnel was developed using a drilled PVC pipe. It was planted with Portulaca grandiflora and used for the treatment of a textile effluent and a dye mixture. COD, BOD, TOC, conductivity, turbidity, total suspended solids and total dissolved solids of the textile effluent, and dye mixture were decreased by 57, 45, 43, 52, 76, 77 and 24 % within 96 h, and 49, 62, 41, 63, 58, 71 and 33 %, within 60 h, respectively, after treatment. The effluent and dye mixture were decolorized up to 87 and 90 % within 96 and 60 h, respectively. Significant induction in activities of lignin peroxidase, tyrosinase and DCIP reductase was observed in root tissues of the plants. FTIR, HPLC and HPTLC of untreated and treated samples showed the formation of new metabolites and preferential dye removal. Phytotoxicity studies revealed the non-toxic nature of the metabolites.

Combined phytoremediation of metal-working fluids with maize plants inoculated with different microorganisms and toxicity assessment of the phytoremediated waste

The aim of this study was to validate the effectiveness of a phytoremediation procedure for metal-working fluids (MWFs) with maize plants growing in hydroponic culture in which the roots grow on esparto fibre and further improve bioremediation potential of the system with root beneficial bacteria, seeking a synergistic effect of the plant-microorganism combination. Chemical oxygen demand (COD), pH, total and type of hydrocarbons measured after phytoremediation indicated that the process with maize plants was successful, as demonstrated by the significant decrease in the parameters measured. This effect was mainly due to the plant although inoculated microorganisms had a relevant effect on the type of remaining hydrocarbons. The success of the phytoremediation process was further confirmed by two toxicity tests, one of them based on chlorophyll fluorescence measurements on maize plants and another one based on cyanobacteria, using a bioluminescent toxicity bioassay; both tests demonstrated that the phytoremediated waste was significantly less toxic than the initial non-phytoremediated MWFs.

Soil TPH concentration estimation using vegetation indices in an oil polluted area of eastern China

Assessing oil pollution using traditional field-based methods over large areas is difficult and expensive. Remote sensing technologies with good spatial and temporal coverage might provide an alternative for monitoring oil pollution by recording the spectral signals of plants growing in polluted soils. Total petroleum hydrocarbon concentrations of soils and the hyperspectral canopy reflectance were measured in wetlands dominated by reeds (Phragmites australis) around oil wells that have been producing oil for approximately 10 years in the Yellow River Delta, eastern China to evaluate the potential of vegetation indices and red edge parameters to estimate soil oil pollution. The detrimental effect of oil pollution on reed communities was confirmed by the evidence that the aboveground biomass decreased from 1076.5 g m⁻² to 5.3 g m⁻² with increasing total petroleum hydrocarbon concentrations ranging from 9.45 mg kg⁻¹ to 652 mg kg⁻¹. The modified chlorophyll absorption ratio index (MCARI) best estimated soil TPH concentration among 20 vegetation indices. The linear model involving MCARI had the highest coefficient of determination (R² = 0.73) and accuracy of prediction (RMSE = 104.2 mg kg⁻¹). For other vegetation indices and red edge parameters, the R² and RMSE values ranged from 0.64 to 0.71 and from 120.2 mg kg⁻¹ to 106.8 mg kg⁻¹ respectively. The traditional broadband normalized difference vegetation index (NDVI), one of the broadband multispectral vegetation indices (BMVIs), produced a prediction (R² = 0.70 and RMSE = 110.1 mg kg⁻¹) similar to that of MCARI. These results corroborated the potential of remote sensing for assessing soil oil pollution in large areas. Traditional BMVIs are still of great value in monitoring soil oil pollution when hyperspectral data are unavailable.

Enhancing degradation of total petroleum hydrocarbons and uptake of heavy metals in a wetland microcosm planted with Phragmites communis by humic acids addition

The effects of humic acid (HA) on heavy-metal uptake by plants and degradation of total petroleum hydrocarbons (TPHs) in a wetland microcosm planted with Phragmites communis were evaluated by comparing waterlogged soils and water-drained upland soils. Experiments were conducted on soils artificially contaminated with heavy metals (Pb, Cu, Cd, Ni) and diesel fuel. HA showed a positive influence on biomass increase for all conditions, but more for belowground than aboveground biomass, and lower in contaminated than uncontaminated soil. The bioavailability and leachability factor (BLF) for all heavy metals except Ni increased with HA addition in both the control and the P. communis planted microcosms, suggesting that more heavy metals could be potentially phytoavailable for plant uptake. Microbial activities were not affected by both heavy metals and TPH contamination, and HA effects on stimulating microbial activities were much greater in the contaminated soil than under uncontaminated conditions. HA addition enhanced the degradation of TPH and n-alkane in waterlogged conditions. The results show that HA can increase the remedial performance in P. communis dominated wetlands simultaneously contaminated with heavy metals and petroleum hydrocarbons and thus prevent contamination of groundwater or other adjacent ecosystems.

Assessment of a process to degrade metal working fluids using Pseudomonas stutzeri CECT 930 and indigenous microbial consortia

The development of a novel biological process to treat metal working fluids (MWFs)-containing effluents at bioreactor scale was pursued in this work. The bacteria Pseudomonas stutzeri CECT 930 was investigated for the first time as an alternative agent for MWF degradation. An adequate medium design and mixing and aeration system, as well as an appropriate microorganism proved to be crucial for reaching high levels of degradation by P. stutzeri and by an indigenous consortium (about 70% and 50% of reduction in total petroleum hydrocarbon content in less than 2 wk, respectively). Additionally, as there is no information in literature trying to kinetically characterize an MWF-polluted effluent degradation process, all the experimental data were fitted to logistic and Luedeking and Piret models, that allowed to elucidate the growth-associated character of the biodegradation process.

Remediation of oil-based drill cuttings through a biosurfactant-based washing followed by a biodegradation treatment

In this study, oil-based drill cuttings were washed by a rhamnolipid solution and then subjected to bioremediation in stainless steel boxes using sawdust as bulking agent. A mixed bacterial culture, mainly containing Pseudomonas, Acinetobacter, Alcaligenes, Agrobacterium, and Comamonas, was used as inoculums. Approximately 83% of organics were removed after washing under optimal conditions (liquid/solid ratio, 3:1; washing time, 20 min; stirring speed, 200 rpm; rhamnolipid concentration, 360 mg/L; temperature, 60 °C), and the total petroleum hydrocarbon concentration of the cuttings dropped from 85,000 to 12,600 mg/kg. In the bioremediation stage, concentrations of saturated and aromatic hydrocarbons decreased to 2140 and 1290 mg/kg, respectively, after 120 days. Ultrahigh-resolution mass spectrometry demonstrated that oxygen- and nitrogen-containing compounds had undergone biodegradation. The results of this study indicate that this two-stage remedial system can reduce treatment time and increase treatment efficiency as compared with a single bioremediation or washing treatment.

Ultrasound enhanced gradient elution of super heavy oil from weathered soils using TX100/SBDS mixed salt micellar solutions

An ultrasound-enhanced five-stage gradient elution system employing mixed solutions of Triton X-100 (TX100), sodium dodecyl benzenesulfonate (SBDS), and salt (abbr. MSTS) was used to elute super heavy oil from weathered soils. The use of ultrasound increased the elution of super heavy oil by 13-14% and improved first-stage dissolution and dispersion by 62%. However, the amount of super heavy oil dissolved or dispersed in the second through fifth elution stages was unchanged by the application of ultrasound. Saturated hydrocarbons were more quickly eluted in the first two stages. During the final three stages the order of elution for the four identified super heavy oil fractions was: asphaltenes>saturated hydrocarbons>aromatics>resins. A large number of elution stages aided in eluting markers containing a large number of C atoms in the absence of ultrasound. The elution at each stage was higher when ultrasound was employed, and ultrasound-enhanced elution is a potentially useful method for removing super heavy oil from weathered soils.

Impact of ultrasonic time on hot water elution of severely biodegraded heavy oil from weathered soils

An ultrasound-enhanced elution system employing water at a temperature of 70 degrees C was used to remedy weathered soils contaminated with severely biodegraded heavy oil (SBHO). The effect of varying the ultrasonic irradiation time from 0 to 1800 s on the elution of SBHO and three characteristic biomarkers (C(26-34) 17alpha 25-norhopanes, C(26-28) TAS, and C(27-29) MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Elution of the three biomarkers was closely related to the carbon number of the marker. C(26-34) 17alpha 25-norhopanes and C(26-28) TAS species with higher carbon numbers and C(27-29) MTAS species with lower carbon numbers were more readily eluted using sonication times of 1080-1800 s, while smaller TAS homologs were more readily eluted after sonication times of 0-360 s. SEM images of samples treated for longer periods revealed larger "bare patches" on the soil surface. The results of XRD and energy spectroscopy experiments indicated that ultrasound irradiation for 1080 s negatively affected the deposition of CaCO(3), but overall improved the mineral and chemical compositions of treated soils and removal of SBHO.

Impact of ultrasonic power density on hot water elution of severely biodegraded heavy oil from weathered soils

An ultrasound-enhanced elution system using water at a temperature of 70 degrees C was employed to remove severely biodegraded heavy oil (SBHO) from weathered soil. The effect of varying the ultrasonic power density from 0 to 100 W L(-1) on the elution of SBHO and three characteristic biomarkers (C(26-34) 17alpha 25-norhopanes, C(26-28) triaromatic steroids (TAS), and C(27-29) methyl triaromatic steroids (MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The amount of SBHO and biomarkers present in the treated soils and eluent had significant negative correlation with increasing ultrasonic power density. Elution of the three biomarkers was closely related to the number of C atoms in the marker: C(26-34) 17alpha 25-norhopanes with more carbon numbers and MTAS homologs with less carbon numbers were more readily eluted at higher power densities. The smaller TAS species were more readily eluted at a power density of less than 60 W L(-1), while larger TAS species displayed improved elution at power densities greater than 60 W L(-1). SEM images of samples treated at higher power densities revealed a more compact SBHO accumulation layer at the water-soil interface. The results of XRD and energy spectroscopy experiments indicated that ultrasound at a power density of 20 W L(-1) was helpful for the formation and sedimentation of calcite, although this effect disappeared at higher power of greater than 60 W L(-1).

Stabilization/solidification of petroleum drill cuttings

A systematic treatability study was conducted for the treatment of drill cuttings, a waste generated during petroleum exploration and production, by stabilization/solidification with Portland cement (CEM I), with the addition of high carbon power plant fly ash (HCFA), an industrial by-product, as a novel sorbent for organic contaminants. A factorial design experiment was adopted to investigate the effects of waste-to-binder ratio, binder formulation, and curing time on response variables including unconfined compressive strength (UCS), hydraulic conductivity, porosity, leachate pH, and acid neutralization capacity (ANC) of the s/s products. Results show that all factors had significant effects on the properties of the s/s products. Drill cuttings and HCFA addition both reduced UCS, but HCFA improved hydraulic conductivity, relative to CEM I only s/s products. Drill cuttings addition had little effect on the ANC of products prepared with CEM I only, and improved that of products containing HCFA. Management options assessment based on performance criteria adapted from regulatory and other guidance suggests that the s/s products could find application as controlled low-strength materials, landfill liner, and landfill daily cover. This work demonstrates how a systematic treatability study can be used to develop a s/s operating window for the management of a particular waste type.

Simultaneous elimination of dissolved and dispersed pollutants from cutting oil wastes using two aqueous phase extraction methods

Oily wastewater experimental study has been accomplished using two aqueous phases extraction methods on the basis of phase separation properties of non-ionic surfactants above the so-called cloud point curve and the solubilization phenomena of coacervate micelles (surfactant rich phase). Two commercial ethoxylate fatty alcohol surfactants (Oxo-C(10)E(3), Oxo-C(15)E(7)) were employed to treat three kinds of cutting oil wastewater, in order to define the conditions promoting cutting oils emulsions destabilization and cloud point extraction possesses simultaneously. Before extraction test, the phase diagrams of binary water/surfactants systems were drawn and the effect of some cutting oil additives on water-surfactant systems was, therefore studied. The results of oily wastewater extraction with respect to wt.% surfactant and temperature were expressed in terms of chemical oxygen demand (COD) of the dilute phase before and after extraction, residual chemical oxygen demand (COD(R)), residual concentrations of surfactant in the dilute phase (X(t,w)) converted to chemical oxygen demand (COD(T)) and the volume fraction of coacervate (phi(c)) at the equilibrium. The results obtained for each parameter which were also represented on three dimensional diagrams using an empirical smoothing method were in agreement with the experimental ones, where the COD(R) was reduced from 55 to 1.1 g O(2)l(-1).

Surface flow constructed wetland for heavy oil-produced water treatment

Heavy oil-produced water from China' Liaohe Oilfield was purified in a surface flow constructed wetland (SFCW) during a 3-yr field experiment. Treatment showed high mean removal efficiencies of 80%, 93%, 88% and 86% for COD, oil, BOD and TKN, respectively for reed bed #1 and 71%, 92%, 77%, and 81% for COD, oil, BOD and TKN, respectively for reed bed #2. The results also showed that in the third year of the system's operation, the oil-produced water had mainly positive impacts on the reed's health parameters. Thus, reed can be used as a feasible wetland macrophyte for treating such wastewater, and this SFCW system can operate for a long time.

Treatment of spent metalworking fluids

Metalworking fluids (MWFs) are widely used for cooling and lubricating during the machining process. The worldwide annual usage is estimated to exceed 2 x 10(9)l and the waste could be more than ten times the usage, as the MWFs have to be diluted prior to use. For UK industry the disposal cost is estimated to be up to pound16 million per year. Used MWFs cause high levels of contamination and rancid odours due to the presence of complex chemicals, biocides, etc., so that their treatment and final disposal must be handled carefully. Conventionally this has been done by combined physical and chemical methods but, with tightened legislation, these routes are no longer acceptable. Now, biological treatment is being increasingly adopted as it seems to offer an alternative with the potential for significant cost saving. However, there are significant difficulties in operating bioreactors, such as maintenance of the stability of the microbial communities present in activated sludge plants (ASP). In order to resolve these problems, four major areas need to be considered: (1) the composition of the spent MWF and its inherent biodegradability, (2) the recalcitrant compounds existing in waste MWFs and their impact on microbes, (3) the nature of the microbial consortia and means of optimising it, e.g, temperature and the practical design of the bioreactor and (4) the requirements for nutrient supplements and optimal control conditions. The potential importance of understanding the microbial community has been studied by the use of molecular biological techniques such as polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), fatty acid methyl ester (FAME) and fluorescent in situ hybridization (FISH). The application of attached biofilm bioreactors and thermophilic aerobic technology (TAT) has also been studied. This review describes recent advances in each of these areas.