Treatment of petroleum drill cuttings using bioaugmentation and biostimulation supplemented with phytoremediation

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.

Petroleum hydrocarbons reduction by selected tropical grass species in oil-based drill cuttings contaminated soil

The potential of phytoremediation of oil-based drill cuttings (OBDCs) contaminated soil was assessed by measuring the level of petroleum hydrocarbons reduction. The contamination experiment was simulated in a randomized complete block design by factorial of 6 × 3 × 2 × 2 for grass species (Pennisitum purpureum, Panicum maximum, Andropogon gayanus, Heteropogon contortus, Axonopus compressus, and Chloris virgata), drill cuttings treatments (0%, 25%, and 50% OBDCs contamination), time (0 day of planting and 105 days of harvesting), and growth stage (young and mature). The parameters assessed were total petroleum hydrocarbons (TPHs) in soils, roots, and shoots; bioconcentration factor in roots and shoots; and translocation factor. The TPH reductions achieved in 25% treatment level were young A. compressus (58.01%), mature P. purpureum, young A. gayanus and C. virgata (44.24%), young P. purpureum (27.67%), mature A. compressus (25.29%), mature H. contortus (2.56%), mature P. maximum (4.01%), and unplanted soils (2.10%). Thus young A. compressus, A. gayanus, C. virgata, and mature P. purpureum are recommended for TPH reduction in 25% OBDCs contaminated soils. Young P. purpureum and mature A. compressus can be used to achieve 25% - 27% TPH reduction.

Phytoremediation of soil contaminated with weathered petroleum hydrocarbons by applying mineral fertilization, an anionic surfactant, or hydrocarbonoclastic bacteria

This study evaluated the effect of the application of mineral fertilization (F), the anionic surfactant Triton X-100 (TX100), or the inoculation with a hydrocarbooclastic bacterial consortium (BCons) on the growth of Clitoria ternatea during the phytoremediation of a Gleysol contaminated with weathered petroleum hydrocarbons (39,000 mg kg^-1 WPH) collected from La Venta, Tabasco (Mexico). The experiment consisted of a completely randomized design with seven treatments and four replications each under greenhouse conditions. The application of F (biostimulation) increased plant growth and biomass production; in contrast, TX100 only favored root biomass (11%) but significantly favored WPH degradation. Bioaugmentation with BCons did not show significant effects on plant growth. Nevertheless, the combination of biostimulation with bioaugmentation (BCons + F, BCons + TX100, and BCons + F+TX100) enhanced plant growth, hydrocarbonoclastic bacteria population, and WPH degradation when compared to treatments with the single application of bioaugmentation (BCons) or biostimulation (F).

Oil bioremediation in soils contaminated with oil spills in tropical environments

Bioremediation techniques like bioaugmentation and/or biostimulation are an economical and environmentally friendly procedure which emerged as the most advantageous methodology for treatment of contaminated sites by oil spills pollutants. This research uses a tropical soil contaminated with oil based drilling fluids (OBMs) and drill cuttings were evaluating at laboratory scale. Seven treatments were implemented separately: (C) control; (A) natural attenuation; (B) compost (Bs) nutrients; (BsT) nutrients and tween 80; (BsTL) nutrients, tween 80, leonardite, and (BL) nutrients, tween 80, leonardite and d-limonene. For three months, changes in Total Petroleum Hydrocarbons (TPH) soil microbial counts and activity were monitored as indicators of biodegradation. In order to evaluate the efficiency of treatments in the microcosm experiments. After 90 days of incubation hydrocarbon biodegradation is 76.2% (C), 28.6% (A), 76.2% (B), 66.7% (Bs), 83.3% (BsT), 69% (BsTL) and 88.1% (BL), respectively. Scanning electron microscopy (SEM) of OBMs evidenced absence of heavy metals. Biodiversity analysis showed a decrease in bacterial diversity and a rise in tolerant genus of hydrocarbons such as Nocardiodes, Streptomyces, Dietzia and Advenella. The co-substrate and stimulants had synergistic effect on the biological degradation of hydrocarbons. This research suggests that the implementation of bioaugmentation and biostimulation methods will be used a larger scale in contaminated sites.

Rhizoremediation as a green technology for the remediation of petroleum hydrocarbon-contaminated soils

Rhizoremediation is increasingly becoming a green and sustainable alternative to physico-chemical methods for remediation of contaminated environments through the utilization of symbiotic relationship between plants and their associated soil microorganisms in the root zone. The overall efficiency can be enhanced by identifying suitable plant-microbe combinations for specific contaminants and supporting the process with the application of appropriate soil amendments. This approach not only involves promoting the existing activity of plants and soil microbes, but also introduces an adequate number of microorganisms with specific catabolic activity. Here, we reviewed recent literature on the main mechanisms and key factors in the rhizoremediation process with a particular focus on soils contaminated with total petroleum hydrocarbon (TPH). We then discuss the potential of different soil amendments to accelerate the remediation efficiency based on biostimulation and bioaugmentation processes. Notwithstanding some successes in well-controlled environments, rhizoremediation of TPH under field conditions is still not widespread and considered less attractive than physico-chemical methods. We catalogued the major pitfalls of this remediation approach at the field scale in TPH-contaminated sites and, provide some applicable situations for the future successful use of in situ rhizoremediation of TPH-contaminated soils.

Investigating the potential of sunflower species, fermented palm wine and Pleurotus ostreatus for treatment of petroleum-contaminated soil

Phyto- and myco-remediation have been identified as sustainable options for treatment of petroleum-contaminated soils. To appraise the benefits thereof, the potentials of 3 sunflower species, 2 palm wine types and P. ostreatus to treat petroleum-contaminated soils was investigated. The study involved sampling of petroleum-contaminated soils and treatment with the phyto- and myco-remediation agents for a period of 90-days. Agents used for the remediation were 3 species of sunflowers (Helianthus annus-pacino gold, Helianthus sunsation &Helianthus annus-sunny dwarf), fermented palm wine (from 2 species of palm trees -Elaeis guineensis &Raffia africana), and oyster mushroom (Pleurotus ostreatus). The study further investigated variation in remediation efficiency among the sunflower and palm wine species, as well as different substrates and conditions for optimal application of P. ostreatus. The results obtained revealed up to 340 g/kg dry weight of Total petroleum hydrocarbons (TPHs) in the soils, with remediation outcomes of up to 69% by the sunflower- Helianthus annus (Pacino gold), 70% by fermented palm wine, and 85% by P. ostreatus. While the remediation efficiency of sunflower species was proportional to biomass, there was no significant difference in remediation efficiency of the palm wines. It was also found that substrates type and method of application has a significant impact on the remediation efficiency of P. ostreatus. The study further revealed available nitrate and electrical conductivity as possible useful indicators of TPHs concentration and remediation progress in soils.

Tolerance and phytoremediation potential of four tropical grass species to land-applied drill cuttings

This work evaluated the tolerance and phytoremediation potential of four tropical grasses over a 12-week period, with a view to assessing their suitability for land farming of oil-based drill cuttings. It considered four grass species, namely, guinea grass (Megathyrsus maximus), spear grass (Imperata cylindrica), gamba grass (Andropogon gayanus), and elephant grass (Pennisetum purpureum). The treatments involved growing each of the four grasses on a mixture of 3:1 soil/drill-cuttings ratio, after failed trials with mix ratios ranging from 1:3 to 2:1 soil/drill-cuttings ratio, and on uncontaminated soil. The TPH concentration dropped by 27-81% from 4805 mg kg^-1 in the 3:1 soil/drill-cuttings mixtures in the different treatments after 12 weeks. Better growth performance in the contaminated treatments, compared to uncontaminated controls, correlated with higher reduction in TPH and metals concentrations. The contaminated elephant grass treatment showed better plant height and leaf sizes than the uncontaminated control. The growth parameters of contaminated treatments with the other three grasses ranged from 29 to 75% of the corresponding uncontaminated controls. The results demonstrate that the relative suitability of the grasses for land farming of oil-based drill cuttings is in the order, elephant grass > guinea grass > gamba grass > spear grass.

Biosurfactant-assisted phytoremediation of multi-contaminated industrial soil using sunflower (Helianthus annuus L.)

This study evaluated the use of commercial rhamnolipid biosurfactant supplementation in the phytoremediation of a soil via sunflower (Helianthus annuus L.) cultivation. The soil, obtained from an industrial area, was co-contaminated with heavy metals and petroleum hydrocarbons. The remediation tests were monitored for 90 days. The best results for removal of contaminants were obtained from the tests in which the sunflower plants were cultivated in soil with 4 mg kg^-1 of the rhamnolipid. Under these conditions, reductions of 58% and 48% were obtained in the total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations, respectively; reductions in the concentrations of the following metals were also achieved: Ni (41%), Cr (30%), Pb (29%), and Zn (20%). The PCR-DGGE analysis of soil samples collected before and after the treatments verified that the plant cultivation and biosurfactants supplementation had little effect on the structure of the dominant bacterial community in the soil. The results indicated that sunflower cultivation with the addition of a biosurfactant is a viable and efficient technology to treat soils co-contaminated with heavy metals and petroleum hydrocarbons.

Agronomic and economic evaluation of Vetiver grass (Vetiveria zizanioides L.) as means for phytoremediation of diesel polluted soils in Israel

Soil pollution in Israel, due to diesel contamination, is a major concern, with gas stations, factories and refineries being the main polluters (>60%). Vetiver grass (Vetiveria zizanioides L.) is a perennial grass belonging to the Poaceae family, and is recognized world-wide for its potential as a plant with phytoremediation traits to contaminated soils. It is demonstrated here to decrease diesel contamination in field and court-yard trials. Chemical soil analysis indicated up to a 79% decrease (P < .05) in diesel pollution of contaminated soil planted with Vetiver; and at high soil contamination levels of 10 L/m², a significant (P < .05) reduction of 96, 96 and 87% was recorded at soil depths of 0-20, 20-40 and 40-60 cm, respectively. Furthermore, in field plots contaminated with diesel and planted with Vetiver, weeds' biomass recovered to non-polluted levels following 8 to 9 months of Vetiver treatment. An economic evaluation conducted based on the cost-benefit analysis (CBA) principles, utilizing the Net Present Value (NPV) compared phytoremediation to other currently used decontamination procedures. The economic comparison showed that phytoremediation cleanup costs are lower and more beneficial to society at large, primarily from an ecosystem services perspective. Combining the results of the agronomic examination with the economic valuation, this research pointed out that phytoremediation with Vetiver has a non-negligible potential, making it a good solution for cleansing diesel from soils on a state-wide scale in Israel and worthy of further research and development.