Enhanced crude oil biodegradation in soil via biostimulation

Combination of slurry-bioreactors and actinobacteria consortia as strategy to bioremediate chlordane-contaminated soils

Soil contamination caused by pesticides poses a significant environmental challenge, and addressing it requires effective solutions. Bioremediation, combining the utilization of slurry-bioreactors and microbial consortia, emerges as an appropiated strategy to tackle this issue. Therefore, this research evaluated the chlordane (CLD) removal efficiency by a Streptomyces consortium through bioaugmentation of polluted soils, and slurry-bioreactors. For that, a Streptomyces defined consortium with CLD removal abilities was inoculated in soil microcosms and soil-slurry bioreactors (SB), with (SB-TSB) and without stimulation (SB-water). In soil, CLD presence has no negative effect on consortium growth. This was supported by comparing its duplication time (7.48 ± 0.14 h) with the obtained in the biotic control (7.45 ± 0.04 h). Furthermore, 17% of pesticide removal by microbial action was detected in the treated microcosms. In SB, the microbial development was not affected by the pesticide presence. In SB-TSB, the microbial growth was higher than in SB-water. This was supported by its lesser duplication time (7.27 ± 0.17 h) with respect to the non-stimulated systems (10.88 ± 0.29 h). However, SB-water showed the highest CLD removal ability (34.8%), with a concomitant increase in the chloride ion release. In the phytotoxicity test, the vigor index showed that the bioremediation in SB-water did not exert adverse effects greater than those generated by the CLD. Indeed, the root length increased after the treatment. These findings demonstrate the versatility of the Streptomyces consortium to remediate solid and semi-solid matrices impacted with pesticides, and the advantage of using bioaugmented SB to enhance the pollutants removal and accelerating the clean-up time required.

Efficient removal of heavily oil-contaminated soil using a combination of fenton pre-oxidation with biostimulated iron and bioremediation

Crude oil contamination severely deteriorates soils quality. Bioremediation utilizing soil indigenous organisms could be employed to decompose petroleum hydrocarbons thanks to its low cost and minor environmental disturbance. However, slow kinetics limit the successful application of this biotechnique. Pretreating oil-contaminated soils with Fenton pre-oxidation could accelerate the subsequent bioremediation process. This study was to explore the mechanisms behind the rapid propagation of indigenous petroleum-degrading bacteria (IPDB) and the efficient degradation of total petroleum hydrocarbons (TPH) in soil after Fenton pre-oxidation with biostimulated iron. Biostimulated iron and non-biostimulated iron were used in the experiments, where Fenton pre-oxidation was combined with the bioremediation of oil-contaminated soil (TPH = 13221 mg/kg). Although the amount of Fenton pre-oxidized TPH (3331-3775 mg/kg) was similar with biostimulated and non-biostimulated irons, the biodegradation of TPH after Fenton pre-oxidation with biostimulated iron (5840 mg/kg) was much higher than that with non-biostimulated iron (3034-4034 mg/kg). Moreover, abundant nutrients and a high population of residual IPDB were found after Fenton pre-oxidation with biostimulated iron, which benefited stable consumption of NH₃-N and dissolved organic carbon (DOC) by IPDB during the subsequent bioremediation. However, Fenton pre-oxidation with non-biostimulated iron either resulted in greater damage to IPDB or produced fewer nutrients, thereby failing to ensure the continuous propagation of IPDB during the subsequent bioremediation. Therefore, we propose that Fenton pre-oxidation with biostimulated iron should be applied to heavily oil-contaminated soils prior to bioremediation.

Combined biostimulation and bioaugmentation for chlorpyrifos degradation in laboratory microcosms

Chlorpyrifos (CP) is a persistent organophosphorus pesticide (OP) used in soil ecosystem for insect control. Bioremediation process has been proven promising in degrading these toxic molecules and restoring the physio-chemical properties of soil. This work reports a laboratory microcosm study in both non-sterile & sterile conditions, conducted over a period of 56 days to examine the combined effect of additional supplements like biostimulants (BSs) such as N, P, and K in the presence of suitable carrier materials (compost, wheat straw, and corncob) along with bioaugmentation by a Ochrobactrum sp. CPD-03 on CP degradation from the contaminated soil. CP degradation was thoroughly monitored at an interval of 7 days over a period of 56 days. Results showed biostimulation and bioaugmentation along with compost as carrier material had shown higher CP degradation efficiency of 76 ± 2.8 and 74 ± 1.6% in non-sterile and sterile microcosms over a period of 56 days. Moreover, bacterial community profiling (16s rRNA and opd gene) demonstrated increased microbial counts, corroborating the efficiency of the bioremediation process. The survival of CPD-03 at the end of the assay validated its ability of colonizing modified soils. By this integrated method with compost as carrier material, bioremediation process could be enhanced for restoration CP-contaminated soils.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02980-9.

Mitigation of petroleum-hydrocarbon-contaminated hazardous soils using organic amendments: A review

The term "Total petroleum hydrocarbons" (TPH) is used to describe a complex mixture of petroleum-based hydrocarbons primarily derived from crude oil. Those compounds are considered as persistent organic pollutants in the terrestrial environment. A wide array of organic amendments is increasingly used for the remediation of TPH-contaminated soils. Organic amendments not only supply a source of carbon and nutrients but also add exogenous beneficial microorganisms to enhance the TPH degradation rate, thereby improving the soil health. Two fundamental approaches can be contemplated within the context of remediation of TPH-contaminated soils using organic amendments: (i) enhanced TPH sorption to the exogenous organic matter (immobilization) as it reduces the bioavailability of the contaminants, and (ii) increasing the solubility of the contaminants by supplying desorbing agents (mobilization) for enhancing the subsequent biodegradation. Net immobilization and mobilization of TPH have both been observed following the application of organic amendments to contaminated soils. This review examines the mechanisms for the enhanced remediation of TPH-contaminated soils by organic amendments and discusses the influencing factors in relation to sequestration, bioavailability, and subsequent biodegradation of TPH in soils. The uncertainty of mechanisms for various organic amendments in TPH remediation processes remains a critical area of future research.

Mixing of plant litters strengthens their remediation effects on crude oil-contaminated soil

To investigate the effects of the mixing of litters on their remediation efficiency in petroleum-contaminated soil, litters from two common plants in the petroleum-contaminated region of Northern Shaanxi, China, Bothriochloa ischaemum (L.) Keng and Sophora davidii Kom. ex Pavol., and their mixture were mixed with 45 g/kg petroleum-contaminated soil. Based on these, a 150-day simulated remediation experiment was conducted at 25 °C and consistent moisture conditions. The effects on the degradation of petroleum components and the restoration of nutrient contents, pH, and enzymatic activity in the disturbed soil were detected. The effects of the litter treatments on the community structure and carbon source utilization characteristics of soil microorganisms were also studied. The results indicated that all litter treatments significantly accelerated the degradation of petroleum components, while the mixing of litter exhibited significant synergistic effects, leading to significantly higher degradation rates of saturated hydrocarbons, aromatic hydrocarbons, and nonhydrocarbon substances than the observed rates in the single-litter treatments and the predicted rates based on the single-litter treatments. Litter treatment significantly increased the N and P contents and enzymatic activity of contaminated soil. The effects of mixed litter on soil chemical and biological properties fell between the effects of the 2 types of single-litter treatments. However, the mixing of litters exhibited significant synergistic effects in supplementing available P and increasing sucrase, dehydrogenase, lignin peroxidase, and laccase activity, while it exhibited significant antagonistic effects in supplementing nitrate nitrogen and increasing urease, phosphatase, polyphenol oxidase, and manganese peroxidase activity. Litter treatment significantly altered the community structure of soil microorganisms. The relative abundances of some petroleum-degrading microbial phyla or genera in mixed litter-treated soil were significantly different from those in single litter-treated soils, which might contribute to the strengthened remediation effects of mixed litter treatment. The results might provide a theoretical basis for the more effect utilization of biomass resources in the remediation of petroleum-contaminated soil.

Strategy to improve crude oil biodegradation in oligotrophic aquatic environments: W/O/W fertilized emulsions and hydrocarbonoclastic bacteria

We studied petroleum biodegradation by biostimulation by using water in oil in water (W/O/W) double emulsions. These emulsions were developed using seawater, canola oil, surfactants, and mineral salts as sources of NPK. The emulsions were used in the simulation of hydrocarbon bioremediation in oligotrophic sea water. Hydrocarbon biodegradation was evaluated by CO2 emissions from microcosms. We also evaluated the release of inorganic nutrients and the stability of the emulsion's droplets. The double emulsions improved CO2 emission from the microcosms, suggesting the increase in the hydrocarbon biodegradation. Mineral nutrients were gradually released from the emulsions supporting the hydrocarbon biodegradation. This was attributed to the formation of different diameters of droplets and therefore, varying stabilities of the droplets. Addition of the selected hydrocarbonoclastic isolates simulating bioaugmentation improved the hydrocarbon biodegradation. We conclude that the nutrient-rich W/O/W emulsion developed in this study is an effective biostimulation agent for bioremediation in oligotrophic aquatic environments.

Coupling of bioaugmentation and biostimulation to improve lindane removal from different soil types

Lindane is an organochlorine pesticide that, due to its persistence in the environment, is still detected in different matrices. Bioremediation using actinobacteria consortia proved to be promising for the restoration of contaminated soils. Another alternative to remove xenobiotics is to use agricultural residues, which stimulates microbial activity, increasing its capacity to degrade organic pollutants. The present work studies the coupling of sugarcane bagasse biostimulation and bioaugmentation with the actinobacteria consortium composed of Streptomyces sp. A2, A5, A11 and M7 on lindane removal in different soil types. In this sense, factorial designs with three factors (proportion and size of sugarcane bagasse particles, and moisture content) were employed. A response optimizer identified the combination of factors levels that jointly allowed obtaining the maximum lindane removal in the evaluated conditions. In the optimal conditions, the effect of the bioremediation process on soil microbiota was studied by evaluating different parameters. The highest lindane removal percentages were detected in biostimulated microcosms bioaugmented with the microbial consortium, which were accompanied by a decrease in lindane half-life respect to the controls. Also, the bioaugmentation of biostimulated microcosms increased the microbial counts and enhanced soil enzymatic activities, corroborating the bioremediation process efficiency. The survival of the four actinobacteria at the end of the assay confirmed the ability of all Streptomyces strains to colonize amended soils. Bioremediation by simultaneous application of biostimulation with sugarcane bagasse and bioaugmentation with the actinobacteria consortium, in the optimized conditions, represents an efficient strategy to restore lindane contaminated soils.

Fungal proliferation and hydrocarbon removal during biostimulation of oily sludge with high total petroleum hydrocarbon

A laboratory-scale study was conducted to investigate the effect of bioaugmentation (BA) and biostimulation (BS) on the remediation of oily sludge with high total petroleum hydrocarbon (TPH) content (269,000 mg/kg d.w. sludge). TPH concentration significantly decreased by 30.4% (P < 0.05) in the BS treatment after 13-week incubation, and 17.0 and 9.1% of TPH was removed in the BA and control treatments (amended with sterile water only), respectively. Aliphatic and other fractions (i.e., saturated n-alkanes and cyclic saturated alkanes) were reduced in the BS treatment, whereas no decrease in aromatic hydrocarbons occurred in any treatment. Gas chromatography-mass spectrometry analysis of aliphatic fractions showed that low-chain-length alkanes (C8-C20) were the most biodegradable fractions. The BS treatment supported fungal proliferation, with Sordariomycetes and Eurotiomycetes as the dominant classes. BS increased fungal diversity and decreased fungal abundance, and changed bacterial community structure. The findings show the potential of using BS to treat oily sludge with high TPH content. Graphical abstract.

Bioremediation of Polluted Soil Sites with Crude Oil Hydrocarbons Using Carrot Peel Waste

The biostimulation potentials of carrot peel waste and carob kibbles for bioremediation of crude petroleum-oil polluted soil were investigated. Temperature, pH, moisture, total petroleum hydrocarbon (TPH), and changes in microbial counts during 45 days were monitored when 4 mL of carrot peel waste or carob kibbles media were added to 200 g of crude oil polluted soil samples. Gas chromatography-flame ionization detection (GC-FID) was used to compare hydrocarbon present in the crude oil polluted soil and in pure fuel, composition of crude oil polluted soil was analyzed by X-ray diffraction (XRD), and the TPH was measured by distillation using distiller mud. The results showed that, at the end of experiments, the concentration of TPH decreased in crude oil polluted soil containing carrot peel waste with a percentage of 27 ± 1.90% followed by crude oil polluted soil containing carob kibbles (34 ± 1.80%) and in the unamended control soil (36 ± 1.27%), respectively. The log [Colony Forming Unit (CFU)/g] of total heterotrophic bacteria in the crude oil polluted soil increased from 10.46 ± 0.91 to 13.26 ± 0.84 for carrot peel waste, from 11.01 ± 0.56 to 11.99 ± 0.77 for carob kibbles and from 8.18 ± 0.39 to 8.84 ± 0.84 for control, respectively. Such results demonstrated that carrot peel could be used to enhance activities of the microbial hydrocarbon-degrading bacteria during bioremediation of crude petroleum-oil polluted soil.