Optimisation research of petroleum hydrocarbon biodegradation in weathered drilling wastes from waste pits

Evaluation of the Effectiveness of the Biopreparation in Combination with the Polymer γ-PGA for the Biodegradation of Petroleum Contaminants in Soil

Biodegradation is a method of effectively removing petroleum hydrocarbons from the natural environment. This research focuses on the biodegradation of aliphatic hydrocarbons, monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and all three xylene isomers (BTEX) and polycyclic aromatic hydrocarbons (PAHs) as a result of soil inoculation with a biopreparation A1 based on autochthonous microorganisms and a biopreparation A1 with the addition of γ-PGA. The research used biopreparation A1 made of the following strains: Dietzia sp. IN133, Gordonia sp. IN138 Mycolicibacterium frederiksbergense IN53, Rhodococcus erythropolis IN119, Rhodococcus sp. IN136 and Pseudomonas sp. IN132. The experiments were carried out in laboratory conditions (microbiological tests, respirometric tests, and in semi-technical conditions (ex-situ prism method). The biodegradation efficiency was assessed on the basis of respirometric tests, chromatographic analyses and toxicological tests. As a result of inoculation of AB soil with the biopreparation A1 within 6 months, a reduction of total petroleum hydrocarbons (TPH) (66.03%), BTEX (80.08%) and PAHs (38.86%) was achieved and its toxicity was reduced. Inoculation of AB soil with the biopreparation A1 with the addition of γ-PGA reduced the concentration of TPH, BTEX and PAHs by 79.21%, 90.19%, and 51.18%, respectively, and reduced its toxicity. The conducted research has shown that the addition of γ-PGA affects the efficiency of the biodegradation process of petroleum pollutants, increasing the degree of TPH biodegradation by 13.18%, BTEX by 10.11% and PAHs by 12.32% compared to pure biopreparation A1.

Assessment of the Suitability of Melilotus officinalis for Phytoremediation of Soil Contaminated with Petroleum Hydrocarbons (TPH and PAH), Zn, Pb and Cd Based on Toxicological Tests

The article presents issues related to the possibility of using toxicological tests as a tool to monitor the progress of soil treatment contaminated with petroleum substances (TPH, PAH), Zn, Pb and Cd in bio-phytoremediation processes. In order to reduce the high content of petroleum pollutants (TPH = 56,371 mg kg⁻¹ dry mass, PAH = 139.3 mg kg⁻¹ dry mass), the technology of stepwise soil treatment was applied, including basic bioremediation and inoculation with biopreparations based of indigenous non-pathogenic species of bacteria, fungi and yeasts. As a result of basic bioremediation in laboratory conditions (ex-situ method), the reduction of petroleum pollutants TPH by 33.9% and PAH by 9.5% was achieved. The introduction of inoculation with biopraparation-1 prepared on the basis of non-pathogenic species of indigenous bacteria made it possible to reduce the TPH content by 86.3%, PAH by 40.3%. The use of a biopreparation-1 enriched with indigenous non-pathogenic species of fungi and yeasts in the third series of inoculation increased to an increase in the degree of biodegradation of aliphatic hydrocarbons with long carbon chains and PAH by a further 28.9%. In the next stage of soil treatment after biodegradation processes, which was characterized by an increased content of heavy metals (Zn, Pb, Cd) and naphthalene, chrysene, benzo(a)anthracene and benzo(ghi)perylene belonging to polycyclic aromatic hydrocarbons, phytoremediation with the use of Melilotus officinalis was applied. After the six-month phytoremediation process, the following was achieved: Zn content by 25.1%, Pb by 27.9%, Cd by 23.2% and TPH by 42.2% and PAH by 49.9%. The rate of removal of individual groups of hydrocarbons was in the decreasing order: C₁₂–C₁₈ > C₆–C₁₂ > C₁₈–C₂₅ > C₂₅–C₃₆. PAHs tended to be removed in the following order: chrysene > naphthalene > benzo(a)anthracene > benzo(ghi)perylene. The TF and BCF coefficients were calculated to assess the capacity of M. officinalis to accumulate metal in tissues, uptake from soil and transfer from roots to shoots. The values of TF translocation coefficients were, respectively, for Zn (0.44), Pb (0.12), Cd (0.40). The calculated BCF concentration factors (BCF_roots > BCF_shoots) show that heavy metals taken up by M. officinalis are mainly accumulated in the root tissues in the following order Zn > Pb > Cd, revealing a poor metal translocation from the root to the shoots. This process was carried out in laboratory conditions for a period of 6 months. The process of phytoremediation of contaminated soil using M. officinalis assisted with fertilization was monitored by means of toxicological tests: Microtox, Ostracodtoxkit F^TM, MARA and Phytotoxkit^TM. The performed phytotoxicity tests have indicated variable sensitivity of the tested plants on contaminants occurring in the studied soils, following the sequence: Lepidium sativum < Sorghum saccharatum < Sinapis alba. The sensitivity of toxicological tests was comparable and increased in the order: MARA < Ostracodtoxkit F^TM < Microtox. The results of the toxicological monitoring as a function of the time of soil treatment, together with chemical analyses determining the content of toxicants in soil and biomass M. officinalis, clearly confirmed the effectiveness of the applied concept of bioremediation of soils contaminated with zinc, lead and cadmium in the presence of petroleum hydrocarbons.

Changes in toxicity during in situ bioremediation of weathered drill wastes contaminated with petroleum hydrocarbons

Bioremediation of weathered drill wastes severely contaminated with total petroleum hydrocarbons (TPH) (90,000-170,000 mg kg(-1)) and BTEX (51.2-95.5 mg kg(-1)) to soil standards was achieved over a 3-year period in three phases: initial remediation, basic bioremediation and inoculation with a biopreparation. Fourteen non-pathogenic indigenous bacteria species belonging mainly to the Actinomycetales were identified and shown to be able to degrade 63-75% of nC(9)-nC(20), 36-51% of nC(21)-nC(36), 36% of BTEX and 20% of PAHs (polycyclic aromatic hydrocarbons). Addition of five non-pathogenic fungi species to the bacterial consortium allowed degradation of 69-89% of nC(9)-nC(20), 47-80% of nC(21)-nC(36), 76% of BTEX, and 68% of PAHs. Microtox, Ostacodtoxkit, Phytotoxkit and Ames tests indicated that changes in toxicity were not connected with the decrease in TPH contents, possibly due to the formation of toxic indirect metabolites during bioremediation. No toxicity was found in the soil after bioremediation.

Kinetic modeling and half life study on bioremediation of crude oil dispersed by Corexit 9500

Hydrocarbon pollution in marine ecosystems occurs mainly by accidental oil spills, deliberate discharge of ballast waters from oil tankers and bilge waste discharges; causing site pollution and serious adverse effects on aquatic environments as well as human health. A large number of petroleum hydrocarbons are biodegradable, thus bioremediation has become an important method for the restoration of oil polluted areas. In this research, a series of natural attenuation, crude oil (CO) and dispersed crude oil (DCO) bioremediation experiments of artificially crude oil contaminated seawater was carried out. Bacterial consortiums were identified as Acinetobacter, Alcaligenes, Bacillus, Pseudomonas and Vibrio. First order kinetics described the biodegradation of crude oil. Under abiotic conditions, oil removal was 19.9% while a maximum of 31.8% total petroleum hydrocarbons (TPH) removal was obtained in natural attenuation experiment. All DCO bioreactors demonstrated higher and faster removal than CO bioreactors. Half life times were 28, 32, 38 and 58 days for DCO and 31, 40, 50 and 75 days for CO with oil concentrations of 100, 500, 1000 and 2000 mg/L, respectively. The effectiveness of Corexit 9500 dispersant was monitored in the 45 day study; the results indicated that it improved the crude oil biodegradation rate.