I. Uad

Application of bioemulsifiers in soil oil bioremediation processes. Future prospects

Biodegradation is one of the primary mechanisms for elimination of petroleum and other hydrocarbon pollutants from the environment. It is considered an environmentally acceptable way of eliminating oils and fuel because the majority of hydrocarbons in crude oils and refined products are biodegradable. Petroleum hydrocarbon compounds bind to soil components and are difficult to remove and degrade. Bioemulsifiers can emulsify hydrocarbons enhancing their water solubility and increasing the displacement of oily substances from soil particles. For these reasons, inclusion of bioemulsifiers in a bioremediation treatment of a hydrocarbon polluted environment could be really advantageous. There is a useful diversity of bioemulsifiers due to the wide variety of producer microorganisms. Also their chemical compositions and functional properties can be strongly influenced by environmental conditions. The effectiveness of the bioemulsifiers as biostimulating agent in oil bioremediation processes has been demonstrated by several authors in different experimental assays. For example, they have shown to be really efficient in combination with other products frequently used in oil bioremediation such as they are inorganic fertilizer (NPK) and oleophilic fertilizer (i.e. S200C). On the other hand, the bioemulsifiers have shown to be more efficient in the treatment of soil with high percentage of clay. Finally, it has been proved their efficacy in other biotechnological processes such as in situ treatment and biopiles. This paper reviews literature concerning the application of bioemulsifiers in the bioremediation of soil polluted with hydrocarbons, and summarizes aspects of the current knowledge about their industrial application in bioremediation processes.

Treatment of diesel-polluted clay soil employing combined biostimulation in microcosms

The efficiency of inorganic fertilizers as stimulating agents for the bioremediation of oil-polluted environments can be increased with the addition of selected biostimulating compounds. In this study, the efficacy of different biostimulation treatments in the remediation of diesel-polluted soil in purpose-built microcosms has been evaluated. The treatments involved combinations of inorganic fertilizer with (a) Ivey surfactant, (b) Biorem organic fertilizer and (c) ethanol. Microbial activity was evaluated by monitoring the growth of heterotrophic and degrading bacteria and their dehydrogenase activity and carbon dioxide production. Hydrocarbon degradation was monitored by gas chromatography/mass spectrometry. The results showed that all treatments enhanced microbial activity in comparison with natural attenuation and also that the combined treatments generally enhanced hydrocarbon biodegradation in comparison to both natural attenuation and the single inorganic fertilizer treatment. The inorganic fertilizer plus Ivey® surfactant was the most efficient treatment in terms of Total Petroleum Hydrocarbon and light and heavy n-alkanes, showing an index of degradation of 1.4 and 1.3, respectively. Furthermore, biodegradation of heavy and branched n-alkanes was higher in microcosms treated with inorganic fertilizer plus ethanol (Index of degradation values of 1.6 and 1.5, respectively) indicating that combined treatments can be very effective in restoration of contaminated soil.

Response of autochthonous microbiota of diesel polluted soils to land-farming treatments.

This study investigated the response of autochthonous microorganisms of diesel polluted soils to land-farming treatments. Inorganic NPK (nitrogen, phosphorous, and potassium) fertilizer and Ivey surfactant were applied alone or in combination as biostimulating agents. The study was carried out in experimental separated land-farming plots performed with two soils: a sandy clay soil with low biological activity and a sandy clay soil with higher biological activity, contaminated with two concentrations of diesel: 10,000 and 20,000mgkg(-1). Bacterial growth, dehydrogenase activity and CO2 production were the biological parameters evaluated. Non-metric multidimensional scaling analysis proved that moisture content showed a tendency related to microbial growth and that heterotrophic and degrading microorganisms had the best relationship. Initial biological activity of soil influenced the response with 11.1% of variability attributed to this parameter. Soils with low activity had higher degree of response to nutrient addition.

Carbonate Precipitation of Bacterial Strains Isolated from Sediments and Seawater: Formation Mechanisms

This article presents a research study on carbonate formation in solid and liquid media by Thalassospira sp., Halomonas sp., Bacillus pumilus, and Pseudomonas grimontii, four bacterial strains isolated from sediments and deep seawater. As part of this study, we analyzed carbonic anhydrase activity, pH, adsorption of calcium and magnesium ions, and total organic and inorganic carbon. The geochemical program PHREEQC was also used to calculate the mineral saturation indexes in all the cultures. The minerals formed were studied with X-ray diffraction, X-ray dispersive energy microanalysis, and scanning electron microscopy. In addition, all four bacterial strains were found to induce carbonate precipitation and to have carbonic anhydrase activity. Sterile control experiments did not precipitate carbonate. In solid M1 and B4 media, all of the strains precipitated magnesium calcite, whereas in the liquid media, they precipitated different percentages of magnesium calcite, aragonite, and monohydrocalcite. In both cases, small amounts of amorphous precipitates were also produced. This article discusses carbonate formation and the possible role played by metabolic activity, bacterial surfaces and carbonic anhydrase in this process. Finally, the results obtained lead to a hypothesis regarding the importance of carbonate precipitation for the survival of bacteria populations in certain habitats.

Bioprecipitation of Calcium Carbonate Crystals by Bacteria Isolated from Saline Environments Grown in Culture Media Amended with Seawater and Real Brine

The precipitation of calcium carbonate and calcium sulphate by isolated bacteria from seawater and real brine obtained in a desalination plant growth in culture media containing seawater and brine as mineral sources has been studied. However, only bioprecipitation was detected when the bacteria were grown in media with added organic matter. Biomineralization process started rapidly, crystal formation taking place in the beginning a few days after inoculation of media; roughly 90% of total cultivated bacteria showed. Six major colonies with carbonate precipitation capacity dominated bacterial community structure cultivated in heterotrophic platable bacteria medium. Taxonomic identification of these six strains through partial 16S rRNA gene sequences showed their affiliation with Gram-positive Bacillus and Virgibacillus genera. These strains were able to form calcium carbonate minerals, which precipitated as calcite and aragonite crystals and showed bacterial fingerprints or bacteria calcification. Also, carbonic anhydrase activity was observed in three of these isolated bacteria. The results of this research suggest that microbiota isolated from sea water and brine is capable of precipitation of carbonate biominerals, which can occur in situ with mediation of organic matter concentrations. Moreover, calcium carbonate precipitation ability of this microbiota could be of importance in bioremediation of CO2 and calcium in certain environments.

Biostimulation combined treatments for remediation of diesel contaminated soil

Bioremediation is an important technology for the restoration of oil polluted environments by indigenous or selected microorganisms. In general, the rate of biodegradation depends on the number and types of microorganisms, the nature and chemical structure of pollutants to be degraded and the environmental conditions. In this study we have evaluated the efficacy of the application of four different biostimulation treatments for the biodegradation of diesel contaminated soils. The treatments applied involved: (a) the addition of NPK fertilizer + Ivey I surfactant; (b) the addition of NPK fertilizer + Ethanol; (c) the addition of NPK fertilizer + Biorem; and (d) oxidation by Fenton’s reagent combined with NPK fertilizer. Microbial activity was evaluated following growth of heterotrophic and degrading microorganisms, dehydrogenase activity and CO2 production. Hydrocarbons degradation was established by determination of TPH, alkanes, branched alkanes, pristane and phytane by GC/MS. Our results have shown that the application of NPK fertilizer in combination with Ivey surfactant is an efficient treatment to be applied in clay soil. Treatment with Fenton’s reagent previous to the application of NPK fertilizer also efficiently enhanced hydrocarbon biodegradation in saturated conditions.

When Can Surfactants Enhance HydrocarbonBiodegradation In Oil Biotreatments

Petroleum hydrocarbon compounds bind to soil components and are difficult to remove and degrade. Surfactants and emulsifiers can emulsify hydrocarbons enhancing their water solubility, and increasing the displacement of oily substances from soil particles. The effects of the Ivey surfactant on oil hydrocarbon biodegradation was studied using microcosm systems containing three different soil types amended with commercial NPK fertilizer. Microbial activity was evaluated following growth of heterotrophic and degrading microorganisms, dehydrogenase activity and production of CO2. Hydrocarbon degradation was established by determining the amount of TPH (total petroleum hydrocarbon) and alkanes, the indices nC18/phytane and pristane/nC17 and the percentage of prystane and phytane. Ivey surfactant augmented the amount of hydrocarbon removed in both clay and sandy soil. This indicates that surfactant could play an important role as a biostimulating agent at the beginning of the process and in combination with a nutrient addition. Also, CG/SM analyses have shown changes in hydrocarbon composition related to the rate of biodegradation