Bioremediation of aromatic hydrocarbons contaminated soil from industrial site using surface modified amino acid enhanced biosurfactant

Supramolecular bioamphiphile facilitated bioemulsification and concomitant treatment of recalcitrant hydrocarbons in petroleum refining industry oily waste

Bioremediation of real-time petroleum refining industry oily waste (PRIOW) is a major challenge due to the poor emulsification potential and oil sludge disintegration efficiency of conventional bioamphiphile molecules. The present study was focused on the design of a covalently engineered supramolecular bioamphiphile complex (SUBC) rich in hydrophobic amino acids for proficient emulsification of hydrocarbons followed by the concomitant degradation of total petroleum hydrocarbons (TPH) in PRIOW using the hydrocarbonoclastic microbial bio-formulation system. The synthesis of SUBC was carried out by pH regulated microbial biosynthesis process and the yield was obtained to be 450.8 mg/g of petroleum oil sludge. The FT-IR and XPS analyses of SUBC revealed the anchoring of hydrophilic moieties of monomeric bioamphiphilic molecules, resulting in the formation of SUBC via covalent interaction. The SUBC was found to be lipoprotein in nature. The maximum loading capacity of SUBC onto surface modified rice hull (SMRH) was achieved to be 45.25 mg/g SMRH at the optimized conditions using RSM-CCD design. The SUBC anchored SMRH was confirmed using SEM, FT-IR, XRD and TGA analyses. The adsorption isotherm models of SUBC onto SMRH were performed. The integrated approach of SUBC-SMRH and hydrocarbonoclastic microbial bio-formulation system, emulsified oil from PRIOW by 92.86 ± 2.26% within 24 h and degraded TPH by 89.25 ± 1.75% within 4 days at the optimum dosage ratio of SUBC-SMRH (0.25 g): PRIOW (1 g): mass of microbial-assisted biocarrier material (0.05 g). The TPH degradation was confirmed by SARA fractional analysis, FT-IR, ¹H NMR and GC-MS analyses. The study suggested that the application of covalently engineered SUBC has resulted in the accelerated degradation of real-time PRIOW in a very short duration without any secondary sludge generation. Thus, the SUBC integrated approach can be considered to effectively manage the hydrocarbon contaminants from petroleum refining industries under optimal conditions.

A review for recent advances on soil washing remediation technologies

Contaminated soils have caused serious harm to human health and the ecological environment due to the high toxicity of organic and inorganic pollutants, which has attracted extensive attention in recent years. Because of its low cost, simple operation and high efficiency, soil washing technology is widely used to permanently remove various pollutants in contaminated soils and is considered to be the most promising remediation technology. This review summarized the recent developments in the field of soil washing technology and discusses the application of conventional washing agents, advanced emerging washing agents, the recycling of washing effluents and the combination of soil washing and other remediation technologies. Overall, the findings provide a comprehensive understanding of soil washing technology and suggest some potential improvements from a scientific and practical point of view.

Rhamnolipid-Enhanced ZVI-Activated Sodium Persulfate Remediation of Pyrene-Contaminated Soil

In soil, polycyclic aromatic hydrocarbons (PAHs) are tightly bound to organic components, but surfactants can effectively transform them from a solid to a liquid phase. In this study, the biosurfactant rhamnolipid (RL) was selected as the eluent; shaking elution in a thermostatic oscillator improved the elution rate of pyrene, and the effects of RL concentration, temperature, and elution time on the elution effect were compared. After four repeated washings, the maximum elution rate was 75.6% at a rhamnolipid concentration of 20 g/L and a temperature of 45 °C. We found that 38 μm Zero-Valent Iron (ZVI) had a higher primary reaction rate (0.042 h^-1), with a degradation rate of 94.5% when 3 g/L ZVI was added to 21 mM Na₂S₂O₈ at 60 °C. Finally, electron paramagnetic resonance (EPR) detected DMPO-OH and DMPO-SO₄ signals, which played a major role in the degradation of pyrene. Overall, these results show that the combination of rhamnolipid elution and persulfate oxidation system effectively remediated pyrene-contaminated soil and provides some implications for the combined remediation with biosurfactants and chemical oxidation.

A review of the role of biosurfactants in the biodegradation of hydrophobic organopollutants: production, mode of action, biosynthesis and applications

The increasing influence of human activity and industrialization has adversely impacted the environment via pollution with organic contaminants, which are minimally soluble in water. These hydrophobic organopollutants may be present in sediment, water or biota and have created concern due to their toxic effects in mammals. The ability of microorganisms to degrade pollutants makes their use the most effective, inexpensive and ecofriendly method for environmental remediation. Microorganisms have the ability to produce natural surfactants (biosurfactants) that increase the bioavailability of hydrophobic organopollutants, which enables their use as carbon and energy sources. Due to microbial diversity in production, and the biodegradability, nontoxicity, stability and specific activity of the surfactants, the use of microbial surfactants has the potential to overcome problems associated with contamination by hydrophobic organopollutants.This review provides an overview of the current state of knowledge regarding microbial surfactant production, mode of action in the biodegradation of hydrophobic organopollutants and biosynthetic pathways as well as their applications using emergent strategy tools to remove organopollutants from the environment. It is also specified for the first time that biosurfactants are produced either as growth-associated products or secondary metabolites, and are produced in different amounts by a wide range of microorganisms.

Composting and its application in bioremediation of organic contaminants

This review investigates the findings of the most up-to-date literature on bioremediation via composting technology. Studies on bioremediation via composting began during the 1990s and have exponentially increased over the years. A total of 655 articles have been published since then, with 40% published in the last six years. The robustness, low cost, and easy operation of composting technology make it an attractive bioremediation strategy for organic contaminants prevalent in soils and sediment. Successful pilot-and large-scale bioremediation of organic contaminants, e.g., total petroleum hydrocarbons, plasticizers, and persistent organic pollutants (POPs) by composting, has been documented in the literature. For example, composting could remediate >90% diesel with concentrations as high as 26,315 mg kg^−a of initial composting material after 24 days. Composting has unique advantages over traditional single- and multi-strain bioaugmentation approaches, including a diverse microbial community, ease of operation, and the ability to handle higher concentrations. Bioremediation via composting depends on the diverse microbial community; thus, key parameters, including nutrients (C/N ratio = 25–30), moisture (55–65%), and oxygen content (O₂ > 10%) should be optimized for successful bioremediation. This review will provide bioremediation and composting researchers with the most recent finding in the field and stimulate new research ideas.