Chemical analysis of soil polluting lubricant oils prior to design a soil rehabilitation procedure

Excessive consumption of petroleum products carries the risk that these toxic chemicals enter and accumulate in the environment hazarding natural habitats or human health. Areas being close to vehicle traffic or where handling and maintenance operations of vehicles take place are considered to be particularly vulnerable, thus, we aimed at investigating a railway marshalling yard polluted by used lubricant oils (ULOs). Quantitative determination of total petrol hydrocarbons in the polluted soil revealed a high level of pollution. Apart from the presence of open-chain or branched paraffins and aromatics, Fourier transform infrared spectroscopy identified intermediers from the microbial degradative pathways of hydrocarbons. Occurence of metabolically active microorganisms even in this highly ULOcontaminated soil indicates that biological rehabilitation techniques can be preferable over more invasive and expensive physico-chemical methods to meet the soil standard

Alterations in soil fertility after used lubricating oil bioremediation

Regardless of the outcome of any environmental rehabilitation technique applied, subsequent monitoring is indispensable to assess information about soil toxicity after the treatment. Various bioremediation methods (natural attenuation, biostimulation, bioaugmentation and the usage of an organic additive) were previously performed to decontaminate soil samples taken from a railway station area polluted with used lubricating oils. In this study, ecotoxicological responses revealed that seed germination and primary root length of Indian mustard (Brassica juncea) were decreased in each remediated soil presumably by inhibiting breakdown products due to the biodegradation of used lubricants, while viability of root tips increased significantly indicating more vital mustard seedlings grown in remediated soils

Challenges of unculturable bacteria

Environmental biotechnology offers several promising techniques for the rehabilitation of polluted environments. The modern industrialized world presents novel challenges to the environmental sciences, requiring a constant development and deepening of knowledge to enable the characterization of novel pollutants and a better understanding of the bioremediation strategies as well as their limiting factors. The success of bioremediation depends heavily on the survival and activities of indigenous microbial communities and their interaction with introduced microorganisms. The majority of natural microbiomes remain uncultivated; therefore, further investigations focusing on their intrinsic functions in ecosystems are needed. In this review, we aimed to provide (a) a comprehensive overview of the presence of viable but nonculturable bacteria and yet-to-be-cultivated cells in nature and their diverse awakening strategies in response to, among other factors, signalling extracellular metabolites (autoinducers, resuscitation promoting factors, and siderophores); (b) an outline of the trends in isolating unculturable bacteria; and (c) the potential applications of these hidden players in rehabilitation processes

Intensification of Ex Situ Bioremediation of Soils Polluted with Used Lubricant Oils

Used lubricant oils (ULOs) strongly bind to soil particles and cause persistent pollution. In this study, soil microcosm experiments were conducted to model the ex situ bioremediation of a long term ULO-polluted area. Biostimulation and various inoculation levels of bioaugmentation were applied to determine the efficacy of total petrol hydrocarbon (TPH) removal. ULO-contaminated soil microcosms were monitored for microbial respiration, colony-forming units (CFUs) and TPH bioconversion. Biostimulation with inorganic nutrients was responsible for 22% of ULO removal after 40 days. Bioaugmentation using two hydrocarbon-degrader strains: Rhodococcus quingshengii KAG C and Rhodococcus erythropolis PR4 at a small inoculum size (107 CFUs g−1 soil), reduced initial TPH concentration by 24% and 29%, respectively; the application of a higher inoculum size (109 CFUs g−1 soil) led to 41% and 32% bioconversion, respectively. After 20 days, all augmented CFUs decreased to the same level as measured in the biostimulated cases, substantiating the challenge for the newly introduced hydrocarbon-degrading strains to cope with environmental stressors. Our results not only highlight that an increased number of degrader cells does not always correlate with enhanced TPH bioconversion, but they also indicate that biostimulation might be an economical solution to promote ULO biodegradation in long term contaminated soils