Abstract
A bioslurry reactor was designed and used to treat loamy clay soil polluted with polycyclic aromatic hydrocarbons (PAHs). To this end, biostimulation alone, or combined with bioaugmentation with two bacterial strains (Rhodocccus erythropolis and Pseudomonas stuzeri) previously isolated from the polluted site, was applied. The PAH concentrations decreased notably after 15 days in all of the treatments. The concentrations of the two- and three-ring compounds fell by >80%, and, remarkably, the four- to six-ring PAHs also showed a marked decrease (>70%). These results thus indicate the capacity of bioslurry treatments to improve, notably, the degradation yields obtained in a previous real-scale remediation carried out using biopiles. In this sense, the remarkable results for recalcitrant PAHs can be attributed to the increase pollutants’ bioavailability achieves in the slurry bioreactors. Regarding bioaugmentation, although treatment with R. erythropolis led to a somewhat greater reduction of lighter PAHs at 15 days, the most time-effective treatment was achieved using P. stutzeri, which led to an 84% depletion of total PAHs in only three days. The effects of microbial degradation of other organic compounds were also monitored by means of combined qualitative and quantitative gas chromatography mass spectrometry (GC–MS) tools, as was the evolution of microbial populations, which was analyzed by culture and molecular fingerprinting experiments. On the basis of our findings, bioslurry technology emerges as a rapid and operative option for the remediation of polluted sites, especially for fine soil fractions with a high load of recalcitrant pollutants.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are common pollutants produced by industrial activities, which involve the use of fossil fuels, as well as from natural events such as forest fires [1]
We examined the effectiveness to deplete contaminants and the evolution of the microbial populations involved in the biological process in three scenarios, namely: biostimulation by the autochthonous microbial community of the soil, and bioaugmentation using two degrading strains, namely Pseudomonas stutzeri and Rhodococcus erythropolis, previously isolated at the study site
The extracts were injected into a 7890A gas chromatograph (GC) System coupled to a 5975C Inert XL Mass
Summary
Polycyclic aromatic hydrocarbons (PAHs) are common pollutants produced by industrial activities (chemical and petrochemical industries, energy production, etc.), which involve the use of fossil fuels, as well as from natural events such as forest fires [1]. The main properties of PAHs vary in the function of the number of rings, and their molecular weight; for instance, the chemical reactivity, aqueous solubility, and volatility of these compounds decrease with increasing the molecular weight, Appl. Sci. 2020, 10, 2837 becoming more recalcitrant [3]. The main environmental agencies have identified 16 PAHs as priority pollutants, because they show a greater toxicity than others [4]. Some of these PAHs are toxic, mutagenic, and carcinogenic [5], and they are all highly hydrophobic and raise considerable environmental concern [6]
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