# Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor
###### 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 (_Rhodoccus erythropo_ 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 biopsies. 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. PAH; bioslurry; soil pollution; bioaugmentation; _Pseudomonas; Rhodococcus_ Article  
Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor  
[PERSON] 1,*  
29 March 202017 April 20  
thus 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 thus raise considerable environmental concern [6]. PAHs released into environmental compartments can be removed through processes such as volatilization, photo-oxidation, chemical oxidation, bioaccumulation, and adsorption [7]. Concretely, the remediation of polluted soils can be attained using physical-chemical and/or biological approaches. Indeed, the combination of both technologies can enhance the cleaning of PAH-contaminated soil [8]. In recent decades, the interest in biological methodologies has been growing. In fact, bioremediation can help reduce risks to ecosystems and human health from soil pollution, and effectively restore polluted sites, and they are generally considered environment-friendly treatments. bioremediation involves the removal of pollutants from a contaminated matrix, or their immobilization or transformation into less toxic products, thereby mitigating their harmful effects [9]. In this context, PAHs can be removed from environmental compartments, such as soils, through microbial transformation and degradation [10]. The microorganisms may be naturally occurring (autochthonous) in the contaminated area, or can be isolated from elsewhere and brought to the site. In the first case, the degradation of hydrocarbons or other organics can be enhanced by providing such microorganisms with nutrients, thereby stimulating their activity [11; 12] (biostimulation). In the second case, polluted soils are inoculated with microbial consortia or single isolates [11] (bioaugmentation). Bioremediation is generally performed using one or both of these approaches, depending on the soil conditions and the microbial communities of the study site.