This study investigates the importance of the organic matter characteristics of several organic amendments (i.e., buffalo manure, food and kitchen waste, fruit and vegetables waste, and activated sewage sludge) and their influence in the bioremediation of a polycyclic aromatic hydrocarbons (PAH)-contaminated soil. The removal of low molecular weights (LMW) and high molecular weights (HMW) PAHs was monitored in four bioremediation reactors and used as an indicator of the role of organic amendments in contaminant removal. The total initial concentration of LMW PAHs was 234 mg kg(-1) soil (dry weight), while the amount for HMW PAHs was 422 mg kg(-1) soil (dry weight). Monitoring of operational parameters and chemical analysis was performed during 20 weeks. The concentrations of LMW PAH residues in soil were significantly lower in reactors that displayed a mesophilic phase, i.e., 11 and 15 %, compared to reactors that displayed a thermophilic phase, i.e., 29 and 31 %. Residual HMW PAHs were up to five times higher compared to residual LMW PAHs, depending on the reactor. This demonstrated that the amount of added organic matter and macronutrients such as nitrogen and phosphorus, the biochemical organic compound classes (mostly soluble fraction and proteins), and the operational temperature are important factors affecting the overall efficiency of bioremediation. On that basis, this study shows that characterization of biochemical families could contribute to a better understanding of the effects of organic amendments and clarify their different efficiency during a bioremediation process of PAH-contaminated soil.

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The removal of polycyclic aromatic hydrocarbons (PAHs) from a naturally co-contaminated soil by PAHs and heavy metals with an initial concentration of 620 mg of total PAHs kg dry soil was investigated. The efficiency of landfarming in removing phenanthrene, pyrene, benzo(a)pyrene and the group of total 16 US EPA PAHs was evaluated. The process was biostimulated by adding centrifuged activated sewage sludge (SS) as an organic amendment. The tested ratios of contaminated soil to SS were 1:2, 1:1, 1:0.5 and 1:0 as wet weight basis. The process performance was monitored through chemical, microbiological and ecotoxicological analyses during 105 days of incubation. The results of analyses demonstrated that the treatment without centrifuged SS achieved a significantly higher total 16 US EPA PAH removal efficiency (i.e. 32%) compared to treatments with amendment. In the same treatment, the removal efficiency of the PAH bioavailable fraction was 100% for phenanthrene, benzo(a)pyrene and the group of total 16 US EPA PAHs, whereas 76% for pyrene. Ecotoxicity test performed with bioluminescent bacteria Vibrio fischeri confirmed the effectiveness of landfarming. Finally, the results showed that indigenous microorganisms under certain and controlled operating conditions have greater potential for PAH biodegradation compared to allochthonous microorganisms.