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The high hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor for the remediation of soils and aquifers. Surfactants are amphiphilic substances which encourage the transfer of hydrophobic compounds from the solid to the liquid phase. While the interaction between organic matter and surfactants has been widely studied, there is a lack of knowledge concerning the relationship between surfactant efficiency and the granulometry of soil and/or geologic material. In this paper, three non-ionic surfactants (Tween 80, Gold Crew, and BS-400) were used to study the desorption of pyrene, chosen as a representative PAH, in soils with different grain size proportions (1%, 5%, 10%, and 20% of clay and silt) and no organic matter (<0.1%). The best quantity of surfactant to apply is closely related to the proportion of fine materials. Tween 80 gave better maximum desorption than Gold Crew and BS-400 (89%, 40%, and 36%, respectively). As an important proportion of aquifers show fine material above 1%, the effective critical micellar concentration obtained when applying surfactants to this type of geologic materials has to be higher than 150 mg L for Tween 80, and higher than 65 mg L, and 100 mg L for Golf Crew and BS 400, respectively. Furthermore, results indicate that carrying out simple laboratory tests before the use of surfactants on a field scale is necessary to improve the efficiency and minimize the financial and environmental impact of its application. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of several polycyclic aromatic hydrocarbons (PAHs) in soil through composting was investigated. The selected PAHs included: fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, and chrysene, with concentrations simulating a real creosote sample. The degradation of PAHs (initial concentration 1 g of total PAHs kg−1 dry soil) was assessed applying bioaugmentation with the white-rot fungi Trametes versicolor and biostimulation using compost of the source-selected organic fraction of municipal solid waste (OFMSW) and rabbit food as organic co-substrates. The process performance during 30 days of incubation was evaluated through different analyses including: dynamic respiration index (DRI), cumulative oxygen consumption during 5 days (AT5), enzymatic activity, and fungal biomass. These analyses demonstrated that the introduced T. versicolor did not significantly enhance the degradation of PAHs. However, biostimulation was able to improve the PAHs degradation: 89% of the total PAHs were degraded by the end of the composting period (30 days) compared to the only 29.5% that was achieved by the soil indigenous microorganisms without any co-substrate (control, not amended). Indeed, the results showed that stable compost from the OFMSW has a greater potential to enhance the degradation of PAHs compared to non-stable co-substrates such as rabbit food. [Copyright &y& Elsevier]

Abstract: The feasibility of using different organic amendments of different origin and properties in the bioremediation of pyrene-contaminated soil by means of composting has been tested. The selected pyrene concentration was 1g of pyrene per kg of dry soil. The organic amendments used include: raw organic fraction of municipal solid wastes (OFMSW), industrial compost from OFMSW composting (COFMSW), compost derived from home composting of OFMSW (HCOFMSW), anaerobically digested sludge (ADS), non-digested activated sludge (NDS) and centrifuged non-digested activated sludge (CNDS). The degradation rate was related to the amendment properties that directly affected the composting process. Raw OFMSW was not capable to enhance pyrene degradation in comparison to control, but stable HCOFMSW exhibited the highest removal rate (69%). The amendments stability and the temperatures reached as a consequence influenced the process, and thermophilic temperatures showed an inhibition effect on the microbial activity related to pyrene degradation. Some of the tested wastes need to be further investigated to find inexpensive organic amendments for soil bioremediation. [Copyright &y& Elsevier]