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Biotreatability evaluation

Lab-scale biotreatability experiments have been done in the 3 target contaminated soils (NB from Rouen, UNITUS from Borgo Faiti, UAM with the soil from Huelva). This action leads to the selection of the optimal pilot conditions to the best performance according to each site’s specific characteristics. This is not considered research, as this is a mandatory step that is routinely performed for the implementation of commercialised bioremediation technologies, meant to ensure a successful performance in full-scale treatment because each polluted soil has different behaviour and reactivity against TPHs, soil characteristics and microbiological profile. Biotreatability tests will thus be part of the final solution.

According to the sites’ characterization (A1), correction measures of the soil properties have been implemented for the proper development of fungi. The lignocellulosic amendment is being calibrated based on the textural and bulk density properties of the soil, increasing the loading rate in fine-grained soils. The moisture has been adjusted to 60-75% of the water holding capacity (WHC). Fertilizers have been added when the concentration and ratios of nutrients (C/N/P) did not fall within the optimal ranges.

Considering those necessary adjustments, a battery of biodegradability tests has been implemented to find the best operational parameters: fungal strain, soil/substrate ratio, soil/fungi mixture (e.g non-mixed layers disposition versus total mixing) and nutrients. 2 general approaches of fungal inoculation have been tested: a) the use of spent mushroom substrate (SMS) from the edible mushrooms A. bisporus, P. ostreatus, P. eryngii, L. edodes (UAM) and b) inoculation of pasteurized lignocellulosic residues (derived from cereal crops or sawmill wastes) with spawns from commercial suppliers of edible mushrooms (UNITUS) or from isolated environmental strains (NB).

The biotreatability tests have been performed in 1-5 L reactors. Control experiments, without fungal inoculation have been included to evaluate the TPH removal compared to conventional bioremediation. The extent of fungal colonization and persistence over time have been monitored by D-glucosamine or ergosterol contents and activity of lignin-modifying enzymes.

Selection of the best treatment combination of the variables will reduce potentially the level of uncertainty inherent in bioremediation approaches and will provide useful information for the design of remediation strategy (B1.2).