Résumé
Utilizing wastewater irrigation in agricultural practices offers the dual benefit of reducing water consumption while enriching soils with nutrients. However, this practice also presents inherent risks due to the presence of emerging contaminants. Moreover, the formation of potentially hazardous transformation products within the soil and rhizosphere, which may subsequently be absorbed by plants, further exacerbates concerns.Constructed wetlands are nature-based solutions (NBS) that can effectively provide treated wastewater for irrigation with varying nutrient contents to meet the specific requirements of different crops, thereby promoting sustainable agricultural practices. However, micropollutants are often not completely removed. Intensification of CWs with continuous or intermittent active aeration has been successfully implemented at the expense of higher capital and operational costs. In this context, bioaugmentation emerges as a promising strategy to enhance wetland treatment efficacy, leveraging the natural mycorrhization in wetlands and the pivotal role of bacteria in contaminant degradation processes.Here, we present the results of our studies using commercially available products containing spores of symbiotic fungi for enhancing the biodegradation of micropollutants in agricultural soils irrigated with treated wastewater. Two different strains belonging to Trichoderma genus were used as bioinoculants in CWs for wastewater treatment and directly in agricultural soils irrigated with wastewater.Trichoderma asperellum (strain T34) was tested for the removal of contaminants of emerging concern (CECs) and antibiotic resistance genes (ARGs) in a pilot-scale partially saturated vertical flow constructed wetland. The pilot was located outdoors at the facilities of the experimental platform for wastewater reuse in irrigation in Murviel-Lès-Montpellier (Southern France). The system was operated as tertiary treatment and was fed with real secondary treated domestic wastewater obtained by an aerated CW with a nominal treatment capacity of 3000 Inhabitant Equivalent and with additional treatment for phosphorus removal by precipitation with ferric chloride. Advanced methodologies including nontarget liquid chromatography high-resolution mass spectrometry and SmartChip™ Real-Time PCR were employed. Successful bioaugmentation was achieved, with Trichoderma exhibiting growth in competitive conditions using secondary treated domestic wastewater. Removal efficiency (RE) showed a clear correlation with compound biodegradability and sorption capacity, with easily biodegradable compounds showing higher elimination rates. Compounds with optimal plant uptake demonstrated significant removal efficiency. Notably, benzotriazole and diclofenac showed the mostbeneficial effects. Polar compounds like melamine proved most challenging to eliminate. However, high variability in removal efficiency over the experiment's duration limited treatment performance assessment. Transformation products (TPs), including N-oxide TPs and 14-hydroxyclarithromycin, were identified, with some undergoing partial elimination. Bioaugmented treatments led to a shift in ARG composition, though average removal rates remained statistically unchanged.In a second study, we explored the impact of the fungus Trichoderma harzianum on the distribution of two emerging contaminants, carbamazepine and climbazole, and their primary transformation products (TPs) in soils and lettuce tissues under controlled conditions. Physiological effects are examined by quantifying phytohormones in roots and leaves. While inoculation with Trichoderma harzianum did not notably influence the uptake of parent compounds, it did elevate TP concentrations in soil while reducing them in plant leaves after three weeks. Fungal inoculation also led to improved biomass and altered levels of certain phytohormones implicated in defense mechanisms and microbiome recruitment in roots and soils.Our findings offer valuable insights applicable to sustainable NBS-based wastewater treatment and crop cultivation, particularly in the context of reclaimed wastewater irrigation, leveraging accessible biological products for enhanced management practices.