Résumé
The European Union encourages irrigation with treated wastewater by limiting monitoring to a single indicator: faecal contamination (E. Coli). Beyond the health protection of the actors, our work focused on the environment (soil plant) that sees and receives this unconventional water resource. In fact, reclaimed wastewater irrigation can cause also advert effects for soil microbiomes. Nevertheless, the positive effects of nutrients and organic matter, contained in reclaimed water, may be counterbalanced by the fluxes and loads of biotic and abiotic contaminants. The objective of this study was to evaluate the impact of irrigation with four different wastewater qualities on soil microbiome structures along two seasons of lettuce crop. The four unconventional water tested were: (1) Tap water, (2) membrane bioreactor effluent (MBR), (3) constructed wetlands (CW) and (4) raw urban wastewater (RW). These Wastewater qualities were evaluated based on their nutrient and microbiological contents. Whereas, the impacts on soils were quantified based on the modifications of content in organic matter and of microbial communities. Microbial community were quantified using high-throughput 16S rRNA gene sequencing and qPCR. A low impact of wastewater types on autochthonous microbial community fate was observed. Interestingly, microbial community structures from samples irrigated with tap water and different reclaimed wastewater level could not be distinguished. In RW, CW and MB microbial contaminants such as pseudomonas aeruginosa, E.coli and enterococci faecalis were concentrated between 102-106 , 103-107 and 102-109 DNA copies/mL respectively. However, their persistence in soil were very low and close to zero. Overall, the results show an adaptation of microbial communities to the disturbance undergone by reclaimed wastewater. In addition, these practices did not seem to drive significant risks related to pathogenic microorganisms by transfer via the soil due to their low resistance