Untargeted metabolomic analysis to explore the impact of soil amendments in a non-conventional wastewater treatment

As non-conventional wastewater treatment, vegetation filters make the most of the natural attenuation processes that occur in soil to remove contaminants, while providing several environmental benefits. However, this practice may introduce contaminants of emerging concern (CECs) and their transformation products (TPs) into the environment. A potential improvement to the system was tested using column experiments containing soil (S) and soil amended with woodchips (SW) or biochar (SB) irrigated with synthetic wastewater that included 11 selected CECs. This study evaluated: i) known CECs attenuation and ii) unknown metabolites formation. Known CECs attenuation was assessed by total mass balance by considering both water and soil media. An untargeted metabolomic strategy was developed to assess the formation of unknown metabolites and to identify them in water samples. The results indicated that SB enhanced CECs attenuation and led to the formation of fewer metabolites. Sorption and biodegradation pro-cesses were favored by the bigger surface area of particles in SB column, especially for compounds with negative charges. Incorporating woodchips into soil shortened retention times in the column, which reduced attenuation phe-nomena and resulted in the formation of significantly more metabolites. Incomplete biodegradation reactions, fostered by shorter retention times in SW column could mainly explain these results.

Automated summary

Vegetation filters use natural attenuation processes in soil to remove contaminants from wastewater and provide environmental benefits. However, this practice may introduce emerging contaminants into the environment. This study tested the use of woodchips and biochar in column experiments to improve the system, and found that biochar enhanced contaminant attenuation and resulted in fewer metabolites, while woodchips reduced attenuation and led to more metabolites, likely due to shorter retention times.