Quantitative Non-targeted Screening to Profile Micropollutants in Sewage Sludge Used for Agricultural Field Amendments

A considerable number of micropollutants from human activities
enter the wastewater network for removal. However, at the wastewater
treatment plant (WWTP), some proportion of these compounds is retained
in the sewage sludge (biosolids), and due to its high content of nutrients,
sludge is widely applied as an agricultural fertilizer and becomes
a means for the micropollutants to be introduced to the environment.
Accordingly,
a holistic semiquantitative nontarget screening was performed on sewage
sludges from five different WWTPs using nanoflow liquid chromatography
coupled to high-resolution Orbitrap mass spectrometry. Sixty-one inorganic
elements were measured using inductively coupled plasma mass spectrometry.
Across all sludges, the nontarget analysis workflow annotated >21,000
features with chemical structures, and after strict prioritization
and filtering, 120 organic micropollutants with diverse chemical structures
and applications such as pharmaceuticals, pesticides, flame retardants,
and industrial and natural compounds were identified. None of the
tested sludges were free from organic micropollutants. Pharmaceuticals
contributed the largest share followed by pesticides and natural products.
The predicted concentration of identified contaminants ranged between
0.2 and 10,881 ng/g dry matter. Through quantitative nontarget analysis,
this study comprehensively demonstrated the occurrence of cocktails
of micropollutants in sewage sludges.