Occurrence of multiclass UV filters in treated sewage sludge from wastewater treatment plants

Many substances related to human activities end up in wastewater and accumulate in sewage sludge. So far, there is only one extensive survey on the occurrence of UV filter residues in sewage sludge. However, more data are required to draw a reliable picture of the fate and effects of these compounds in the environment. This study attempts to fill this gap through the determination of selected UV filters and derivatives namely 4-methylbenzylidenecamphor, benzophenone-3, octocrylene, ethylhexylmethoxycinnamate, ethylhexyldimethyl PABA, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, and 4,4′-dihydroxybenzophenone in treated sewage sludge.The target compounds were extracted using pressurized liquid extraction and after this, determined by ultra high resolution liquid chromatography-tandem mass spectrometry. The determination was fast and sensitive, affording limits of detection lower than 19 ng g⁻¹ dry weight (dw) except for 2,4-dihydroxybenzophenone (60 ng g⁻¹ dw). Good recovery rates, especially given the high complexity of sludge matrix (between 70% and 102% except for 2,4-dihydroxybenzophenone (30%)) were achieved.The application of developed method allowed reporting for the first time the occurrence of two major degradation products of benzophenone-3 that have estrogenic activity in sewage sludge: 4,4′-dihydroxybenzophenone (in 5/15 WWTPs) and 4-hydroxybenzophenone (in 1/15 WWTPs). Results revealed the presence of UV filters in 15 wastewater treatment plants in Catalonia (Spain) at concentrations ranging from 0.04 to 9.17 μg g⁻¹ dw.