Occurrence of pharmaceutical active compounds in sewage sludge from two urban wastewater treatment plants and their potential behaviour in agricultural soils

Abstract

Sewage sludge/biosolids are widely used in intensive farming to maintain fertility and enhance crop yields. Therefore, characterization of these matrices is necessary to ensure their safe use, especially regarding the presence of contaminants of emerging concern (CECs), namely pharmaceutical active compounds (PhACs). Little to no studies have ever been conducted in Portugal in this type of matrices, meaning these results may impact the way wastewater sludges are used moving forward. Accelerated solvent extraction (ASE) coupled to the solid-phase extraction (SPE), and high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was optimised for the analysis of 24 PhACs in sewage sludge samples from two Portuguese urban wastewater treatment plants (UWWTP), Beirolas and Faro. The limit of detection (LOD) and quantification (LOQ) for the PhACs ranged between 1.66 ng g⁻¹ and 10.5 ng g⁻¹ and between 5.49 ng g⁻¹ and 34.5 ng g⁻¹ in dry weight, respectively. Sixty-seven sewage sludge samples were analysed, with caffeine being the most prevalent compound, with the highest concentration measured in Beirolas and Faro of 4035 ng g⁻¹ and 129.9 ng g⁻¹, respectively. Carbamazepine, acetaminophen, diclofenac, naproxen, sulfapyridine, and propranolol were also prevalent, with a percentage of detection higher than 80%. The sewage sludges are indeed efficient in retaining PhACs, and the physico-chemical properties of PhACs and the soil must be evaluated when considering the use of sewage sludge as fertilizers in agriculture. Soils' pH is crucial to PhACs adsorption. Regarding target PhACs, only ibuprofen and sulfamethoxazole can potentially be absorbed by plants.