Optimization, validation and application of a novel multiresidue method for prioritization of contaminants of emerging concern in biosolids

Abstract

Biosolids generated during municipal wastewater treatment are a source of organic matter and essential macronutrients, making them valuable to increase the fertility of soils. However, they also contain variable concentrations of micropollutants, particularly pharmaceuticals, which can pose environmental risks. An analytical methodology based on QuEChERS extraction and LC-MS/MS analysis was optimized and applied to the determination of 59 micropollutants, with large variations in their polarities and different uses, in biosolids from sewage treatment plants (STPs). Extraction efficiencies above 80%, and moderate variations in the efficiency of electrospray ionization were achieved for most of the target analytes in biosolids from different STPs. The accuracy of the final method ranged from 80% to 120% for 57 out of 59 micropollutants, with limits of quantification between 1 and 5 ng g−1, except for chlorhexidine (50 ng g−1). Forty-nine pollutants showed detection frequencies above 70%, with thirty-six compounds quantified in 100% of biosolids from 27 STPs. Biocides and psychiatric drugs represented more than 75% of residues in biosolids, with average accumulated concentrations of 5149 and 2425 ng g−1 (dry weight, d.w.), respectively. Within the first group, the maximum concentrations of azithromycin and chlorhexidine stayed above 2300 ng g−1 and 11,000 ng g−1 d.w., respectively. Ecological risk assessment of biosolids-amended soils identified fifteen compounds whose potential leaching into aquatic environments warrants further investigation. Significative accumulation in biosolids of several pharmaceuticals listed in the Wastewater Directive must be considered together, with their residues in raw and treated wastewaters, to estimate their real removal at STPs.