Pharmaceuticals in processing of municipal sewage sludge studied by grab and passive sampling

Abstract

Abstract Concentrations of pharmaceuticals, consisting of four anti-inflammatory and one antiepileptic drug, were studied in the aqueous and solid phase of municipal sewage sludge, collected from a wastewater treatment plant (WWTP) in central Finland. The samples included untreated municipal sludge from the biological wastewater treatment, digested sludge and sludge before and after composting. First, samples were taken as grab samples to study the bioavailable part in aqueous phase but also the part in solid fraction. Later, the long-term concentrations were studied by passive sampling with styrene divinylbenzene-reverse phase sulfonated (SDB-RPS) disks. In the untreated solid sludge, the concentrations of carbamazepine, diclofenac, ibuprofen, ketoprofen, and naproxen were 0.5 ng g−1, 26 ng g−1, 29 ng g−1, 250 ng g−1, and 13 ng g−1, while in liquid phase they were 5.6 ng L−1, 200 ng L−1, 210 ng L−1, 35 ng L−1, and 55 ng L−1, respectively. Concentrations decreased with the treatment steps but substantial amounts still occured even after the final stage. The results show that current sludge treatment cannot fully remove pharmaceuticals, leaving varying concentrations after each stage. Additionally, the results suggest that SDB-RPS disks are suitable for sampling and quantification of the bioavailable fraction of pharmaceuticals in municipal sludge.