Distinguishing the roles of carrier and biofilm in filtering media for the removal of pharmaceutical compounds from wastewater

Pharmaceutical compounds (PCs) represent a large group of micropollutants in wastewaters (WW) worldwide. Many PCs are resistant to conventional WW treatment. Moreover, for some PCs the removal process is reversible. The aim of this study was to test three newly developed ceramic carriers for biofilm formation and PCs removal. The testing of untreated WW samples by liquid chromatography coupled to Orbitrap mass spectrometry allowed to detect the occurrence of 18 PCs in the range from 26 ng/L to 20,688 ng/L, with the highest concentrations found for caffeine. Besides, among PCs with concentrations above 1,000 ng/L, ibuprofen (19,234 ng/L), naproxen (1,405 ng/L), xylazine (1,366 ng/L), and diclofenac (1,311 ng/L) were found. Two aliquots of municipal WW were treated on laboratory scale by contacting with the filtering medium for 2 h and 7 days. The majority of PCs detected in WW were removed more effectively during the first 2 h when using filtering media coated with a previously developed biofilm derived from activated sludge. The removal of PCs from the second portion of WW by the biofilm-coated filtering media over 7 days was comparable to the results obtained over 2 h. Particular attention was paid to the reversible occurrence of some PCs in WW. Thus, a higher number of PCs with negative removal yield was observed when using filtering media without biofilm, as compared to the biofilm-coated media, namely, losartan, ketoprofen, valsartan, atorvastatin, and naproxen. However, sulfamethoxazole showed an increased concentration in WW after 7 days in contact with biofilm-coated media. An increase of diclofenac in WW after 7 days incubation was detected regardless of the presence of biofilm. One of three ceramic materials tested, i.e., oxide ceramics sintered at 1700 °C from alumina, kaolin, and silica demonstrated the best results in terms of minimizing the reversible occurrence of PCs in WW.