Evaluation of pharmaceutical removal in seven WWTPs : Efficiency of different treatment technologies

Abstract: Wastewater treatment plants (WWTPs) are originally not constructed to remove pharmaceuticals from the wastewater. Biological treatment technologies used in many WWTPs today, e.g., activated sludge, MBBR and trickling filters, can, however, remove some pharmaceuticals well. Advanced treatment technologies, like ozonation, can be used as a complement to biological treatment for an even better removal. Käppala WWTP is not required to remove pharmaceuticals today, but is obligated to follow the development of advanced treatment technologies and prepare to implement one in the future. Additionally, a new wastewater treatment directive is under development with stronger regulations of pharmaceutical removal. Because of this, it is important to gather information about removal efficiencies for different treatment technologies in Käppala and other WWTPs. In this project, direct injection-UHPLC-Orbitrap-MS/MS was used to analyze wastewater from seven different WWTPs, including Käppala, with the aim to detect as many pharmaceuticals as possible. The removal efficiencies for 59 identified compounds, most of them pharmaceuticals, were used to evaluate the WWTPs and their treatment technologies. 55 of these compounds were detected in Käppala WWTP while 48 were detected in all seven WWTPs. In Käppala WWTP, around half of all compounds were removed with less than 20 %, including most of the compounds that is proposed to be regulated in the new wastewater treatment directive. This highlights the need for Käppala WWTP to introduce new treatment technologies. Two Swiss plants with ozonation had a removal efficiency > 80 % across the whole plant for 79 % and 67 % of the compounds respectively. In the WWTPs that lacked advanced treatment technologies only 12-33 % of the compounds had a removal > 80 %. One compound, chlorothiazide, did however increase 30 times across the plants with ozonation treatment. The trickling filter in one WWTP barely removed any compound with more than 20 % and was thereby the biological treatment technology with lowest removal efficiency. Activated sludge without N-removal also had a slightly lower removal of pharmaceuticals compared to activated sludge with N-removal and MBBR, possibly due to a shorter hydraulic retention time (HRT) and sludge retention time (SRT).