Evaluation and comparison of UV/H2O2 and adsorption on active carbon as a tertiary wastewater treatment for pharmaceutical removal within a small WWTP: a pilot study†

Pharmaceuticals and their metabolites are ubiquitous in the environment and represent typical anthropogenic micropollutants. Due to their low diffusive concentrations and often recalcitrant nature, the compounds are not completely removed by conventional biological wastewater treatment technologies, which emphasizes the need for tertiary treatment steps. This study was performed to evaluate the feasibility of photooxidation UV/H₂O₂ technology for the removal of selected pharmaceuticals (carbamazepine, diclofenac, hydrochlorothiazide, sulfamethoxazole, and tramadol) as a tertiary treatment step within the wastewater treatment plant (WWTP) process. The UV/H₂O₂ technology was compared with the more common treatment method of adsorption on granulated activated carbon (AC) in short-term and long-term tests. Both treatment systems were installed as pilot-scale units at a WWTP in a small village (equivalent of about 900 people) where a psychiatric hospital is located in the Czech Republic. The short-term tests highlighted several important aspects that need to be addressed within full-scale operations (e.g., mechanical pretreatment of wastewater, relation between H₂O₂ dose and UV dose). The initial concentration of tramadol was up to 5000 ng l⁻¹, and that of carbamazepine and hydrochlorothiazide was up to 3000 ng l⁻¹ in the WWTP outflow. The results showed that both units were capable of removing more than 95% of the pharmaceuticals during the long-term tests. As oxidation processes can generate transformation products (TPs), the ecotoxicity evaluation was addressed. Ecotoxicity using the bioluminescence bacterium Vibrio fischeri and the rainbow trout gill cell line (RTgill-W1) did not indicate any increase in ecotoxicity parameters in comparison to the inflow water samples for both units. Both processes were finally evaluated from an economical point of view, and the pilot-scale AC unit was more favorable in this context; however, estimations for a full-scale system suggest that the UV/H₂O₂ system is more economically feasible in terms of operational costs.