Simultaneous removal of sulfamethoxazole, 17β-estradiol, and carbamazepine from hospital wastewater using a combination of a continuous constructed wetland-based system followed by photocatalytic reactor

Abstract

Pharmaceutically active compounds (PhACs), such as sulfamethoxazole, 17β-estradiol, and carbamazepine, are ubiquitous in hospital effluent and are resistant to conventional treatment methods. Advanced oxidation techniques like photocatalysis can degrade these compounds, but their performance in continuous mode and real wastewater matrix is inadequate. Hence, this study uses an iron-modified aluminum-doped ZnO (Al-ZnO/Fe) photocatalyst to degrade sulfamethoxazole, carbamazepine, and 17β-estradiol simultaneously. Batch studies indicated that at pH 8 and 0.5 g/L of photocatalyst, removal efficiencies of sulfamethoxazole, 17β-estradiol, and carbamazepine were 98.93 ± 0.27%, 98.28 ± 0.35%, and 98.31 ± 0.57%, respectively. The toxicity of the intermediate products formed and potential application of the spent photocatalyst was also studied. However, removal of PhACs was decreased when the conditions were replicated in the continuous mode. Moreover, their removal in tap water and real hospital wastewater was further reduced. The presence of inhibiting agents in real wastewater attributed to the decrease in PhACs removal. In this context, a continuous baffled horizontal flow subsurface constructed wetland-based system followed by the photocatalytic reactor was used to treat hospital wastewater spiked with sulfamethoxazole, 17β-estradiol, and carbamazepine, and the removal efficiencies were found to be 97.16 ± 1.85%, 98.09 ± 0.92%, and 96.02 ± 2.27%, respectively.