Efficiency and ecotoxicity of activated biochar in the treatment of artificial wastewater contaminated by pharmaceuticals

Pharmaceuticals are emerging contaminants of global concern due to potential ecotoxicity and persistence in wastewater. Since conventional wastewater treatment plants are not designed to remove micropollutants and the removal efficiency varies compound-specifically, pharmaceuticals pose a risk in the recipient aquatic environments. Adsorption by solid materials such as activated biochar has been suggested to offer a practical removal method. However, not much is known about the environmental risks of the adsorbents used in wastewater treatment. This study aimed to study the efficiency of activated biochar (ACB) to remove low and high concentration of specific pharmaceuticals including diclofenac (DI), tetracycline (TE), and cephalexin (CEP) from Milli-Q water (MQ) and artificial wastewater (AWW). Furthermore, the study evaluated the ecotoxicity of these pharmaceuticals, as well as pristine ACB and ACB loaded with pharmaceuticals (ACB-LP), in both MQ and AWW using Daphnia magna. The adsorbate concentration and matrix affected ACB's removal efficiency. Weaker adsorbent-adsorbate interactions and mass transfer resistance at lower adsorbate concentrations, along with interactions between wastewater constituents and pharmaceuticals were the leading factors contributing to this reduction. These experimental observations indicate practical considerations for using adsorbents in operational wastewater settings. Furthermore, ACB-LPs generally exhibited lower toxicity compared to ACB, attributed to the saturation of free binding sites and reduced adhesion to daphnids. This study highlights the importance of examining the environmental risks of adsorbent materials used in wastewater treatment, particularly given their anticipated future use.