Removal of antibiotics from wastewater by adsorption and biodegradation

Antibiotics may enter the water cycle from a variety of sources, including discharges from hospitals, domestic sewage and manufacturing processes, etc.. The occurrence of these chemicals in the aquatic environment has been reported all over the world. Recently, the adverse effects of antibiotics in water on the ecosystem and on the human health have been recognized. This means that wastewater treatment plants should take special actions to treat the antibiotic-bearing wastewater. However, research focused on the removal of antibiotics is still limited. Among existing wastewater treatment technologies, adsorption and biodegradation are both extensively used for handling a wide variety of wastewaters. Therefore, this study aimed to develop a novel combined adsorption-biodegradation process for efficiently treating antibiotic-bearing wastewater, i.e. the biofilm-covered granular activated carbon (BGAC) system. In the first phase of study, adsorption of three typical β-lactam antibiotics, namely, penicillin G (PCG), ampicillin (AMP) and cephalosporin C (CPC) by granular activated carbon (GAC) was investigated. Characterization of the antibiotic-loaded GAC showed that PCG, AMP and CPC in solution would be first adsorbed in the microspores of GAC, and were further bound to the GAC functional groups. Results showed that Langmuir isotherm can provide the satisfactory prediction of the equilibrium data, and the maximum adsorption capacity (qm) at 25°C was found to be 427.3, 164.2 and 33.67 mg g-1 for PCG, AMP and CPC, respectively. These suggest that GAC is an effective adsorbent for antibiotics. In addition, the thermodynamic analysis revealed that the adsorption of these antibiotics by GAC would be of chemisorption. For almost all the adsorption study, empirical first- and second-order rate equations are commonly used without understanding their theoretical origins. In such a situation, a new transformed Langmuir kinetics was for the first time developed in this study, by which it was further shown that first- and second-order rate equations for adsorption would be special cases of Langmuir kinetics under certain conditions. A principle for simplification of Langmuir kinetics to first- or second-order rate equation was thus established. The proposed theory for adsorption kinetics was verified with the data of antibiotics adsorption by GAC as well as the literature data. To exploit a high-efficiency process for treating antibiotic-bearing wastewater, a continuous airlift bioreactor with GAC as support carrier was successfully developed. It was clearly shown that the biofilm-covered GAC, namely BGAC, had the strong capability to remove AMP present in the influent.Doctor of Philosophy (CEE