The present research applied an alga-activated sludge combined system as a novel treatment to remove cephalosporins. First of all, the removal efficiency and characteristic of the common freshwater green alga Chlorella pyrenoidosa on cephalosporins were evaluated. The total removal rates for cefradine, cefalexin, ceftazidime and cefixime arrived up to 89.9%, 94.9%, 89.7% and 100%, respectively. On the other hand, the green alga had a satisfactory growth ability with the enlarged algal cell size during the whole treatment process. Finally, the removal efficiency of the alga-activated sludge combined system was evaluated. Due to the impact of the antibiotic, the removal rate of the individual activated sludge treatment was lower than 23.0%. 46.3% of the antibiotic were removed by the acclimated activated sludge after a two-week adaptation. However, a high total removal rate (97.91%) was obtained based on the combined system. It indicated that the green alga performed an excellent removal capacity for cefradine in the first treatment process. The activation of the alga also improved the removal efficiency of the subsequent activated sludge treatment process without acclimation. Compared with the traditional biological treatment, the combined treatment system could use the un-acclimated activated sludge directly and finally obtain high removal efficiency. (C) 2014 Elsevier B.V. All rights reserved.