How to utilize electrocoagulation (EC) technology for algae-polluted water treatment in an energy-efficient manner remains a critical challenge for its widespread application. Herein, a novel biocathode-coupled electrocoagulation cell (bio-ECC) with sacrificial iron anode and nitrifying biocathode was developed. Under different solution conductivities (233 +/- 10.25 mS cm(-1) and 4.94 +/- 0.55 mS cm(-1)), the bio-ECC achieved almost complete removal of algae cells. The maximum power densities of 8.41 and 11.33 Wm(-3) at corresponding current densities of 48.03 Am-3 and 66.26Am(-3) were obtained, with the positive energy balance of 4.52 and 7.44W m(-3). In addition, the bio-ECC exhibited excellent NH4+-N removal performance with the nitrogen removal rates of 7.28 mg L-1 h(-1) and 6.77 mg L-1 h(-1) in cathode chamber, indicating the superiority of bio-ECC in NH4+-N removal. Pyrosequencing revealed that nitrifiers including Nitrospira, Nitrobacter, Nitrosococcus, and Nitrosomonas were enriched in biocathode. The removal mechanisms of algae in anode chamber were also explored by AFM and SEM-EDX tests. These results provide a proof-of-concept study of transferring energy-intensive EC process into an energy-neutral process with high-efficiency algae removal and electricity recovery. (C) 2017 Published by Elsevier B.V.