Arsenic removal was employed by combining the processes of magnetic seeding flocculation and open or high gradient superconducting magnetic separation (OGMS or HGMS). The effect of magnetic seeding flocculation on arsenic removal by OGMS or HGMS was systematically investigated. Magnetite (Fe3O4) was used as magnetic seeding material and polymeric ferric sulfate (PFS) was added for combining the arsenic with the magnetite. The combination of PFS and magnetite was significant effect on arsenic removal. Magnetite or PFS dosages, magnetic seeding time and coagulant aids are the main factors in magnetic seeding process. In OGMS, arsenic removal efficiency increased from 72.5% to 90.9% when magnetite dosages increased from 25 to 300 mg/l. After magnetic seeding time increased from 0 to 15 min, arsenic removal efficiency increased from 80.0% to 94.5%, 84.5% to 97.1% or 87.0% to 98.7% after 50.75, 72.5 or 108.75 mg/l PFS added, respectively. In HGMS, the application of cationic polyacrylamide (CPA) improved the arsenic removal capacity approximately 15% when certain arsenic removal efficiency was maintained. The grain size distribution, structure and zeta potential of flocs were studied to provide a complete picture of magnetic seeding flocculation process. (C) 2010 Published by Elsevier B.V.