Arsenic in drinking water affects millions globally causing skin disease and cancers of the liver, stomach, and bladder. Large-scale treatment removes arsenic effectively; however, community- and home-scale treatments are typically less effective, more costly, or labor intensive. Nanomagnetite would enable effective, economical arsenic removal in low maintenance, household sand filters. Adsorption isotherms were used to display the As(V) capacity of nanomagnetite in a variety of natural waters and pH conditions. Column design and operating conditions were assessed for optimal removal. Breakthrough was most affected by nanomagnetite percentage, residence time, inlet concentration, and nanomagnetite aggregate size. NH4OH regenerated the nanomagnetite, allowing for repeated use. No detectable nanomagnetite escaped the column; however, permanent magnets were shown to capture >98% of nanomagnetite aggregates from a fluid stream. A case study proposes the use of nanomagnetite to treat arsenic contaminated groundwater in Guanajuato, Mexico to below the Mexican EPA drinking water standard for $0.23/m3.