Ion-based adsorbents - Granular ferric hydroxide (GFH) and Sorb 33 (E33) are commercially available porous adsorbents. These adsorbents are currently being used or expected to be used in a large number of full-scale arsenic treatment systems throughout the US. This study investigated the impact of silica fouling in arsenic removal using ironbased GFH and E33. Batch experiments and column experiments have been conducted to understand the role of silica in arsenic adsorption. It has been observed that adsorption of silica reduces the operational lifetime of GFH and E33 significantly through changing the surface charge. However, several operational strategies such as - (a) series column operation with delayed connection of the second column and (b) regeneration with caustic solution at pH-12 can be used to increase operational lifetime of the adsorptive packed bed system.