Arsenic is a ubiquitous toxic metalloid in the soil with both natural and anthropogenic sources. Adsorption/desorption reactions are quite possibly the most significant mechanisms influencing the mobility of arsenic in soils, and, hence, are critically important knowledge for effective implementation of appropriate remedial strategies for arsenic-contaminated aqueous systems. Amorphous Fe/Al-oxides typically play a dominant role in providing the reactive surfaces for arsenic adsorption. The majority of the water treatment residuals (WTRs) generated in the United States contain considerable amounts of amorphous Fe- and Al-oxides. The WTRs can be classified as waste byproducts from drinking water treatment facilities and are generally composed of Fe/Al-oxides, activated C, and high molecular weight, long-chain polymers. The reported study investigated the potential of Al- and Fe-WTRs to adsorb arsenic from sodium arsenate solutions. The extent of desorption of pre-adsorbed arsenic from the WTRs was also studied. Preliminary batch experiments identified the optimal equilibration time and solid/solution ratio for arsenic adsorption as 24h and 1:5, respectively. Both Freundlich and Langmuir adsorption isotherm models were fit to the experimental data; however the regression constants (>0.95, significant at p<0.001) demonstrated that the Freundlich model provided better fit to the experimental data. Following adsorption, arsenic desorption was induced using 7500 mg/kg phosphate. A significant amount of arsenic (>99%) remained bound to the WTRs even though the phosphate load was equal to the maximum initial arsenic load (7500 mg/kg). This indicates that adsorption of arsenic on the WTRs is typically irreversible and, hence, the WTRs are good prospects for in-situ arsenic fixation in soils. Moreover, incubation studies were conducted using Immokalee series soils with minimal arsenic retention capacity natively to assess the effects of soil amendment with WTRs on arsenic retention. Treating the Immokalee soil with Fe- and Al-WTRs substantially increased their arsenic sorbing capacity compared to the untreated soil.