This paper reports the effect of several competing anions on arsenate adsorption with maghemite nanoparticles. Sulphate (as SO4), nitrate (as NO3-N), phosphate (as PO4-P) ions and silicate (as SiO2) were studied in dual solution with arsenate. Moreover, the combined effect of ions and other water characteristics were examined with a natural groundwater sample which was spiked with a certain amount of arsenate. Arsenate batch adsorption experiments were carried out with two different kinds of maghemite-a commercially available one and a home-made one using the sol-gel process. Sulphate (<= 250 mg.L-1) and nitrate (<= 12 mg.L-1) had a negligible effect on the arsenate (0.5 mg.L-1) adsorption at pH 3. However, both phosphate (<= 2.9 mg.L-1) and silicate (<= 50 mg.L-1) had an adverse impact on arsenate (<= 3 mg.L-1) adsorption at pH 7. Phosphate (<= 1.5 mg.L-1) showed minimal competition with arsenate (0.5 mg.L-1), while silicate (<= 10 mg.L-1) inhibition was insignificant for all studied As(V) concentrations at pH 3. The removal of arsenate from the groundwater sample was as efficient as from laboratory water for 0.5 mg.L-1 As(V) both at pH 3 and pH 7.