Fluid treatment systems and compositions are provided including (a) at least one material including (1) at least one carboxylic acid functional group and (2) at least one sulfur-containing group selected from the group consisting of sulfonyl functional groups, sulfonate functional groups and mixtures thereof; and (b) at least one scale control agent. The fluid treatment systems and compositions can be used to treat aqueous systems, for example as fracturing fluids for treating aqueous compositions found in subterranean formations. Methods for inhibiting formation and/or precipitation of calcium salts in an aqueous composition using the fluid treatment systems or compositions also are provided.