Methods and systems utilize an atmospheric-pressure nitrogen dielectric-barrier discharge to treat the surface of polymer substances. The atmospheric-pressure nitrogen dielectric-discharge may be maintained with a level of H2O below a pre-defined amount, such as by measuring and controlling the H2O within a treater, to produce a surface treatment for a polymer substance that yields desirable characteristics. Furthermore, the H2O level may be measured and controlled according to a pre-defined amount or according to another parameter such as an analysis of the resulting polymer surface. For example, the polymer surface may be provided with an optimal added nitrogen-to-added oxygen ratio and/or an optimal stability based on washed and unwashed advancing contact angles such as by controlling the H2O level within the treater based on these analyses of the treated polymer.