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Persulfate (PS)-based advanced oxidation processes (AOPs) have been promoted as alternatives to H2O2-based AOPs. To gauge the potential of this technology, the PS/Fe­(II) and Fenton (H2O2/Fe­(II)) processes were comparatively evaluated using formate as a simple target compound and nanofiltration concentrate from a municipal wastewater treatment plant as a complex suite of contaminants with the aid of kinetic modeling. In terms of the short-term rate and extent of mineralization of formate and the nanofiltration concentrate, PS/Fe­(II) is less effective due to slow Fe­(II)/Fe­(III) cycling attributable to the scavenging of superoxide by PS. However, in the concentrate treatment, PS/Fe­(II) provided a sustained removal of total organic carbon (TOC), with ∼81% removed after 7 days with SO4 •– consistently produced via homolysis of the long-life PS. In comparison, H2O2/Fe­(II) exhibited limited TOC removal over ∼57% after 10 h due to the futile consumption of H2O2 by HO•. PS/Fe­(II) also offers better performance at transforming humic-like moieties to more biodegradable compounds as a result of chlorine radicals formed by the reaction of SO4 •– with the matrix constituents present in the concentrate. The application of PS/Fe­(II) is, however, subject to the limitations of slow oxidation of organic contaminants, release of sulfate, and formation of chlorinated byproducts.