Drinking water treatment residuals (WTRs), an iron-rich byproduct generated during potable water production, is a potential resource with utilizable value. In this study, with WTRs as potential iron source and catalyst support, a novel CoFe2O4@WTRs hybrid was fabricated via a modified chemical co-precipitation combined with calcination method and employed as high-efficient peroxymonosulfate (PMS) activator for the degradation of atrazine (ATZ). CoFe2O4 was successfully synthesized and well dispersed onto WTRs. CoFe2O4@WTRs exhibited superior catalytic reactivity towards PMS and 98.2% of ATZ degradation was achieved with 0.03 g L2(-1) CoFe2O4@WTRs, 0.20mM PMS, and 10 mu M ATZ at initial pH 4.01. The catalytic performance of CoFe2O4@WTRs was evaluated with respect to various stoichiometric Co/Fe ratio, catalyst dosage, PMS concentration, and initial pH. Sulfate radical (SO4.-), generated through cobalt-mediated heterogeneous and homogeneous activation reactions, dominated ATZ degradation in the CoFe2O4@WTRs/PMS system. The underlying activation mechanism was elaborated based on radical species determination and X-ray photoelectron spectroscopy (XPS) observations. The intermediates of ATZ were identified by LC-MS with three main degradation pathways proposed, including dealkylation, dechlorination-hydroxylation, and deamination-hydroxylation. Finally, CoFe2O4@WTRs showed good application prospect in the remediation of ATZ contaminated real water under acidic condition.