Oxidation of pharmaceutically-active compounds (PhACs) during water treatment with potassium permanganate

The widespread occurrence of pharmaceutically active compounds (PhACs) in aquatic environment is raising worldwide concerns about potential adverse effects on aquatic ecology and human health. Potassium permanganate (KMnO ₄), a powerful and environmentally friendly oxidant currently used by utilities to address a range of issues, is potentially effective for oxidative removal of PhACs. This contribution reports for the first time on the oxidation of widely detected PhACs during water treatment with KMnO₄. Eighteen chemicals, covering several major classes of pharmaceuticals and wastewater-derived micropollutants, were screened for potential reactivity with permanganate. Results show that ten of the screened PhACs are either highly or moderately reactive with KMnO₄. Detailed kinetic studies were then performed for the most reactive PhACs (results from carbamazepine oxidation are described in detail in this paper) to determine basic kinetic parameters and evaluate the effects of important water quality parameters (pH, temperature) and the presence of non-target water constituents (e.g., NOM, Fe²⁺, Mn²⁺, and etc.). The removal efficiency of carbamazepine in two utility source waters treated with KMnO₄ was also tested and the results agree reasonably well with predictions from the kinetic model parameterized using experiments conducted in deionized water at much higher reagent concentrations. Several carbamazepine oxidation products were identified by liquid chromatography-tandem mass spectrometry, and the proposed structures for these intermediates confirmed an oxidation mechanism involving electrophilic attack at the non-aromatic olefinic group in the central heterocyclic ring of carbamazepine.