Reducing disinfection byproduct precursors through coagulation enhancement as particle weight and size control using potassium permanganate.

The widespread use of chlorine pre-oxidation in water purification has been limited in several countries owing to the production of carcinogenic byproducts when combined with naturally occurring organic matter. This study investigates the efficient use of potassium permanganate (KMnO ₄ ) pretreatment and coagulation enhancement as particle size and molecular weight distribution controlling parameters. KMnO ₄ pretreatment significantly reduced the apparent molecular weight of humic acid due to KMnO ₄ reduction and the continuous generation of manganese dioxide (MnO ₂ ) formed in situ under neutral and alkaline conditions. The MnO ₂ formed in situ had adsorption characteristics that enabled it to form large and stable flocs with the hydrolysis products of aluminum sulfate. However, under acidic conditions, KMnO ₄ pretreatment exhibited strong oxidation characteristics due to Mn(VII) reduction to Mn(II), and the mean particle floc size was the same as without KMnO ₄ pretreatment. Overall, KMnO ₄ pretreatment is a useful alternative strategy for traditional pre-oxidation using chlorine and a good coagulant enhancement agent in neutral and basic media.