Effect of potassium permanganate dosing position on the performance of coagulation/ultrafiltration combined process

Abstract

Abstract The effects of potassium permanganate (KMnO 4 ) dosing position on the natural organic matter (NOM) removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process. KMnO 4 oxidation altered the NOM characteristics in terms of hydrophobicity and molecular weight, and destroyed humic substances originated from terraneous organisms in raw water. The optimal KMnO 4 dosage was 0.5 mg·L − 1 in the peroxidation enhanced coagulation process with respect to the dissolved organic carbon (DOC) removal. When KMnO 4 was dosed into both upstream and downstream of coagulation, namely in the proposed two-position dosing mode, coagulation and KMnO 4 oxidation worked individually on the apparent DOC removal. However, compared to the KMnO 4 addition prior to or after coagulation, the two-position dosing mode dramatically alleviated membrane fouling and reduced fouling irreversibility. This was attributed to the change of NOM characteristics as a result of KMnO 4 addition prior to coagulation and the presence of MnO 2 on membrane surface as a result of KMnO 4 addition prior to ultrafiltration. This work may provide useful information for the application of KMnO 4 oxidation in the coagulation/ultrafiltration combined system.