Characteristic of Dissolved Organic Matters Removal from Bio-Treated Effluents of Textile and Dyeing Wastewater by Coagulation Enhanced with KMnO4

Abstract

In this paper, the effectiveness of coagulation enhanced with KMnO₄ for removal of dissolved organic matter from bio-effluent of textile and dyeing wastewater was investigated. Under the optimal dosing conditions, coagulation enhanced with KMnO₄ had better American Dyeing Manufactures Institute value (ADMI_7.6) and removal of dissolved organic carbon (83 % versus 72 %; 40 % versus 36 %) than magnesium sulphate coagulation alone. The results of XAD-8/XAD-4 tandem resin fractionation and molecular weight distribution measurements demonstrated that the removal of hydrophobics, transphilics and large-molecular weight organics were improved by enhanced coagulation, the ADMI_7.6 value was 40 % lower than the effluent of magnesium sulphate coagulation alone. Moreover, the hydrophilics and low-MW (< 1 K Da) organics in the effluent of enhanced coagulation were increased by 39 and 145 %, respectively, which were the main reasons for inconspicuous improvement of dissolved organic carbon removal. Qualitative analysis on dissolved organic matter with three-dimensional excitation emission matrix fluorescence spectroscopy (3-DEEMs) indicated that the colour-caused matters, fulvic-like and humic-like organics were further removed during enhanced coagulation process. Meanwhile, the increased low-molecular weight hydrophilics were protein-like and fulvic-like organics dominantly. Coagulation enhanced with KMnO₄ should be combined with additional treatment steps that specialized in removing the remained dissolved organic matter (mostly molecular weight < 1 K Da, hydrophilic) to produce a high removal performance.