Characterization of persistent colors and decolorization of effluent from biologically treated cellulosic ethanol production wastewater

The high chroma of cellulosic ethanol production wastewater poses a serious environmental concern; however, color-causing compounds are still not fully clear. The characteristics of the color compounds and decolorization of biologically treated effluent by electro-catalytic oxidation were investigated in this study. Excitation-emission matrix (EEM), fourier transform infrared spectrometer (FTIR), UV-Vis spectra, and ultrafiltration (UF) fractionation were used to analyze color compounds. High chroma of wastewater largely comes from humic materials, which exhibited great fluorescence proportion (67.1 %) in the biologically treated effluent. Additionally, the color compounds were mainly distributed in the molecular weight fractions with 3-10 and 10-30 kDa, which contributed 53.5 and 34.6 % of the wastewater color, respectively. Further decolorization of biologically treated effluent by electro-catalytic oxidation was investigated, and 98.3 % of color removal accompanied with 97.3 % reduction of humic acid-like matter was achieved after 180 min. The results presented herein will facilitate the development of a well decolorization for cellulosic ethanol production wastewater and better understanding of the biological fermentation.