Decolorization of molasses wastewater from distilleries using bacterial consortium

Abstract

Distillery effluent from sugarcane molasses leads to an environmental pollution due to its large volume and the presence of dark brown colored compounds, known as melanoidins. In this study, a bacterial consortium CONS8 isolated from waterfall sediments in Maehongsorn province was selected as a molasses-decolorizing consortium. Consortium CONS8 was able to decolorize, only within 2 days, in Erlenmeyer flasks, three different synthetic wastewaters containing either Viandox sauce (13.5% v/v), beet molasses wastewater (41.5% v/v) or sugarcane molasses wastewater (20% v/v) at 9.5, 8.0 and 17.5%, respectively. Four predominant bacteria present in the consortium CONS8 were identified by the 16S rDNA analysis. To achieve the highest decolorization, the artificial bacterial consortium MMP1 comprising Klebsiella oxytoca, Serratia mercescens (T2) and unknown bacterium DQ817737 (T4), was constructed. Under optimized conditions (aeration, pH), the bacterial consortium MMP1 was able to decolorize the synthetic melanoidins-containing wastewater at 18.3% within 2 days. The comparison of decolorization by the consortium MMP1 with abiotic control proved that the color removal for synthetic melanoidins-containing wastewater medium was mainly due to biotic activity of bacterial cells, without any adsorption phenomena. Supplement of nutrients and vitamin B did not promote melanoidins decolorization by bacterial consortium MMP1. Finally, the performance of a membrane bioreactor (MBR) for synthetic melanoidins-containing wastewater treatment was investigated at laboratory scale, with a mineral membrane. The reactor seeding was made with the MMP1 bacterial consortium inoculum. The reactor was performed with several hydraulic retention times (HRT) of 15, 20, and 40 hours. The performances were analyzed in terms of COD, color removal and biomass in the reactor. The results indicated that the higher COD and color removal efficiency were achieved with the longer HRT.