Removal of colored substances from molasses waste water by biological treatment systems combined with chemical treatment

In this study, we attempted to combine a biological treatment process which used Bi-Act SCBA system (SCBA) and chemical treatment process to remove chemical impurities such as COD, BOD5 and nutrients as well as colored substances from the molasses waste water (MWW). In the pilot plant experiment, SCBA unit A (SCBA-A) was used for the pre-aeration and uniformity of the MWW before biological treatment. The sludge volume (SV30) was about 50 ml/l in the aeration unit of the SCBA-A. The COD and colored substances could not be removed in this step. However, in both SCBA-B and SCBA-C, SV30 increased up to 350-400 ml/l. At the same time, approximately 44.0% and 22.9% of COD of the effluents from SCBA-B and SCBA-C were removed, respectively. On the other hand, the removal of colored substances in SCBA-B and SCBA-C (about 25.0 and 13.3%) was not appreciable. However, the colored substances in the MWW passing through SCBA-B and SCBA-C could be easily precipitated by chemical agents compared with the original MWW. About 93% of the colored substances of the effluent from SCBA-C could be removed in the chemical precipitation step, while the colored substances in the original MWW could not be precipitated.