Anaerobic Treatability of Cane Molasses Based Bio-Ethanol Distillery Wastewater Mixed with Cane Sugar Mill Wastewater by Two Phase Multi-Stage Upflow Anaerobic Sludge Blanket Reactor

In a period of 1 year, the volumetric ratio of wastewater from a cane molasses-based bio-ethanol distillery plant (CMBP) and a cane sugar mill (CSM) was monitored and shown to be 1:2. In order to evaluate the validity of mixing the two wastewaters, their biodegradability and methanogenic activity (MA) were measured under a fixed temperature of 35°C and fixed FM ratio of 0.5 (i.e., 2 g COD/l for test substrate per 4 g VSS/l for test sludge). The results showed that the mixed wastewater was 4 % higher in biodegradability and 1.2 times higher in MA when compared with pure CMBP wastewater. Based on 100% COD input, 46% COD from the mixed wastewater was converted to methane. The MA of the mixed wastewater was 0.0006 g COD-CH4/gVSS.d. Additionally, a lab scale, 2-phase, multi-stage up-flow anaerobic sludge blanket (MS-UASB) reactor was operated at room temperature (22 to 32°C) and fed with CMBP wastewater and with mixed wastewater to investigate anaerobic treatability. Influent COD concentration and hydraulic retention time (HRT) were fixed at 15 g/l and 36 hours, respectively. The treatment process consisted of a conventional UASB reactor with a liquid volume of 24 l for the first phase of sulfate reduction, in addition to acidification by keeping influent pH at 6.0, followed by an MS-UASB reactor with a liquid volume of 12.7 l. Feeding of the wastewater mixture resulted in a sufficient level of COD removal, with an efficiency of 66.8%, higher than CMBP wastewater treatment by 10.6%.