Reduction of Wastewater Discharge toward Second-Generation Acetone-Butanol-Ethanol Production: Broth Recycling by the Fermentation-Pervaporation Hybrid Process

To reduce the butanol fermentation wastewater (BFW) discharge and to address the difficulties in BFW treatment, a novel fermentation-pervaporation hybrid process was performed. After each batch of acetone-butanol-ethanol (ABE) fermentation, ABE in the fermentation broth was ex situ separated by pervaporation. The retentate was used as the buffer and the solution for the following batches of enzymatic hydrolysis and fermentation, respectively. Results showed that there were little negative influences of the phenols and acid inhibitors on the fermentation performances using the recycled BFW. Benefits from the process for BFW discharge reduction were obvious. After 4 cycles of BFW, similar to 86% of the BFW was saved. Over 94% of ABE with concentrations of 42.5-50.2 g/L was recovered by pervaporation. Therefore, the novel process can effectively eliminate the disadvantage of large BFW discharge in the ABE fermentation processes.