Reduction wastewater discharge in second-generation acetone-butanol-ethanol (ABE) fermentation process by adsorptive removal of organic acids toward the broth recycling system

The treatment of high chemical oxygen demand (COD) organic wastewater is one of the major technical bottlenecks for the industrialization of second-generation biobutanol production. An effective strategy to decrease the wastewater discharge in biobutanol fermentation process is broth recycling (BR). Nevertheless, the conventional BR process suffered from server organic-acid by-products inhibition, causing low butanol yield. In this study, to solve the barrier, active carbon (AC) adsorption system was hybrid with the acetone-butanol-ethanol (ABE) fermentation and ex-situ product separation (ESPR) units. After fermentation and pervaporation, organic acids that remaining in the ABE-separated broth were partially adsorbed onto AC so that improve the continuity and efficiency of the BR process. The physicochemical characterizations of different types of commercial ACs and the organic acids adsorption efficiency was evaluated by analyzing the static and dynamic adsorptions kinetics. When adopting the DD-type AC (code C299105), the better adsorbent for organic acids removal, 87.50% of fermentative wastewater can be saved whilst the ABE concentrations were also kept constantly at 15.22 +/- 0.45 g L-1 in the following cycles of fermentation, and the ABE productivity was almost no changed (0.21 +/- 0.01 g L-1 h(-1)) after 3 cycles of operation. Therefore, the AC assisted ESPR process is an attractive method for ABE production with low wastewater discharge.