Comparative Study of Enterobacter aerogenes and Mixed-Culture Bacteria for Acrylamide Biodegradation in Sequencing Batch Reactor Wastewater-Treatment Systems

Abstract

Most recent researches have focused on acrylamide (AM) biodegradation with the pure culture of various microorganisms including Enterobacter aerogenes. In this study, the acrylamide biodegradations from synthetic wastewater containing different acrylamide concentrations by mixed-culture bacteria, E. aerogenes, and a mixture of both bacteria in a sequencing batch reactor (SBR) wastewater-treatment systems controlled at the solid retention time (SRT) of 1 days were comparatively evaluated under aerobic conditions. The results revealed that both bacteria could immediately remove acrylamide in the SBR systems, but E. aerogenes did not biodegrade acrylamide as efficiently as reported in culture media. The growth rate of E. aerogenes was limited at 1 days SRT, resulting in low biomass production and intracellular polyphosphate accumulation, thereby reducing heterotrophic nitrification. However, it was found that E. aerogenes removed acrylamide at higher rate than mixed-culture bacteria in the SBR system. In this study, it is reported that free ammonia nitrogen (FAN), as one product from acrylamide biodegradation, inhibited amidase activities, resulting in lower acrylamide removal efficiencies in the SBR systems after a long-term operation. FAN also inhibited autotrophic nitrification in the SBR system containing mixed-culture bacteria, resulting in FAN accumulation. A mixture of both bacteria enhanced acrylamide biodegradation because simultaneous autotrophic nitrification and heterotrophic nitrification minimized the FAN accumulation.