Anaerobic biotransformation of acrylic acid in uasb reactors: Significance of process staging, physical homogenization of microorganisms and microbial acclimation

Anaerobic biotransformation of acrylic acid was investigated in UASB reactors with three different cultures, namely granular, homogenized (crushed) granular and acrylate-acclimated acetate-enriched Methanosarcina. The microbial acclimation, operational parameters such as F/M ratio, influent concentration and loading rate of acrylic acid as well as process staging and significance of physical homogenization (crushing) of microorganisms were emphasized in the experiments. Results indicated that a single-stage UASB with granular biomass biotransformed acrylic acid (influent concentration of 3000 mg l⁻¹) to acetic and propionic acids efficiently, but these intermediate products could not be metabolized efficiently (<45% COD removal). A two-stage UASB with the same culture, on the other hand, metabolized acetic and propionic acids efficiently and provided more than 97% COD removal for the same influent acrylic acid concentration. Furthermore, the significance of homogenizing granules and acclimating the cultures on process performance were clearly observed.