Degradation and toxic effects of acrylic acid on anaerobic systems

The objective of this study was to determine the anaerobic degradability of acrylic acid in both acidogenic and methanogenic systems. Enriched acetate, propionate, and glucose cultures were used in batch serum bottles and chemostats. The results showed that the acrylic acid was degraded to propionate and acetate, and without acclimation it completely inhibited propionate degradation and partially inhibited acetate degradation. The maximum specific rate constant k and the half-saturation constant Ks, for the acrylic acid degradation were 0.22 d(-1) and 7.2 mg/L, 0.40 d(-1) and 16.8 mg/L, and 1.2 d(-1) and 22.9 mg/L for the acetate, propionate, and glucose cultures, respectively. The inhibition coefficient K-l for acetate degradation in the presence of acrylic acid was 4.2 mg/L. In both the methanogenic and acidogenic chemostats, 98% of the acrylic acid was removed. However, the acidogenic chemostat had a significantly higher loading rate (416 mg/L . d) than the methanogenic chemostat (16.7-66.7 mg/L . d). Even at low acrylic acid loading, the propionate utilizers required a long time to acclimate to acrylic acid. Without such acclimation, acrylic acid fed anaerobic systems can lead to process failures.