2024 年 22 巻 1 号 p. 53-60
The oxygen radical absorbance capacity (ORAC) was used to evaluate the antioxidant activity of conventional activated sludge. Protein and ORAC assays showed that extracellular polymeric substances (EPS) accounted for ~80% of the total protein extracted from conventional activated sludge and ~50% of the total ORAC. The detection of ORAC and superoxide dismutase activity suggests that EPS potentially possess antioxidant capacity. The intracellular antioxidant activity of conventional activated sludge in a municipal wastewater treatment plant was investigated. The activated sludge showed larger variations in ORAC in tanks without aeration than with aeration, which may be attributed to variability in oxygen diffused from the atmosphere and organic matter available for each bacterium. In addition, the variation in ORAC of tanks with aeration gradually decreased over time, which may be attributed to the generation of reactive oxygen species and the production of antioxidants balancing out the decrease in organic matter concentration. However, in a laboratory-scale experiment, ORAC decreased at 1.5 h under the oxic condition, which may be attributed to less available energy for producing ORAC in the internal storage material.
