Abstract: Enzyme plays an important role in enhanced biological phosphorus removal(EBPR); however, little attention was paid on this issue in the literature. Based on the investigations of the activities of some key enzymes related to EBPR, the relationships between enzyme activity and phosphorus-accumulating organisms(PAO) sludge yield coefficient, and between enzyme activity and soluble ortho-phosphorus were studied. In the range of pH 6.4—7.6, the results showed that the activity of dehydrogenase, adenylate kinase and polyphosphate kinase increased linearly with pH, while acid- and alkaline-phosphatase activity were not influenced by pH. It is found that a linear relationship was shown between PAO sludge yield coefficient and dehydrogenase activity, anaerobic phosphorus release rate and adenylate kinase activity, and aerobic phosphorus uptake rate and polyphosphate kinase activity, respectively. The results indicate that a higher pH was beneficial to the growth and the activity of PAO, which led to an improved phosphorus removal performance.

Key words: Enzyme activity, pH value, Enhanced biological phosphorus removal