The phosphorus fractions and alkaline phosphatase activities in sludge.

The alkaline phosphatase activities (APA) and phosphorus fractions in activated sludge during wastewater treatment were studied. Our results showed that the phosphorus concentration and fractions in activated sludge were highly correlated with the characteristics of influents. Inorganic phosphorus (IP) and non-apatite inorganic phosphorus (NAIP) were the main phosphorus fractions of sludge. A larger phosphorus concentration was found in activated sludge due to the more readily mobilizable and bio-available forms. The APA in sludge was directly correlated with mixed liquor suspended solids (MLSS) in activated sludge. The APA in the sludge is implicated the depletion of organic phosphorus forms in sludge, whilst also implying its less inhibition of inorganic phosphorus in sludge. The APA and phosphorus fractions in different sludge samples from the same wastewater treatment plant were quite stable. This stability shows their tight interactions in sludge.