Relation between sludge carbohydrate content and biological phosphate removal

The relationship between sludge carbohydrate (CH) content and phosphate (P) removal performance has been studied in three sequencing batch reactors exhibiting enhanced biological phosphorus removal (EBPR). The P removal performance was good when the sludge CH content was low (9–10% CH/MLSS), but it declined concomitantly as the sludge CH content increased. The sludge CH content was found to be a reliable parameter representing its capacity for P removal. The anaerobic degradation and aerobic synthesis of sludge CH was a dominant metabolic activity of the sludge. It was responsible for the change of sludge CH content. Factors influencing this activity were analyzed. The study, as a whole, suggests that the control of sludge CH content to low levels would be a prerequisite for achieving enhanced P removal in the EBPR process.