| Parameters bearing on the performance of a full-scale 88-MGD enhanced biological phosphorus removal (EBPR) system were examined. Samples were collected for a 10-month period in a basin and in a secondary clarifier of the plant. Samples were analyzed for nitrate, total and ortho-phosphorus, COD, acetic acid, polyhydroxybutyrate, glycogen, calcium, magnesium, potassium, ammonia, alkalinity, TSS, ORP, pH, and DO. Profiles of the aerobic and anaerobic zones, and secondary clarifier showed that the plant is operating as an actual EBPR system, with sporadic phosphorus excursions. Low BOD input to the system, high phosphorus from return streams of the sludge handling process, high nitrates in the RAS, and strong denitrification in the secondary clarifiers were identified as potential causes for the occasional excursions. A correlation was found between TSS and nitrate concentrations in the RAS, indicating that the former may serve as a good parameter for controlling denitrification in secondary clarifiers. |
