OPTIMIZATION OF PHOSPHORUS REMOVAL IN EBPR WASTEWATER SYSTEM BY EXTERNAL CARBON SOURCE ADDITON

Abstract

The overall goal of this study is to investigate the effect of carbon source (sodium acetate) addition as an application of Enhanced Biological Phosphorous Removal (EBPR) in the modified contact stabilization activated sludge system, by using contact tank as a phosphorus uptake zone and using thickener tank as a phosphorus release zone. The study involved the construction of a pilot plant which was setup in the Quhafa Wastewater Treatment Plant (WWTP), Al-Fayoum, Egypt. Results showed the removal efficiencies of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5) and Total Phosphorus (TP) of this pilot plant were 86%, 85% and 59%, respectively. On the other hand, results showed that sodium acetate addition has decreased the biodegradability of the organic matter by phosphorus accumulating organisms (PAOs) which is represented in the ratio between COD/BOD5 in the release zone in the thickener as it reached five times. Moreover, addition of sodium acetate caused a turbulence in phosphorus release efficiency in the anaerobic zone where it reached -96%. Finally addition of sodium acetate to the anaerobic zone did not improve the performance of the overall system in general and the release efficiency in particular. In addition, a simple mathematical model for phosphorus release was developed based on a batch test and release rates were measured.