The Role of Bacterial Phosphate Metabolism in Enhanced Phosphorus Removal from the Activated Sludge Process

Abstract

This study was undertaken in an attempt to gain greater insight into phosphate metabolism in relation to biological phosphorus removal. Bacterial population studies of activated sludge plants revealed the predominance of Acinetobacter spp. Studies of these isolates showed a number of strains capable of reducing nitrate to nitrogen. Growth of Acinetobacter isolates on a variety of carbon sources showed that not only growth but also polyphosphate accumulation is stimulated by short chain carbon compounds, such as acetate and butyrate, which are products of bacterial fermentation. Assays of anaerobic zone mixed liquor samples indicated high activity of key enzymes in the formation of these compounds. Phosphate uptake under various conditions underlined the sensitivity of bacterial phosphorus metabolism to external factors. The origin of the orthophosphate released in the anaerobic zone points strongly to polyphosphate hydrolysis to orthophosphate rather than the formation of adenosine triphosphate (ATP). The anaerobic zone is seen as a qualifying zone where cells are preconditioned for optimum phosphorus removal in subsequent zones.