Observations relating to enhanced phosphorus removal in biological systems

Abstract In this work chemical fractionation and 31 P-NMR spectroscopy were employed to explore certain unique characteristics of activated sludge exhibiting enhanced phosphorus removal. Two sequencing batch reactors were used in this research. The two reactors have been maintained in an environmental chamber and operated under the same conditions for well over 3 years. The only difference between the reactor systems is one system receives a portion of its organic carbon in the dissolved form as glucose (D-reactor) while the second reactor (P-reactor) receives an equivalent amount of organic material in the particulate form as starch. Chemical fractionation data and 31 P-NMR analysis indicate that in the D-reactor, during periods of enhanced P-removal, transient phosphate is stored primarily as high molecular weight polyphosphates and nucleic acids. A portion of the transient polyphosphate is located outside the cytoplasmic membrane and is cell bound. No polyphosphate was found to exist in the mobile form in the cytoplasm. On the other hand, similar analysis on sludge taken from the P-reactor, during periods of enhanced P-removal, indicate that transient phosphate is stored primarily as low molecular weight polyphosphate. The transient polyphosphate is located inside the cytoplasmic membrane. A portion of the polyphosphate is cell bound while the remainder exists in the mobile form in the cytoplasm. Kinetic analysis suggests the possibility of a chemical intermediate(s) being formed in the degradation of polyphosphate to orthophosphate in sludge from the D-reactor while in sludge from the P-reactor the degradation process appears to proceed directly from polyphosphate to orthophosphate.