Phosphorus release-storage reaction and organic substrate behavior in biological phosphorus removal

Abstract

This paper represents the results of an experimental investigation conducted on the mechanism of biological phosphorus removal. The relationship between phosphorus release-storage reaction, and behavior of extracellular and intracellular organic substrates under anaerobic-aerobic conditions is studied in detail. The results obtained are as follows: (1) the amount of intracellular carbohydrate increases under the presence of extracellular glucose, but decreases when extracellular glucose is depleted in the anaerobic condition. (2) The amount of intracellular poly-β-hydroxybutylate (PHB) gradually increases under the anaerobic condition. The increase in intracellular PHB content appears to be related to the decrease in intracellular carbohydrate content when extracellular glucose is depleted. (3) Rate of phosphorus release under the anaerobic condition is related to the amount of releasable phosphorus in the cells. The observed ratios of postulated “maximum phosphorus storage capacity” to total amount of intracellular phosphorus are similar to those of the low molecular weight polyphosphate fraction in the cells. (4) Release of phosphorus under the anaerobic condition appears to be related to both ingestion of extracellular organic substrates and formation of intracellular PHB. (5) Release of phosphorus under the anaerobic condition appears to be limited once a fixed portion of intracellular phosphorus is released, even if substantial amount of extracellular organic substrate still remains available. (6) The amount of intracellular PHB increases in the subsequent aerobic condition under presence of a sufficient amount of extracellular organic substrate, but the amount decreases when the extracellular organic substrate is depleted. Similarly, the amount of intracellular carbohydrate initially increases, then gradually decreases following the decrease in PHB content. (7) Ingestion rate for phosphorus in the aerobic condition appears to be dependent on unsaturated storage capacity of intracellular phosphorus as well as on the concentration of extracellular phosphorus.