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Appl Environ Microbiol. 1970 July; 20(1): 145-150
Copyright © 1970 American Society for Microbiology. All Rights Reserved.

Biological Uptake of Phosphorus by Activated Sludge ¹

Department of Microbiology and Medical Technology, The University of Arizona, Tucson, Arizona 85721

ABSTRACT

The ability of activated sludge to remove phosphates was studied by adding carrier-free ³²P to raw sewage and measuring incorporation of the radioactivity into the cells over a period of time. Radioisotope determinations indicated that 48% of the ³²P radioactivity was removed by 12 hr. However, chemical methods indicated that only 30% of the orthophosphate apparently disappeared from the sewage during this period. Experiments with sludge prelabeled with ³²P indicated that considerable phosphate turnover occurred. The cells released large amounts of radioactivity as they were incorporating fresh phosphates. Starvation in isotonic saline for 18 hr caused the sludge to dump phosphate. When introduced into fresh sewage containing ³²P, the starved sludge removed about 60% of the radioactivity in 6 hr with little phosphate turnover. The ability of sludge to remove ³²P was inhibited approximately 83% by 10^–3M 2,4-dinitrophenol. This inhibition was at the expense of the cell fraction that contained ribonucleic acid and deoxyribonucleic acid. The sludge cells released orthophosphate when exposed to the chemical agent. Experiments using ⁴⁵Ca indicated that calcium phosphate precipitation plays a minor role in phosphate removal under our experimental conditions.

¹ Report of this investigation was presented at the 70th Annual Meeting of the American Society for Microbiology at Boston, Mass., 26 April-1 May 1970.