Characterization of Phosphorus in Sludge Extracts Using Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy
- Zeina R. Hinedi *,
- A. C. Chang and
- R. W. K. Lee
Nuclear magnetic resonance spectroscopy (31P NMR) was used to characterize the phosphorus (P) extracted from selected municipal sewage sludges. Aqueous and nonaqueous extraction schemes were studied. The trichloroacetic acid/KOH two-step extraction and the 0.5 M NaOH extraction were effective in recovering P from sludges. It was found that the P distribution pattern is sludges was affected by the sludge digestion processes. Almost all of the P in anaerobically digested sludges was inorganic. In the waste-activated sludge and aerobically digested sludges, more than 50% of the total P was present as P-monoesters and P-diesters. Several experiments were conducted to confirm P-diester peak assignment. Incubation of the sludge with ribonuclease caused a decrease of the peak in the P-diester region, indicating that at least a part of the P-diesters is in the form of RNA. Results of a dialysis experiment appeared to indicate that P-diesters were broken down from the molecular weight >1000 material to their lower molecular weight components during sludge digestion. The peaks appearing in the 31P NMR spectra of sludge-borne phospholipids were tentatively assigned to phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and phosphatidylglycerol or diphosphatidylglycerol.
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