Chemical fractionation of phosphorus in stabilized biosolids

Xiao Lan Huang, Yona Chen, Moshe Shenker*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Three chemicals - ferrous sulfate (FeSul), calcium oxide (CaO), and aluminum sulfate (alum) - were applied at different rates to stabilize P in fresh, anaerobically digested biosolids (FBS) obtained from an activated sewage treatment plant. A modified Hedley fractionation procedure was used to assess P forms in these sludge-borne materials and in a biosolids compost (BSC) prepared from the same FBS. Each biosolids material exhibited a unique pattern of P distribution among fractions. The most available P forms, namely: (i) water-soluble P (WSP); (ii) membrane-P; and (iii) NaHCO3-P, were stabilized by small rates of each of the chemicals; but the P transformation into more stable forms depended on the type of chemical added. The stabilized P forms were enhanced by high rates of CaO and FeSul, but were reduced by high rates of alum. The organic P (Po) in the first three fractions of the FeSul- and alum-stabilized biosolids was enhanced by the chemical addition, and Po transformation from NaOH-Po into NaHCO 3-Po was found in calcium-stabilized biosolids. A positive relationship was found between NaHCO3-Po and the NaHCO3-extracted organic C in all chemically stabilized biosolids. One-step extraction by NaHCO3 or NaOH underestimated P extraction compared to the stepwise extraction. The reported results are consistent with solid-state P speciation reported earlier and contribute important information for optimizing biosolids stabilization to reduce P loss after incorporation in soils and for maximizing soil capacity to safely store pre-stabilized biosolids.

Original languageAmerican English
Pages (from-to)1949-1958
Number of pages10
JournalJournal of Environmental Quality
Issue number5
StatePublished - Sep 2008


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