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TECHNICAL REPORTS

Waste Management

Lability of Drinking Water Treatment Residuals (WTR) Immobilized Phosphorus

Aging and pH Effects

Soil and Water Sci. Dep., Univ. of Florida, Gainesville, Fl 32611-0510

^* Corresponding author (agyin{at}ufl.edu)

Received for publication December 14, 2006. Time constraints associated with conducting long-term (>20 yr) field experiments to test the stability of drinking water treatment residuals (WTR) sorbed phosphorus (P) inhibit improved understanding of the fate of sorbed P in soils when important soil properties (e.g., pH) change. We used artificially aged samples to evaluate aging and pH effects on lability of WTR-immobilized P. Artificial aging was achieved through incubation at elevated temperatures (46 or 70°C) for 4.5 yr, and through repeated wetting and drying for 2 yr. Using a modified isotopic (³²P) dilution technique, coupled with a stepwise acidification procedure, we monitored changes in labile P concentrations over time. This technique enabled evaluation of the effect of pH on the lability of WTR-immobilized P. Within the pH range of 4 to 7, WTR amendment, coupled with artificial aging, ultimately reduced labile P concentrations by 75% relative to the control (no-WTR) samples. Soil samples with different physicochemical properties from two 7.5-yr-old, one-time WTR-amended field sites were utilized to validate the trends observed with the artificially aged samples. Despite the differences in physicochemical properties among the three (two field-aged and one artificially aged) soil samples, similar trends of aging and pH effects on lability of WTR-immobilized P were observed. Labile P concentrations of the WTR-amended field-aged samples of the two sites decreased 6 mo after WTR amendment and the reduction persisted for 7.5 yr, ultimately resulting in 70% reduction, compared to the control plots. We conclude that WTR application is capable of reducing labile P concentration in P-impacted soils, doing so for a long time, and that within the commonly encountered range of pH values for agricultural soils WTR-immobilized P should be stable.

Abbreviations: Al-WTRs, alum-based WTR • DPS, degree of P saturation • Fe-WTRs, iron-based WTR • ICP–AES, inductively coupled plasma–atomic emissions spectroscopy • PSI, P saturation index • SAS, statistical analysis system • SSA, specific surface area • TSP, triple superphosphate • WSP, water-soluble P • WTR, drinking water treatment residuals

This article has been cited by other articles:

				S. Agyin-Birikorang, G. A. O'Connor, and S. R. Brinton Evaluating Phosphorus Loss from a Florida Spodosol as Affected by Phosphorus-Source Application Methods J. Environ. Qual., May 1, 2008; 37(3): 1180 - 1189. [Abstract] [Full Text] [PDF]