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Release of Phosphorus from Waste-Activated Sludge

Fine, P., Mingelgrin, U.
Soil Science Society of America journal 1996 v.60 no.2 pp. 505-511
sandy soils, calcareous soils, mixtures, phosphorus, organophosphorus compounds, solubility, kinetics, soil solution, nitrogen, nitrification, ammonification, calcium, soil pH, ionic strength, nitrate nitrogen, ammonium nitrogen, inorganic phosphorus, activated sludge
The dynamics of Prelease from a primarily domestic waste-activated sludge was investigated. More than 70% of the P in the sludge was in mineral form. The inorganic rather than the organic fraction controlled the release of P. Phosphorus release from soil-sludge mixtures into soil solution during 100 d of incubation was measured with and without a corn (L.) crop, in both a calcareous and a noncalcareous sandy soil. The kinetics of inorganic P dissolution from the sludge was also measured in aqueous suspensions during 9 d of incubation. Sludge concentrations were 10 to 100 g kg in the soil-sludge mixtures and 1 and 10 g L in the P-dissolution experiments. The dissolution experiments revealed that up to 40% of the total sludge P dissolved, under the experimental conditions. A continuum of solubilities was displayed by the solid inorganic P components present in the sludge, ranging from that of hydroxyapatite to that of dicalcium phosphate dihydrate. Transformations of N compounds in the sludge-containing systems had strong effects on the dynamics of P dissolution, mainly through the influence of the ammonification and nitrification processes on the pH and the ionic strength and composition of the aqueous solution.