Fly Ash and Lime Stabilization of Sewage Sludge- Changes to Phosphorous Solubility and Bioavailability

Yaniv Freiberg, University of Illinois at Urbana-Champaign
Shahar Baram, Institute of Soil, Water, and Environmental Sciences, Volcani Center
Michael Borisover, Institute of Soil, Water, and Environmental Sciences, Volcani Center
Pinchas Fine, Institute of Soil, Water, and Environmental Sciences, Volcani Center

Description

Fly Ash and Lime Stabilization of Sewage Sludge: Changes to Phosphorous Solubility and Bioavailability Authors Dr. Yaniv Freiberg - United States - University of Illinois at Urbana-Champaign Dr. Shahar Baram - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Dr. Michael Borisover - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Dr. Pinchas Fine - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Abstract Biosolids application to agricultural soils offers an alternative source of essential macro and micro plant nutrients that replace industrial products. In addition, the alkaline treatment of sludge offers virtually instantaneous pasteurization and stabilization. The objectives of our study were to investigate the chemical speciation and bioavailability of phosphorus (P) in an alkaline treated biosolids (NVS) in comparison with (i) the source sludge (SAeS; an excess-activated, secondary aerobic sludge) that was used for its production, and (ii) a sludge of an anaerobically digested sludge (ADSC). The NVS was produced by mixing the SAeS with coal-firing fly ash and burnt lime at a ratio of 60:35:5, respectively. The total P content (TP) of the SAeS, ADSC and NVS were 17.9, 22.8 and 3.7 g kg-1 dry weight, the solubilities of their P in water were 13.8, 9.2 and 2.5 g kg-1, and the cumulative TP extractability in water (repeated extended extraction at 1:60 ratio at pH 8) were 77, 40 and 67 (% of their TP), all respectively. The reduction in the P water extractability coincided with ortho-P (IP) precipitation with Ca2+ to form sparingly soluble Ca-P minerals and decreasing organic P content. The fresh, not yet carbonated NVS product maintained high overall P water extractability (67% of TP) and organic P content. These were inherited from its SAeS precursor sludge. Hence, although NVS has low TP content and low IP solubility, the overall potential IP extractability of the fresh product at soil pH is high. This seems to result from both mineral-P dissolution and organic P hydrolysis. This and other benefits (to soil structure, increased Mo and Se phytoavailability, soil disinfection) were also demonstrated in field experiments

 
May 14th, 3:30 PM May 14th, 5:00 PM

Fly Ash and Lime Stabilization of Sewage Sludge- Changes to Phosphorous Solubility and Bioavailability

Grand Rapids, Michigan

Fly Ash and Lime Stabilization of Sewage Sludge: Changes to Phosphorous Solubility and Bioavailability Authors Dr. Yaniv Freiberg - United States - University of Illinois at Urbana-Champaign Dr. Shahar Baram - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Dr. Michael Borisover - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Dr. Pinchas Fine - Israel - Institute of Soil, Water, and Environmental Sciences, Volcani Center Abstract Biosolids application to agricultural soils offers an alternative source of essential macro and micro plant nutrients that replace industrial products. In addition, the alkaline treatment of sludge offers virtually instantaneous pasteurization and stabilization. The objectives of our study were to investigate the chemical speciation and bioavailability of phosphorus (P) in an alkaline treated biosolids (NVS) in comparison with (i) the source sludge (SAeS; an excess-activated, secondary aerobic sludge) that was used for its production, and (ii) a sludge of an anaerobically digested sludge (ADSC). The NVS was produced by mixing the SAeS with coal-firing fly ash and burnt lime at a ratio of 60:35:5, respectively. The total P content (TP) of the SAeS, ADSC and NVS were 17.9, 22.8 and 3.7 g kg-1 dry weight, the solubilities of their P in water were 13.8, 9.2 and 2.5 g kg-1, and the cumulative TP extractability in water (repeated extended extraction at 1:60 ratio at pH 8) were 77, 40 and 67 (% of their TP), all respectively. The reduction in the P water extractability coincided with ortho-P (IP) precipitation with Ca2+ to form sparingly soluble Ca-P minerals and decreasing organic P content. The fresh, not yet carbonated NVS product maintained high overall P water extractability (67% of TP) and organic P content. These were inherited from its SAeS precursor sludge. Hence, although NVS has low TP content and low IP solubility, the overall potential IP extractability of the fresh product at soil pH is high. This seems to result from both mineral-P dissolution and organic P hydrolysis. This and other benefits (to soil structure, increased Mo and Se phytoavailability, soil disinfection) were also demonstrated in field experiments