Effects of different rates of fly ash and sewage sludge mixture amendments on cation availability and their leachability

Abstract

A leaching column study was conducted to evaluate the leaching of cations from soils amended with a mixture of (1:1) fly ash (FA) from Port Wentworth power plant, Savannah, GA: sewage sludge (SS) from President Street water pollution control plant, Savannah, GA. Two sets of soil-leaching columns (30-cm high and 7.5-cm diameter; 15 columns per soil) were prepared with a fine sandy soil from Florida (Candler fine sand; pH 6.8) and Georgia (Ogeechee loamy sand; pH 5.6). The top one inch of soil from each of these columns was amended (3 columns per treatment) with 1:1 mixture of SS and FA at either 0, 24.7, 49.4, 98.8 or 148.3 Mg ha^{− 1} rate. After saturating the columns with deionized water, 18 cycles of intermittent leaching and drying was performed on weekly basis. Leaching of major cations and changes in ionic strength and pH were evaluated on half pore volume (220 mL) of leachate collected at each event. Results of this study indicated that leaching of cations increased rapidly up to the 3rd leaching event, and then rapidly decreased and the concentration of cations reached somewhat similar to that of unamended soil columns. Effects of soil type and rates of amendments on leaching of major cations along with changes of pH and ionic strength are discussed in this paper.

Keywords:

• Cations
• Coal combustion byproducts (CCBP)
• Leaching
• Soil amendment

Acknowledgment

This research was conducted with the funding made available through Department of Energy Grant # DE-FG09-96SR18558.

Notes

^a Total Elemental compositions were determined on acid digest by ICP-OES.

^b Collected from Port Wentworth Power Plant of Savannah Electric Company.

^c Collected from President Street water quality control plant of the city of Savannah.

^d Collected near Lake Alfred in Polk county, Florida.

^e Collected near Savannah in Chatham County, Georgia.

^†LSD values were calculated for cumulative amounts leached.