Application of Sewage Sludge and Other Amendments to Coal Refuse Material: I. Effects on Chemical Composition

Abstract

AbstractThe effects of sewage sludge, lime, and gypsum on the chemical composition of coal refuse material were examined at a Fulton County, IL, land reclamation site. Treatments consisted of a control, 542 dry Mg ha−1 anaerobically digested sewage sludge, 89.6 Mg ha−1 lime, 112 Mg ha−1 gypsum, and combinations of these amendments. Analysis of coal refuse material (0–15 cm) from 1976 to 1981 showed that the sewage sludge + lime treatment was the most effective in maintaining the refuse pH, and in reducing water‐soluble Al and Fe, KCl extractable Al, and total acidity. Gypsum applications decreased the refuse pH and increased water‐soluble Al and Fe, KCl extractable Al, and total acidity. The effectiveness of treatments in reducing total acidity was sewage sludge + lime > gypsum + sewage sludge + lime > sewage sludge > lime > gypsum + sewage sludge > control > gypsum + lime > gypsum. Concentrations of water‐soluble Ca, Mg, and Na reflected the additions of these cations made by various treatments and the contribution of these cations to refuse electrical conductivity (EC). Profile sampling (0–100 cm) in 1976 and 1981 showed a decline in pH, and an increase in water‐soluble Al and Fe and total acidity in 1981 samples from the sewage sludge and gypsum treatments. The changes in the sludge treatment indicate there was a solubilization of metals from the refuse material and sewage sludge with time, as the surface pH (0–15 cm) declined, and a subsequent increase in the total acidity from metals and acidic by‐products leached to the 15‐ to 100‐cm depths of the coal refuse material. In the gypsum treatment, the changes observed in the 1981 profile samples reflected the leaching of H3O+, metals, and acidic by‐products of pyrite oxidation produced by exchange with Ca from the gypsum amendment.