Potential use of combined elemental sulphur and sewage sludge as a fertilizer

Abstract

Sewage sludge and crushed elemental sulphur (S0) were combined in various ratios, and incubated under controlled conditions. Sulphur oxidation was strongly enhanced by addition of sewage sludge, though acidification of the mixtures prevented more than 4% of the initial sulphur to be converted to sulphate. Sub-samples of these incubated mixtures were then added to soil, and compared to soil amended with S0 and Na2S04. The sludge and S0 mixtures oxidized rapidly when introduced to the soil environment. Nearly 60% of the S0 from these mixtures oxidized within six weeks, compared to about 25% oxidation of S0 applied without sewage sludge. Indigenous S0 bacterial oxidizers in the sludge may explain the observed enhancement of S0 oxidation. Combinations of S0 and de-watered sewage sludge may provide an inexpensive and effective sulphur fertilizer source for western Canadian farmers in the future.