Potential benefits and risks of land application of sewage sludge

Sewage sludge, also referred as biosolids, is a byproduct of sewage treatment processes. Land application of sewage sludge is one of the important disposal alternatives. Characteristics of sewage sludge depend upon the quality of sewage and type of treatment processes followed. Being rich in organic and inorganic plant nutrients, sewage sludge may substitute for fertilizer, but availability of potential toxic metals often restricts its uses. Sludge amendment to the soil modifies its physico-chemical and biological properties. Crop yield in adequately sludge-amended soil is generally more than that of well-fertilized controls. Bioavailability of metals increases in sludge amended soil at excessive rates of application for many years. Plants differ in their abilities to absorb sludge-derived metals from the soil. The purpose of this paper is to review the available information on various aspects of sewage sludge application on soil fertility and consequent effects on plant production to explore the possibility of exploiting this byproduct for agronomy and horticulture.