Land application of sewage sludge: Phosphorus considerations

Abstract

Phosphorus considerations are gaining increasing attention where sewage sludges are applied to land because of the continuing trend of rising P levels in sludges and the growing concern for environmental pollution and nutrient recycling issues. P in sludges has reached levels comparable to inorganic fertilizers in some cases while currently average values will be in the region of 2% P (dry solids basis). In reactions with soils the soluble component (or that capable of being solubilized) will be the most important fraction. Potential benefits to be gained from sludge applied P are large while hazards from disposal of sludge P are minimal owing to the transformations which P undergoes in soils. The finite world supply of resource P and the escalating costs of inorganic P fertilizers warrants that further research be directed towards making sludges more acceptable as a source of this nutrient. Unacceptable P pollution of the environment is an added stimulus to effectively dispose of and utilize such wastes simultaneously.