Reusing Phosphorus : Engineering Possibilities and Economic Realities

Recycling is becoming increasingly important in rich societies both in a physical sense and in the perceptions about desirable changes of economic activity and behavior. In both respects, the significance of recycling is greatest for the raw materials of agricultural, forest, and mineral origins. Recycling of phosphorus, secondary phosphorus originating from wastewater is discussed in this paper. The recycling of phosphorus from wastewater currently involves the reuse of sewage sludge in agriculture. In Sweden, 84 percent of the population is connected to wastewater treatment plants where phosphorus is removed from the wastewater, hence producing sludge containing high levels of phosphorus. The phosphorus content is 6,000 metric tons per year in Swedish wastewater treatment plant sludge. This represents approximately 30 percent of the commercial phosphorus fertilizer used yearly in Sweden. The use of sewage sludge in agriculture has been discussed widely in Sweden during the 1990s. Far from resolving several important issues, such as the content of pollutants in the sludge and whether the content of phosphorus in sludge can be used by plants, the debate is still raging.Godkänd; 1999; 20070203 (ysko)