Phosphorus recovery by use of sludge fractionation
In working towards a sustainable society, recycling and recovery of products together with handling of scarce resources must be considered. The growing quantities of sludge from wastewater treatment plants and the increasingly stringent restrictions on landfilling and on agricultural use of sludge are promoting other disposal alternatives. Sludge fractionation, providing sludge volume reduction, product recovery and separation of toxic substances into a small stream, has gained particular interest. The potential for phosphate release and recovery from treated sewage sludge was investigated in Kristina Stark’s PhD-thesis as an alternative for agricultural use in urban areas. Leaching and recovery experiments were performed on different sludge residues.
Results showed that acid or alkaline leaching is a promising method to release phosphate from sewage sludge treated with supercritical water oxidation, incineration, or drying at 300°C. The leaching is affected by a number of factors, including how the sludge residue has been produced, the origin of the sludge residue, the quantity
of chemicals added and the presence of ions in the leachate.
The results may be beneficial for minimizing the use and cost of chemicals, and give increased knowledge for further development of technology for phosphate recovery.