Sewage sludge management in Spain
Sludge represents the second kind of urban waste
in Spain. 1.5 million
tons of dry matter is produced annually which means 7.5 million tons/year of humid matter to be
transported and managed.
Agriculture is the best use for sewage sludge thanks to Spanish characteristics with alkaline pH soils and deficiency of organic matter, as well as low contents of heavy metals in sludge. Using sludge for agriculture, there is no risk of acidification and the organic and nutrient sludge´s contents is the most environmentally sustainable and economically viable option. Low phosphorus contents in sewage sludge is also an important factor, especially in the current scenario of lack of phosphorus in the short term. The European Union has launched an initiative for phosphorus recovery form waste water, being the easiest and more economical option the use of sewage sludge in agriculture. An important progress in technical and scientific procedures is being carried out in the use of sewage sludge for agriculture, many of them being considered examples of good practices.
In relation to final disposal, 78.52% of Spanish sludge is used for land application (principally agriculture use), 3.22% for energetic valorization, 7.1% for incineration and, 11.16% is deposited in landfills.
In conclusion, sewage sludge of urban waste water can be valorized in agronomic uses, providing with important benefits for crops and soils. This use is the most important for sewage sludge, as it allows reconciling optimal management of sludge with fertilization of crops and improvement of soils, being a sustainable practice of resources saving.