Ashes from Sewage Sludge and Bottom Sediments as a Source of Bioavailable Phosphorus

Abstract

Phosphorus is an element necessary for the growth of plants, and as phosphate rock gets depleted, it becomes an increasingly scarce resource. Therefore, it seems necessary to implement simple methods of cheap and effective phosphorus recovery from waste. Particularly valuable sources of phosphorus are ashes of municipal sewage sludge and bottom sediments. However, these materials usually carry significant amounts of pollutions, including heavy metals. Optimization of ash phosphorus sequential extraction methods from a thermal conversion of sewage sludge and bottom sediments allows to select an effective and uncomplicated technology of phosphorus recovery, while maintaining low heavy metal pollution, which is one of the main restrictions in use of ashes. Determination of an amount of bioavailable phosphorus is therefore a basis for estimation of the possibility of using it from waste. Extraction using the Golterman method or shaking out with calcium lactate or Trougs reagent indicate that ashes from sewage sludge and bottom sediments are rich sources of bioavailable phosphorus, which usage in field conditions is a viable alternative to fertilizers containing fossil phosphorus.

Keywords

• sewage sludge
• phosphorus
• bioavailability
• extraction
• bottom sediments
• ash