EFFECTS OF CO-FIRING SEWAGE SLUDGE AND PLANT BIOMASS ONPHOSPHORUS AND POTASSIUM COMPOUNDS IN INCINERATED ASH

Abstract

 To investigate the changes in phosphorus and potassium during co-firing of sewage sludge with grass and woody biomass and to assess the potential of incinerated sewage sludge ash as a fertilizer, a laboratory incinerator was used to conduct co-firing tests of sewage sludge with cut grass and tree prunings. The incinerated ash resulting from the tests was subjected to various analyses (XRF, XRD and XAFS) and thermodynamic equilibrium calculations, and the compositional changes due to co-firing were summarized. Furthermore, the properties of incinerated ash as a fertilizer were evaluated through leaching tests. The addition of grass biomass during co-firing was found increase available potassium, which reacted with aluminum and silicate compounds in the sludge to form aluminosilicates. Additionally, phosphorus was transferred to calcium compounds and other compounds during the reaction process. Moreover, co-firing with both grass and woody biomass was found to enhance the citric acid–soluble forms of potassium and phosphorus available to plants, thereby increasing the value of incinerated ash as a fertilizer.