Glass Fertilizers Obtained Using Sewage Sludge ASH Wastes

The sewage sludge ash represents an important waste both in terms of the generated quantities and the phosphorus content. Starting from these premises, the present paper proposes an alternative way to use these ash as vitreous fertilizers. Another waste with potential applicability for this purpose is the sludge from the deep water treatment plants, which has a high iron content, an essential microelement for plants development. The paper addresses two aspects: the kinetic study of the solubilisation process of potassium, phosphorus and iron ions from the obtained fertilizers and their effect on barley plants respectively. The kinetic study using the model of infra particular diffusion revealed the process of ionic solubilisation process in two distinct steps: one slow, speed controlling - diffusion through the glass matrix, and second, faster - diffusion through the medium particle boundary. The fertilizing effect, analysed using specific parameters: germination percent, biomass and plant length, recommends as optimal the composition with the maximum addition of ash.