INNOVATIVE TECHNOLOGIES FOR PHOSPHORUS RECOVERY FROM SEWAGE SLUDGE ASH

The scarcity in Europe of phosphate ore along with the constantly growing demand for phosphorus-based products make it essential to find new sources and innovative recovery techniques for phosphorus in all of its forms. In order to avoid phosphate rock reserves exhaustion, its recovery from incineration Sewage Sludge Ash (SSA) might be a solution. Phosphorus concentration in municipal SSA is 9% (Kruger et al., 2014), which is within the range of the currently mined phosphate rock. However, the high amount of metallic elements (especially iron and aluminium) leads to a higher consumption of concentrated sulphuric acid, as it is used for the phosphate mineral treatment. The aim of this preliminary survey is to assess the acid demand and the efficiency of different acids towards the dissolution of the phosphate minerals in ash, Elemental and mineral composition, leachability and further tests were performed using four different SSA samples originated from three different sewage sludge incinerators located in Germany. First results show that the extraction yields with organic acids are higher compared to the ones achieved with mineral acids, Especially for oxalic acid, for which dissolution occurs both due to protonation and reduction, extraction rates close to 100% were achieved using lower amounts of acid.