Proceedings

Sewage sludge typically contains between about 3 – 6 % of phosphorus in the dry mass and can act as a secondary source for phosphorus. In the year 2019 a European Union directive can be expected regarding the recovery of phosphorus from municipal sewage sludge with Germany having already implemented such laws on the national level.

The most advanced technology with regards to phosphorus recovery from sewage sludge is the EuPhoRe® Process avoiding most of the technological disadvantages of existing competing technologies, which are typically a combination of incineration and a subsequent more or less costly and complicated thermo-chemical treatment of incineration ashes.

The EuPhoRe® Process combines a thermal treatment of dewatered (pre-dried) sludge at ca. 650 – 750°C (featuring gasification of the volatile matter into a process gas with co-current volatilization of heavy metals by additives) and a subsequent incineration at 900-1,100°C of the coke deriving from the thermal treatment stage.

The process gas shall be incinerated, whereas flue gases will undergo adequate flue gas cleaning in order to primarily catch the heavy metals.

The product is an ash of about 14 – 24 % phosphorus content as phosphates being readily available for plants and which are to be combined with other fertilizer ingredients.

Preferably, the process shall be retrofitted either to coal or to waste-to-energy plants with existing high rate flue gas cleaning in place. However, stand-alone solutions are technically and economically feasible.
The process has been operated at full scale in 2 plants in Switzerland, and an additional 5 plants will start their construction in Germany in late 2018 (the biggest for 135,000 t/a of dewatered sewage sludge as a retrofit plant to an existing waste-to-energy plant).

Keywords
Heavy Metal Removal from Ashes, Phosphates Plant Availability, Phosphorus Recovery, Sewage Sludge