Call 03

We invest in
Proofs of Concept
and Round Seeds

From May 30 to July 31, 2021

08. Recovery of digestates from treatment plants.


After applying a solid-liquid separation to the digestates, a solid phase of stabilized sludge and a liquid phase (also called centered) are obtained with a high content of nutrients -nitrogen, phosphorus and potassium- which are the basis of a large number of fertilizers. It is directly applied as a fertilizer in crop fields or the liquid phase is reintroduced – once separated from the solid – at the head of the water line of the WWTP itself. Both options carry environmental problems. If direct application to crops is chosen, the high nutrient content can lead to groundwater contamination and eutrophication. On the contrary, reintroduction at the headwaters decreases the C / N ratio in the incoming wastewater, which hinders the biological denitrification process and makes it necessary to add chemical compounds as a source of organic matter. TTAF seeks solutions based on new technologies to recover and revalue these compounds, allowing a better application of the concepts of the circular economy to the liquid and gaseous effluents of the anaerobic digestion of sludge: carbon chains, phosphorus, nitrogen and the set of nutrient concentrates. in aqueous solution.

Possible approaches

More efficient natural fertilizers Nitrogen recovery by economically sustainable energy procedures. Recovery of phosphorus by selective precipitation

Solutions not of interest

Technologies in TRL <3 Unsustainable or economically unfeasible procedures.