In the context of ecological transition and circular economy, sludge from urban and industrial wastewater treatment is no longer a mere disposal burden—it has become a carrier of high-value resources. Phosphorus and heavy metals, present in significant concentrations, can be extracted and reintegrated into production cycles, contributing to environmental sustainability and raw material security.
Phosphorus is a non-renewable resource essential for agriculture and the food industry. Global reserves are geographically concentrated and subject to geopolitical tensions. In sludge, phosphorus is bound to organic and inorganic compounds (mainly Ca, Fe, and Al salts), requiring advanced technologies for its recovery.
ETIS® (Ecological Transition Innovative Solution) stands out as a key technology. Its alkaline hydrolysis process not only breaks chemical bonds—it radically transforms the sludge matrix, making phosphorus more available and selectively recoverable.
Once released, phosphorus can be recovered through:
Integrating ETIS into treatment processes marks a qualitative leap toward circularity, making phosphorus recovery not only feasible but economically and technically advantageous.
Sludge contains high-density metals such as copper, zinc, nickel, lead, and chromium, subject to strict environmental regulations. Their management requires differentiated approaches:
1. Inertization/Stabilization – reduces mobility and bioavailability, making sludge suitable for disposal
2. Selective Recovery
These methods allow contaminants to be transformed into secondary raw materials for the metallurgical industry.
An advanced technological model involves the sequential combination of processes: phase, objective, technologies
Phase1. Solid-liquid / Objective: separation concentration of metals and organics in sludge / Technologies: mechanical dewatering, polyelectrolytes
Phase 2. Phosphorus recovery / Objective: extraction of orthophosphates and struvite precipitation / Technologies: liquid fraction treatment
Phase 3. Metal valorization / Objective: selective extraction from dewatered sludge / Techonologies: leaching, chemical separation
This scheme enables the production of contaminant-free digestates, renewable fertilizers, and reusable metals—dramatically reducing waste volumes.
Recovering phosphorus and heavy metals from sewage sludge is no longer a distant possibility—it’s a technologically mature and strategically necessary reality. Thanks to integrated solutions like ETIS® – Ecological Transition Innovative Solution, it is now possible to transform a critical waste into a multifunctional resource, reducing environmental impact and generating value for agriculture, industry, and local communities.
The approach proposed by SDG s.r.l. shows how innovation can drive ecological transition, with technologies that not only solve problems but create opportunities. Sludge becomes a green factory, capable of returning nutrients and raw materials to the system, fully aligned with the principles of the circular economy.
The challenge is no longer just technical—it’s cultural, industrial, and environmental. And SDG s.r.l. is ready to meet it.
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