Sludge recycling and treatment

Creating virtuous circular economy loops

Just like water, sludge generated from wastewater treatment is a valuable resource that can be utilized. Being exemplary in terms of by-product valorization, innovation, and proactive collaboration, we work closely with local communities to develop reliable and sustainable solutions. From agronomic valorization to the production of green energy, Stereau prioritizes processes that reduce the volume of sludge produced and implement the most efficient and enduring energy valorization pathways, all within a circular economy framework, helping to transform environmental challenges into sustainable energy opportunities..

Stereau - Station d'épuration de Liffré (Ille-et-Vilaine) - production de biogaz à partir des eaux usées
Your challenges
  • You want to find a sustainable outlet for sludge and by-products from wastewater while reducing your greenhouse gas emissions.
  • You want to control the energy and carbon performance of your wastewater treatment plants to support your climate and energy strategy.
  • You want to secure the competitiveness and profitability of your facilities.
Our Solutions

Stereau offers tailored solutions for the treatment and valorization of sludge and by-products from wastewater treatment. Stereau ensures the following for each project:

  • Treatment performance in compliance
    with regulations
  • Optimizing sludge treatment
  • Facilitating the operation of your facilities
  • Optimizing investment and operating costs
  • Maximizing energy performance through the production of green energy
  • Achieving sustainable reduction in carbon emissions
Vue aérienne de la station d'épuration de Vence (Alpes-Maritimes)

Producing green energy through anaerobic digestion

Beyond their role in preserving aquatic environments, wastewater treatment plants are evolving towards a logic of renewable energy production and resource valorization.

By digesting sludge generated from wastewater treatment and converting it into biomethane through anaerobic digestion, communities can tap into a valuable source of green gas production, offering numerous advantages.

The anaerobic digestion of domestic wastewater treatment plant sludge enables the production of locally usable green gas. This mode of renewable energy production is gaining momentum as territories prioritize circular economy projects and aim to reduce dependence on fossil fuels. Stereau supports communities in projects of all sizes. Anaerobic digestion helps to reduce waste volume and convert it into renewable energy that replaces fossil fuel. Once captured, the biogas can be reused on-site and/or converted into biomethane for injection into the gas network.

The Furania wastewater treatment plant (Saint-Etienne Métropole) has benefited from Stereau’s expertise and innovative capabilities, with the construction of a biogas purification unit on-site for injection into the urban gas network.

This expertise was also recognized by the intermunicipal sanitation union of Marne-la-Vallée (SIAM), which awarded Stereau the concession contract in 2020 for wastewater treatment in its territory, including the construction and operation of an anaerobic digestion unit.

Acting as a player in the circular economy by valorizing everything that can be

Beyond the reuse of treated wastewater and the anaerobic digestion of sludge, which are means of aligning water treatment facilities with a circular economy approach, our Research & Development teams also explore the coupling of treatment processes with the creation of new resources. For example, Stereau is studying a valorization pathway for the carbonate pellets produced by its Calcycle® process for water decarbonation. Stereau also offers solutions to address resource scarcity. By recovering nitrogen and phosphorus from wastewater, wastewater treatment plants provide an alternative to the depletion of mineral resources. Furthermore, the Group has been valorizing sludge from wastewater treatment through agricultural use for many years. This approach follows the same logic by providing farmers with a low-cost organic amendment as a substitute for chemical fertilizers.

Focus on three key sludge recovery processes

Stereau's Sonoflux sludge recovery process.


A physical ultrasonic cell lysis process for the pretreatment of biological sludge, SONOFLUX® optimizes the performance of anaerobic or aerobic sludge digestion.  

Digesthane process - Stereau


Sludge reduction and energy recovery process optimizing the performance of conventional anaerobic digestion. The anaerobic digestion process is enhanced and accelerated by ultrasonic sludge pre-treatment.  

Lanodor® process


Biological Treatment of Odors from Wastewater and Sludge Treatment.

Focus on three emblematic sludge recovery projects

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