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Degres BleusDegres Bleus

Waste water flowing in a sewage system with its average annual temperature of 15°C is an excellent source of thermal energy available at the heart of cities. Degrés Bleus [blue degrees] recovers this energy and in conjunction with modern heat pumps transfers it to where it is needed to provide space heating & cooling, domestic hot water as well as process heat. The solution operates as a closed-loop system, meaning that the dirty water never touches the clean water.

The core of the Degrés Bleus innovation are ultra-thin, stainless steel modular heat exchangers (collectors) set in the invert of the pipes. The collectors come in different shapes and sizes to meet the needs of every individual sewage situation and may be installed both in existing and new pipes offering additional benefit of protecting the pipes’ base from abrasion.

Modular design of the solution, enables quick assembly, scalability, installation and the flexibility to meet various heating demands starting from 800 MWh annually. The Degrés Bleus is ideally suited for buildings, premises and swimming pools with significant and relatively stable heating patterns and may be integrated with various heating systems.

With over 15 references in France, the Degrés Bleus innovation has proven to be a robust and low-maintenance solution delivering number of environmental benefits, such as CO2 emissions reduction by up to 70%.


Warm wastewater from kitchens, showers and toilets is collected from individual properties and carried via drains to sewers, which then transport it to wastewater treatment plants for purification. Thus it is the big trunk sewer pipes that carry high and relatively stable flows throughout a year.



The heat exchanger is installed in the invert of the sewer pipe. Made of stainless steel plates, it is filled with a heat transfer fluid (HTF). The HTF recovers heat from the warmer wastewater and transfers it to a heat pump via a closed circuit. The heat pump boosts the recovered heat to useful temperatures and transfers it to building’s heating and domestic hot water circuits.


  • Cooling and heating solution tailored to clients’ needs
  • Quick & easy installation of heat exchangers via manhole
  • Easy Operation & Maintenance
  • Robust solution that lasts for decades
  • Modern technology enjoying recognition among its users
  • Innovative, proven technology

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