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Energy from waste water

Renewable energy for the production of heat and cold

Over 50% of the global energy requirement is used for heating and cooling, including hot water treatment. In households, the proportion is even 73% of the total energy consumption – to date, CO2-critical energy sources have been used almost exclusively.

The previously largely unused wastewater is available as a renewable energy source all year round, around the clock. The temperature in the canal is between 12 and 18 °C all year round and is therefore higher than the temperature of the outside air, geothermal energy or groundwater even in winter. If there is a company nearby, the temperature of the waste water can rise to up to 30 degrees.

Studies show that up to 14% of the required heat demand can be covered from the energy source waste water. In addition, there is the enormous and steadily increasing need for cold, which can also be generated from waste water energy. This makes an important contribution to the decarbonization of the heating sector.


Where and how is energy from wastewater used

Wastewater heat can be used in many ways for heating and cooling objects as well as for preheating fresh water. Depending on the location of the energy connection, we distinguish between:

In-house applications

  • Fresh water preheating
  • Installation of heat exchangers in the building BEFORE the sewer – if necessary in combination with heat pumps

Channel applications

  • Heating and cooling of buildings and fresh water preheating
  • Connection to local and district heating and cooling networks
  • Installation of heat exchangers in the duct or externally (bypass solution) in combination with heat pumps

Energy hub sewage treatment plant

  • Heating and cooling of buildings at the sewage treatment plant and fresh water preheating
  • Connection to local and district heating and cooling networks
  • Use of waste heat for sewage sludge drying
  • Installation of heat exchangers in the clarifier or in the receiving water in combination with heat pumps

Sewer wastewater energy for heating & cooling of buildings and hot water production

The technology for generating energy from wastewater is simple and tried and tested. The heart of the system is formed by innovative heat exchangers, with which the energy is obtained from the waste water, as well as special waste water heat pumps, which make the energy usable for heating and cooling larger buildings. In summer, waste water energy systems can also be used for room cooling. The heat pump works in the “reverse” way as a chiller.

Essential requirements are:

  • Sufficiently large duct, DN 400 or larger
  • Available waste water quantity > 10 l/s
  • Temperature > 8°C
  • Proximity of consumers to the duct (depending on the temperature level in the duct) maximum distance 900 m
  • Demand for heating load/cooling load > 50kW
  • Coordination with or approval of the channel operator

More information about the technologies can be found here!

Grafik inklusive Erklärung

Wastewater energy for freshwater preheating

The warm waste water is routed through an innovative heat exchanger in front of the sewer in the building. The waste heat is given off to the “cold” fresh water. This is preheated from an initial temperature of around 10°C to around 26°C and immediately fed to the hot water boiler, where it is heated to the final temperature of around 60°C.

  • Power range 10kW – 100 kW
  • Available amount of waste water at least 3 m3 per day
  • Wastewater temperature ideally 30°C or higher

This technology is therefore ideal for companies with high hot water consumption, such as canteens, baths, dairies, breweries or meat processing companies. More info can be found here!

From the idea to implementation

Energy from wastewater projects are not “off the peg” solutions. It requires detailed planning right from the start and the training of all relevant stakeholders. Rabmer accompanies this process from start to finish.

  • idea generation
  • potential analysis
  • feasibility study
  • project implementation
  • operation of the plant


As part of our membership in act4.energy and the Thermaflex Green Energy Lab as well as well-known associations and networks, we develop innovative solutions for industry, commerce and municipalities.


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Well-known projects and references

Vienna Canal Blumental

The newly built headquarters of Wien Kanal heats (161 kW) and cools (530 kW) with energy from waste water via heat exchangers and heat pumps. Realization 2021.

Office building Vienna Canal

Wien Kanal Blumental – heating (200 kW) and cooling (275 kW) with waste water energy based on Thermliner (Uhrig). Realization in 2017.

Office building ENVIRON

Heating and cooling of an office building in Rheine (DE) with wastewater energy
Operation with 110 kW power (400 kW potential) based on Thermliner
(company Uhrig)

More info

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