Once waste waste water is sent to a waste water treatment plant, it can be discharged into the natural environment or re-used for gardens, irrigation or industrial use.
Providing waste water treatment facilities that can discharge treated wastewater into the natural environment is a priority. SUEZ has an overall and comprehensive offer for this, ranging from technical reviews to the completion of facility refurbishment works, by way of new waste water treatment facilities.
Water is a reusable resource, either in agriculture through irrigation or in industry or urban operations, such as providing water for fountains, street cleaning, etc. Recycling waste water keeps pollutants from being released into nature through the use of innovative techniques such as ultra-violet treatment, reverse osmosis or membrane filtration.
As the end-product of wastewater treatment, sludge is a major economic and environmental concern. SUEZ provides its customers with a wide range of processes from digestion to incineration, thickening, dewatering, composting or drying. The aim is to reduce the volume of sludge produced, but also to reuse it for agricultural purposes and to recover its energy potential in the form of biogas.
Once dried, sewage sludge can also be recovered for energy. Since the sludge produces biogas, it is an alternative to fossil fuels (oil, gas, coal) and its calorific value is comparable to wood.
Among the solutions the Group offers is a pyrolysis gasification process, in which gas and fumes from sludge provide heat. The SIAAP Seine upstream plant in Valenton (France), which has a processing capacity of 4.6 metric tonnes of dried sludge per hour, uses this innovative process to recover 60 GWh/year of thermal energy. Renewable energy can be produced with sludge methanisation, as is done at the Grande Synthe sewage treatment plant in Dunkirk.
The Group provides innovative and economical solutions for eliminating the sludge produced by wastewater treatment, with the help of thermal treatments.
This was done on the site of the wastewater treatment plant in Gdansk, Poland, where the combination of incineration furnaces and pre-drying reduces fuel consumption efficiently. The energy recovered from the fumes in a heat exchanger is used to preheat the sludge. This coupling of pre-drying and heat recovery from fumes significantly reduces CO2 emissions. Since its installation, the process has resulted in savings of €1 million per year and helped eliminate 6,800 metric tonnes of greenhouse gas emissions (CO2 equivalent).