Examples of approaches and technical solutions specific to the water treatment plant

1) Optimisation of the energy loop: installation of exchangers in order to recover the maximum amount of energy possible; digestion of sludge to produce biogas. Biogas is co-generated, and is used as a substitute for heating oil in boilers and the incinerator. The project currently underway aims to transform the biogas into biomethane and to inject it into the gas grid; this would make it possible to supply 5,000 low-energy consumption households. In the short term, the sludges will be autothermally digested and the whole sludge chain will be carbon-neutral.

2) Treatment of residues: residues from dehydration are highly concentrated. They are therefore treated in a specific unit with a capacity of 60,000 inhabitant equivalents, so as not to overload the water treatment plant. This unit comprises an anoxic tank, an aeration tank for biological treatment and a flotation tank to extract the sludge produced. Treated residues are sent back to the water-treatment cycle.

Summary of the skills and expertise that can be seen on the site

Skills that can be seen on the site relate to the entire treatment process for wastewater and by-products: pre-treatment (three levels of rake Screens, silt and grease traps); water treatment (primary settling tanks, aeration tanks with nitrogen and phosphorus treatments, clarifiers); sludge treatment (thickeners, digesters, centrifuges, sludge incinerator, smoke treatment).

Key figures

Activated sludge prolonged aeration water treatment plant
Fourth largest water treatment plant in France, with a capacity of 1,000,000 inhabitant equivalents, amounting to 61 tonnes of DBO5/day and a hydraulic capacity of 240,000 cubic metres per day and up to 380,000 cubic metres per day in rainy weather
81 million cubic metres of water treated in 2013
Start-up in 1988, compliance work begun in 2005
100% compliance with standards for discharge of purified water – 91.2% efficiency, all parameters taken together
100% compliance for incineration emissions
99.9% of by-products recycled
1.9 million cubic metres of biogas produced in 2013

Main stakeholder

Communauté Urbaine de Strasbourg

1 parc de l'Etoile 67076 Strasbourg

Players involved and their roles

Communauté Urbaine de Strasbourg