In order to prioritize water conservation measures in a targeted manner, Audi uses a site-specific water value that puts the water withdrawal at the locations in relation to regional availability. Taking the regional circumstances into account allows measures to be implemented in areas where water is particularly valuable. This way, the ecologically weighted water consumption in production is to be reduced from the current average of around 3.75 cubic meters to around 1.75 cubic meters per produced car by 2035.
Audi México is a pioneer when it comes to the economic use of water as a resource. The plant is the first production site worldwide to produce vehicles without any wastewater and has been doing so since 2018. A biological treatment facility with a downstream ultrafiltration and reverse osmosis system collects the wastewater generated in production, purifies it, and feeds large quantities back into the plant’s water cycle. The location uses the treated water as service water, reuses it in production, or uses it to water the green spaces on the plant premises, for example.
At the Neckarsulm site, a closed water cycle is to be established between the plant and the neighboring municipal treatment facility of the Unteres Sulmtal wastewater association. Before the cycle and the associated construction of a new water supply facility can start, Audi is testing the procedure with a pilot facility. The water that returns from the treatment facility is fed into a container in the northern part of the plant premises, where it is treated for reuse in production by means of filter systems and membranes. The water quality is checked continuously throughout this process. The quality control also includes a laboratory analysis that determines the properties of the treated water every two weeks. If the tests are successful, construction of the new water supply facility is to start in 2022, and the plant is to close this water cycle from 2025.
A new service water supply center has been in use at the Ingolstadt site since 2019. Together with the previous treatment system, roughly half of the wastewater generated at the location can be fed into a circuit where it is treated and prepared for reuse. The facility treats the wastewater in three stages before it can be reused as service water in production. It first passes through a chemical/physical facility that neutralizes alkaline and acidic elements and removes heavy metals, before entering the membrane bioreactor, the core of the service water supply center. This is where the production water is mixed with sanitary wastewater, and organic components are removed. First, any remaining salts are transferred out via reverse osmosis. The purified wastewater is then reintroduced into the water cycle as process water. By doing this, Audi saves up to 300,000 cubic meters of fresh water per year.
In addition, Audi uses rainwater retention basins at multiple sites in order to cover its own water demand in the most resource-saving way possible. There is a water reservoir with a capacity of 240,000 cubic meters on the plant premises of Audi México. It fills up during the rainy season that lasts for around six months from May to October. The rainwater that is collected and treated is used in the plant. Audi also collects rainwater in underground rainwater retention basins at the Ingolstadt site in order to feed it into the water cycle in the plant as process water. Depending on the weather conditions, up to 250,000 cubic meters of rainwater can be used annually. The use of rainwater is also to be increased at the other locations over the next few years.