Automobile production needs water. In order to protect this precious resource, Audi will soon be working almost entirely with recirculated service water. This means that the plant will further reduce its consumption of fresh water and generation of waste water.
Water is the source of all life. 70 percent of the earth is covered with it, yet only one percent is available as fresh water. There is good reason why water is also known as ‘blue gold’. Audi understands the importance of this resource – water-saving processes at the Ingolstadt plant are being continuously improved through the use of a membrane bioreactor (MBR).
In future, waste water will be processed in two stages inside the reactor on the factory site. First, bacteria clean the water. They break down organic pollutants like paint solvent, while inorganic pollutants like heavy metals – such as nickel and zinc – attach to their surface and are thus retained. In a second step, membranes prevent the bacteria from entering into the waste water. “This socalled ultra-filtration doesn’t occur in conventional purification plants. We use membranes with permeability below the micrometer level. They are so fine that they present an absolute barrier to bacteria and viruses,” explains Dr. Antje Arnold from Operational Environmental Protection. “The processed waste water is of a very high quality and can then be reused as service water.”
MBR technology is reducing the annual consumption of fresh water for production in Ingolstadt by up to 40 percent – saving 500 million liters. The proportion of waste water is set to sink by up to 50 percent and hazardous waste by up to 20 percent. This marks a clear competitive advantage for Audi: “No other automaker worldwide is using a membrane bioreactor to recirculate water,” underscores Arnold. Initial tests with a small test system have already been delivering successful results for several months. The large system is currently in the planning stages, with the new technology scheduled to enter service officially mid 2014.
Membrane bioreactor (MBR)
Combination of two systems
Audi is continuing systematically with its energy-efficient and conservational approach to water as a resource.
Two different grades of water are currently in use at the Ingolstadt plant – drinking water is used only where absolutely necessary, such as in employee shower rooms. Service water is used for everything else. Audi draws its water from sources such as the Lepsinger Springs and the site’s own karst spring. But the supply from these sources is limited. Because the plant’s need for service water and cooling is set to increase in the coming years due to new buildings, Audi is securing its ecological water supply for the future with the introduction of the membrane bioreactor.
A further proportion of service water comes directly from the skies – rain water is collected from 450,000 square meters of roof and car park surface and piped into five reservoirs and two storage channels. The water can be drawn off at any time as required.
In order to allow some of the service water to be reused, it is purified in a processing plant. “We want to achieve the best possible quality,” stresses Gerhard Scharrer, who is responsible for water and waste water analysis at the Ingolstadt plant. The graduate engineer monitors all processes throughout the water circulation system. First, dirt particles are removed from the used service water in several stages, after which the ph level is adjusted. The water is then circulated back to production via a pumping station at the water works. “Then the circuit starts again from the beginning. We process our service water this way round the clock,” says Scharrer.
If you include the cooling circuit with its annual turnover of almost 36 million cubic meters in the calculation, 95.8 percent of water used in Ingolstadt remains within the plant’s circulation system. With the new membrane bioreactor, this proportion is set to rise to 97 percent. A very good perspective, as far as Antje Arnold is concerned: “We are already operating extremely sparingly and sustainably with our water. With the membrane bioreactor, we are taking the next major step toward zero waste water production.”
Germany´s water footprint
The water footprint indicates the amount of water evaporated, consumed or polluted during the manufacturing processes of all products and services used in a country. The German people consume 160 billion cubic meters of water every year – equating to three times the volume of Lake Constance. Every single inhabitant consumes directly and indirectly 5,288 liters per day. Around 50 percent is attributable to the water expended importing food and industrial goods from around the world.
(Source: WWF Germany)