The groundwater from over 200 wells in Donauried and from the deep well at Burgberg can be delivered directly as drinking water due to its good quality; only some of it is softened in a decarbonisation plant at Langenau waterworks. However, accidents or traces of micropollutants may severely restrict use of the groundwater for the public drinking water supply. In order to be well prepared for possible scenarios at any time, the Landeswasserversorgung ommissioned a groundwater filtration plant at Langenau waterworks in 2014.

The spring water from Buchbrunnen spring is of excellent quality by nature. Only after prolonged heavy rain and during snow melting does mineral turbidity occur in the spring water. With the construction of the A7 federal motorway through the water protection area of Buchbrunnen spring, the treatment plants at Egau waterworks had to be expanded between 1982 and 1984 for preventive protection of the drinking water quality.

The ground and spring water reserves used by the Landeswasserversorgung are fed from the karstified Jura mountains of the Swabian Alb region. Because of the long period for which the water is underground, the seeping precipitation water absorbs many minerals and particularly limestone on its way. The groundwater transported in Donauried naturally displays an average total hardness of 22 degrees of German hardness; the average values in Egau waterworks are 18.5 degrees of German hardness.

A large proportion of the drinking water delivered is used as service water. The water hardness plays a major role here in the heating of the water, due to the mostly undesirable deposit processes, or in the measuring of detergents. To satisfy the desire for softer water and benefit from the economic and ecological advantages of central drinking water softening, Langenau waterworks has a central decarbonisation plant. It is therefore possible to deliver the groundwater extracted from Donauried to the customers as drinking water at 13.0°dH (hardness range average). After the positive experiences at Langenau waterworks, a decarbonisation plant was also constructed at Egau waterworks. There, the karst spring water is softened to 13.0°dH.

The plants for extraction of drinking water from the river water of the Danube specifically comprise an untreated water pumping station that takes the water directly from the river, a pressure pipe from the pumping station to Langenau waterworks, and the treatment plants at the waterworks. At peak times, up to 2,300 litres of Danube water per second can be processed into drinking water. The process for drinking water extraction from the Danube has been investigated and optimised over many years of trials.

It essentially comprises the following process steps:

1. Preliminary cleaning using flocculation sedimentation to reduce undesirable substances in the water, such as substances causing turbidity or humins, but also trace substances in the untreated water
2. Ozonation for oxidative removal of organic and inorganic substances and to disinfect the water
3. Flocculation filtration via multi-layer filters to remove the remaining suspended substances
4. Activated carbon filtration to remove organic pollutants in minimal concentrations
5. UV disinfection as a safety barrier to deactivate microorganisms
6. Addition of chlorine dioxide to protect the drinking water from microbiological influences on the way to the customer