Researchers in Germany have successfully removed ammonia from wastewater using a new process.

For this, researchers at the Institute of Chemical Engineering at Ulm University built a pilot plant in cooperation with the Steinhäule Wastewater Treatment Plant Association.

The test facility at the Steinhäule wastewater treatment plant in Neu-Ulm removes ammonia from sewage sludge. Image: Christine Liebhardt / University of Ulm.

“We are very proud to be supporting our municipal partner in the development and construction of this pilot plant and thus generating significant added value for our region,” said Professor Thomas Grützner from the Institute of Chemical Engineering.

“The process developed by the researchers will now be tested on-site at the Steinhäule wastewater treatment plant for several months in order to later scale it up to an industrial level.” 

Ammonium is toxic

The team also revealed that ammonium is toxic to fish, and the nutrients stimulate the growth of algae and aquatic plants. The water becomes cloudy and loses oxygen, leading to a loss of biodiversity.

To prevent this so-called eutrophication of waters, among other things, the European Union has adopted a new Urban Wastewater Directive: From August 2027, it obliges municipalities to remove significantly more nitrogen and phosphorus from their wastewater treatment plants than before. Some of this nitrogen is present in the wastewater as ammonium. This is where a project at the Institute of Chemical Engineering at the University of Ulm comes in, according to a press release.

Since May 2026, this new system has been undergoing testing at the Steinhäule wastewater treatment plant in Neu-Ulm. It is operated by the Zweckverband (special-purpose association) of the same name. 

Future-proof technologies

“The ZVK (Zweckverband Abwasserbehandlung Steinhäule – Steinhäule Wastewater Treatment Plant Association) has a strong interest in the use of future-proof technologies in all areas of the treatment plant, especially those aimed at sustainability, resource efficiency, and the circular economy,” said Jonathan Fuchs, head of operations and Laboratory at the Zweckverband Abwasserbehandlung Steinhäule, regarding the co-operation with the University of Ulm.

The plant concept is based on steam stripping, a special type of thermal separation technology in which steam absorbs a volatile component from a liquid. In a column – simplified as a vertical tube – so-called centrate water, which is produced during sewage sludge dewatering and is heavily loaded with ammonium, is passed countercurrently to the rising steam.

The centrate from the digested sludge is heated to boiling conditions by the rising steam. During this process, the originally bound ammonium passes into the gas phase as ammonia and is carried upwards out of the plant by the steam, as per the release.

The research team revealed that at the bottom of the column, the purified centrate emerges, containing only small amounts of ammonium. The steam exiting at the top, including the ammonia it contains, is condensed.

A portion of the condensate is returned to the column to concentrate the ammonium content in the condensate. The remaining part of the condensate can, if necessary, be further concentrated in an additional step – thus producing concentrated ammonia water in the end.