Anammox, an acronym for ANaerobic AMMonium OXidation, is a microbial process of the nitrogen cycle; it is a process that occurs in many natural environments. There is a huge interest in the application of the anammox process in wastewater treatment.

The practical implementation of this process is currently limited to side-treatment (e.g., warm reject water after dewatering of digested sludge). The concept proposed in this TKI project could be applied for main-stream nitrogen removal via anammox in wastewater treatment, including potential application at lower temperatures.


The project’s aim is to test the anammox process for the removal of nitrogen from municipal and industrial wastewater in main-stream mode in a small, modular membrane bioreactor (MBR), making use of fine screening, online monitoring and remote control.

In phase 1 the research has been conducted at the Simmern WWTP in Germany (until spring 2022).

In phase 2 the pilot will be transferred to an industrial research location in the Netherlands (from spring 2022).


The aim is to treat municipal and industrial wastewater with the anammox process using a small, modular MBR pilot. The first step is to flocculate suspended solids in a reactor, thus binding particles and organic matter, after which a sufficient amount of suspended matter will be removed with a fine screen and cake filtration, before the wastewater stream enters the anammox reactor.

By using a selective removal technique based on size (fine screen), the desired anammox bacteria, which grow in the form of granulates, are separated from unwanted microorganisms from the excess sludge. The separated anammox granulates are then returned to the anammox reactor. The excess biological sludge with the unwanted microorganisms is transferred to the sludge treatment unit.


The anammox process is already used for example to treat reject water at wastewater treatment plants, but at higher temperatures (around 30°C). Application in the main-stream at lower temperatures (10-20°C) presents a major challenge. The desired biological response is a conversion of over 50% of ammonium to nitrate by means of ammonium oxidizing bacteria (AOB), and then the conversion of the remaining ammonium with the formed nitrite by anammox bacteria. However, there is competition for nitrite between anammox bacteria and nitrite oxidizing bacteria (NOB). The retention of active anammox bacteria in a reactor is a challenge, because they grow very slowly at low temperatures.


The activities include the development, design and construction of a fine-screen anammox MBR pilot installation for optimal retention of annamox bacteria for the nitrogen removal. Online sensors and remote control will be implemented to make it also possible to monitor the improvements in the process and to achieve remote control for a decentralized, small and modular treatment facility. Testing, optimization and evaluation of the system will take place at two locations:

a) at the pilot production site in Germany (municipal wastewater);
b) at an industrial wastewater treatment plant in the Netherlands.

This TKI project will result in a tested small, modular anammox MBR pilot installation. State-of-the-art sensors and remote control will be installed to enhance understanding and control of the anammox process. Besides the optimized pilot installation, the deliverables of the TKI project will be a monitoring plan, a public TKI report, probably several presentations at national and international conferences, as well as articles. Moreover, the intention is to organise a technical workshop to present the outcomes of the project.


This project fell significantly behind schedule due to the corona crisis, principally because of delays in the construction and the shipping of the pilot from China. The pilot finally arrived at the site in Germany in the autumn of 2021. Following initial operational tests and start-up, the installation began operating on-site in Simmern in November 2021. The pilot is expected to be transferred to the second research location in the Netherlands in the spring of 2022.

Lay out Anammox MBR pilot plant design.