Case Study Anammox

A success story starring scientists and technology experts

This case study describes the discovery of anammox bacteria and their application in a novel way of wastewater treatment. This story started in 1977, when the Austrian scientist Engelbert Broda predicted the existence of microorganisms that could make a living out of the conversion of ammonium and nitrite to dinitrogen gas: ANaerobic AMMonium OXidation (anammox). However, it took a while before his predictions were confirmed. In the early 90s anammox bacteria were discovered in a wastewater treatment plant at the Dutch company Gist Brocades in Delft. Since this discovery lots of studies at mainly the TU Delft and Radboud University in Nijmegen focused on the functioning of these bacteria and their presence in both wastewater treatment plants and the environment.

Anammox bacteria appeared to be very good at removing nitrogen compounds from their environment, making them interesting in the field of wastewater treatment. The anammox process had many advantages over the traditional process: The energy usage can be reduced up to 60%, CO2 emissions are reduced by up to 90%, there is no need of adding external carbon sources (like methanol) to clean our wastewater and the anammox process has a much smaller footprint (up to 50% less reactor volume).

To apply the anammox process, the Universities of Delft and Nijmegen worked together with three external partners. The first partner was Paques, a Dutch company that focuses on anaerobic wastewater treatment. Secondly the Water board Hollandse Delta joined in, one of their municipal treatment facilities is located in Rotterdam and treats wastewater from almost half a million households. STOWA (the Foundation of Applied Water Research) was the third partner; a knowledge center of regional water managers. This consortium transferred the results from lab scale (10 Liter) to a 7,000-fold bigger full scale application located in Rotterdam. This large investment project started in 2002 and was sponsored by the European Union.

One of the big challenges for full scale application was the enrichment of anammox bacteria. After a start-up period of two years, full operation conversions could be reached with a maximum removal rate of 750 kg nitrogen per day. During this start-up phase the communication between scientists and technology experts was crucial.

In the last 20 years scientists have optimized growth and development in reactor systems; nitrogen removal efficiencies increased and improved treatment facilities were designed. Currently, treatment plants using the anammox technology are constructed worldwide. The largest plant was built in China (Tongliao Meihua Biological Sci-tech Co., Ltd.), containing a 6700 m3 bioreactor filled with bright red anammox bacteria. This is 95 times bigger than the first full scale application in Rotterdam, with a start-up period of only two months.

The anammox process is nowadays successfully used for the removal of ammonium from different sources of wastewater and as well for the removal of ammonia from waste gases. Thanks to the broad application range and teamwork combined with patience during the start-up period of the first full scale bioreactor, the anammox process has become one of the leading nitrogen removal strategies in wastewater treatment.