Biological treatment of RO concentrate

Reverse osmosis (RO) is a water treatment technique that involves the use of semi-permeable membranes to remove unwanted molecules and particles. It is an effective way of extracting a wide variety of different contaminants from different types of water and it is being used increasingly for drinking water production. One of the drawbacks of RO is that it releases a concentrated residual stream containing a wide variety and high concentrations of pollutants, making it difficult to comply with discharge requirements. The biological treatment of RO concentrate could represent a possible solution for the more widespread and sustainable use of this method.

Biological removal of ammonium from RO concentrate

Ammonium (NH4+) is one of the contaminants left in the residual stream during reverse osmosis. Anammox bacteria is a potential option for the removal of this ammonium from the RO concentrate. Anammox stands for ‘Anaerobic Ammonium Oxidation’ and it could be a sustainable and cost-effective approach. However, low temperatures (<15 °C)) and low ammonium concentrations (<25 mg/L) in drinking water sources are a challenge for these bacteria. The present project is investigating whether anammox bacteria that have been adapted to these conditions can be used for this purpose.


This project is an alliance between KWR and the Department of Microbiology at Radboud University Nijmegen. It is a four-year PhD project with the drinking water companies as a user committee consisting of Waternet, WMD, Dunea and Oasen.