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Improving the elimination of micropollutants in wastewater-treatment plants

Household wastewater released to rivers is the main source of pollution caused by medicinal residues in aquatic environments. The goal of the Armistiq project, managed by Cemagref with funding from Onema, is to improve techniques in wastewater-treatment plants to reduce the presence in the natural environment of not only medicinal residues, but micropollutants in general.

Wastewater-treatment plants were originally designed to eliminate nitrogen, carbon and phosphorus from water and they manage to remove about 85% of priority substances*, plus up to 95% of certain emerging substances, such as pharmaceutical compounds and cosmetics. However, some 15% of micropollutants resist standard biological treatment and are released by standard treatment plants to the environment. That is notably the case for certain pesticides and medicinal residues such as carbamazepine and various antidepressants.

How can the operation of treatment plants for wastewater and sludge be improved to reduce micropollutants? To find answers, Onema funds the ambitious ARMISTIQ project, managed by Cemagref, Suez Environnement and the University of Bordeaux, to reduce the quantities of micropollutants exiting wastewater-treatment plants. The project is based on the results of the AMPERES research programme which assessed the performance of eight treatment techniques (activated sludge, filters planted with reeds, membrane bioreactors, etc.

A number of potential solutions will be studied. In standard treatment plants, a majority of the 70% of micropollutants eliminated from water are adsorbed by the sludge. The scientists will attempt to improve and enhance the reliability of biological and thermal processes to reduce micropollutants in sludge. In addition, optimal operating conditions for a number of advanced tertiary treatment processes (ozonation, activated-carbon filtering, reverse osmosis) will also be studied during the project. Another field of research involves plant-based techniques that are growing rapidly and have the potential to treat micropollutants while requiring a small environmental footprint.

The project will also carry out technical, economic and environmental assessments and comparisons of the various processes.

* Substances termed "priority" are those listed by the Water framework directive and that must be reduced or eliminated from the natural environment by 2015.

Contact: stephane.garnaud@onema.fr

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