Water Filtration

Biochar (Activated Carbon) Used in Water Treatment Systems to Remove Micropollutants

According to the Swiss Federal Office of the Environment (FOEN), the quality of surface waters has improved considerably since the 1970s. Toxic substances have disappeared or were banned. However, inputs of micropollutants (trace compounds) are posing an increasing challenge for the protection of bodies of water. This is due, on the one hand, to the daily use of a large number of these compounds and, on the other hand, to the fact that even low concentrations of micropollutants can cause damage to aquatic organisms. According to current knowledge, the concentrations detected in surface waters do not harm human health. However, various studies clearly suggest that pesticide pollution is a key factor influencing the widespread lack of species diversity observed in bodies of water.1

Of the many pilot projects conducted in German speaking regions and the advanced methods of purification realised to date in municipal sewage treatment plants, the use of ozone and of activated carbon have proven feasible for the targeted elimination of micropollutants. These two process technologies can remove a wide range of micropollutants from waste water to a comparatively large extent. In addition, they are easy to integrate into the existing purification process of a sewage treatment plant. Both process technologies require an additional downstream stage to post-treat the waste water subsequent to the “micropollutants stage”. When using powdered activated carbon, this additional stage removes the powdered activated carbon particles that are laden with micropollutants to the greatest possible extent and, when using ozonation, it removes the resulting degradation/transformation products.2

The above cited source indicates average specific costs for the removal of micropollutants for Germany in a range of 0.10 to 0.15 EUR/m3 of treated water, including the additional downstream stage for the removal of the charcoal or of the metabolites of the ozone process. The study projected that, in 2014, a total of EUR 1.3 billion would have been required to remove the micropollutants from all medium to large sized sewage plants in Germany. If we assume that 10% of this annual cost would be allocated to purchase the activated carbon necssary, an annual activated carbon market of EUR 130 million would come into being to supply Germany alone for the micropollutant removal from sewage.

If large scale micropollutant filtration comes into being, as seems likely from the EU directives on the matter, research should be undertaken to find the best further use for the used activated carbon.