The Fate of the Cyanotoxin Dihydroanatoxin-a in Drinking Water Treatment Processes

Only recently has the cyanotoxin dihydroanatoxin-a (dhATX-a) been detected more frequently in different surface waters, some of which are used for supplying drinking water. As data about the fate of dhATX-a in drinking water treatment processes are still scarce, the present study investigated the behavior of dhATX-a in different water treatment steps: slow sand filtration, flocculation, adsorption onto activated carbon, ozonation and chlorination. The almost complete removal (>95%) of dhATX-a was observed in sand columns simulating slow sand filtration without showing a long adaptation phase. The results further indicate that dhATX-a can be removed using powdered activated carbon at dosages of 50 mg/L with removal rates between 75 and 93% and also by using ozonation with dosages above 1 mg/L at a concentration of ca. 4.5 mg/L background organic carbon. In contrast, no elimination of dhATX-a was observed in flocculation and chlorination experiments.