ABSTRACT
Cyanobacteria form mass occurrences in raw water sources of waterworks and may represent a health hazard to water consumers by production of potent hepatotoxins, microcystins. The aim of this study was to assess the fate of microcystins in artificial recharge of groundwater. Laboratory experiments with hepatotoxic Microcystis and Anabaena species showed that cyanobacterial cells were efficiently removed by filtration through soil and sediment columns. However, in soil columns the removal of microcystins was less efficient than the removal of biomass. In sediment columns the biodegradation of microcystins was rapid. In field studies at two bank filtration sites in Finland traces of microcystins, usually below 0.1 µg l-1, and single cells or filaments of cyanobacteria were occasionally detected in observation tubes and pumping wells of the waterworks. The isolated bacteria capable of degrading microcystins have all been aerobic and therefore the anaerobic conditions common in bank filtration zones probably hinder degradation of microcystins.
