The ion exchange membrane bioreactor (IEMB) is a hybrid process allowing safe treatment of groundwater contaminated with high concentrations of perchlorate, as was found in the Israeli coastal aquifer. Perchlorate is removed from the water using an anion exchange membrane (AEM) into a biological reactor where it is used as an electron acceptor under anaerobic conditions. The AEM acts as a barrier and keeps both compartments completely separate. Possible inhibitions of perchlorate bio-reduction are competition for electron acceptors (nitrate for example), and the dynamics of the different species comprising the overall populations in the bioreactor part of the IEMB.
In this study, we found that glycerol is a suitable carbon/electron source for biodegradation of perchlorate in the IEMB. The enriched culture in the bioreactor contained both glycerol fermenting species such as Klebsiella oxytoca and perchlorate reducing species such as Dechloromonas sp and Alicycliphilus denitrificans. It was not clear however, if these populations interact through cross feeding or act independently of each other. During IEMB operation with perchlorate and glycerol most of the activity was concentrated in a biofilm attached on the inner part of AEM. This biofilm increased the flux of perchlorate through the AEM. We further found that the presence of nitrate, even at high concentrations, does not hinder the biodegradation of perchlorate. The presence of a denitrifying and perchlorate reducing organism such as Alicycliphilus denitrificans may explain this observation. In conclusion, biological treatment approach combined with membrane separation technology, with high potential for application in the field.
