Transformation of inherent groundwater and Wyoming type bentonite microorganisms and their efferts on structural iron

The aim of this study was to find out if microorganisms inherent for bentonite or repository site anoxic groundwater are able to affect the bentonite structural iron in conditions that simulate nuclear waste geological repository in anoxic and oxic conditions but favor microbial activity with low bentonite density. The change in the structure of the indigenous microbial communities and their effects on the bentonite structural iron were studied over five years. The dissolving organic carbon from the bentonite was able to maintain the microbial activity only for less than two years. Addition of short-chained organic compounds as electron donors (Na-acetate and formate) reactivated the microbial communities. At the end of the experiment, purified part of the bentonite showed total iron reduction.