Biogranules developed in the upflow anaerobic sludge blanket (UASB) re
actors were analysed by Xray spectrometry for the local concentration
of individual inorganic elements and by X-ray dot mapping for the pict
orial distribution of these elements in the cross-section of the biogr
anules. This information is of significance for the understanding of t
he sludge granulation mechanism and the role of inorganic elements.