Distribution of Heavy Metal Fractions in Sewage Sludge from a Selected Municipal Sewage Treatment Plant

Sewage sludge used for reclamation of egraded areas or in agriculture must have a certain total heavy metal content, as required by law. In practice, however, it is important to carry out a fractional analysis of the elements contained in the sludge. This activity allows to determine the chemical form of a given metal, thanks to which it is possible to assess the assimilability of elements by plants. The study proved that the fraction of certain metals in sewage sludge can vary depending on the period studied. The combination of elements with other compounds in sludge from one treatment plant can vary from month to month. Once analysis has been carried out, it should not be the basis for assessing the bioavailability of metals if sludge from a given treatment plant were to be sampled several times a year.