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Next to nitrogen and potassium, phosphorus is the major element essential for the growth
of plants, development as well as for the existence of living organisms. Therefore, in the last
decade the demand for the phosphate fertilizers has increased by over 20%. The leading producer
of this precious material is China, which secures up to 40% of the total world’s needs.
Municipal and industrial wastewater as well as sewage sludge generated in its treatment
process constitute significant sources of phosphorus. Phosphorus contained in sewage sludge may
occur in the form of I-, II- and III- nivalent, divalent and trivalent metal salts, mainly in the form of
salts of magnesium, calcium, iron and aluminium. The tests referring to the occurrence of
biologically active forms of phosphorus in sewage sludge play the key role in the assessment of the
actual amount of phosphorus that can be released from sewage sludge. The analysis of the
changes of concentration of particular forms of phosphorus allows to determine their role in the
process of this element release from sewage sludge into water. This kind of information can be
obtained by means of application of the speciation process.
While testing sewage sludge generated in « Hajdów» Wastewater Treatment Plant two
methods of fractionation of elements in soil and bottom sediments were applied, namely the BCR
and the Williams method. The tests consisted in the analysis of phosphorus speciation in the
preliminary, excess and digested sludge. The share of particular fractions of phosphorus
was determined in each of the sludge type. The tests carried out with the use of BCR and
Williams methods proved that the distribution of particular fractions of phosphorus may be
variable. Comparing the share of the mobile fraction and biologically accessible fraction it was
proved that their amount changes depending on the sludge type and the processes applied in the
wastewater treatment.
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