Effect of Storing on Fertilizing Properties of Sewage Sludge

The disposal of sewage sludge may be combined with its economic utilization. It depends on the physical, chemical and microbiological characteristics of the substance and the manner of sludge treatment. Organic, but also inhibiting substances (pathogenic microorganisms, heavy metals, etc.) included in the sludge may determine the manner of its management or disposal, e.g. through agricultural utilization or combustion. In case of agricultural utilization, this manner of sludge management is also influenced by the specificity of agricultural cultivation and periods of the reclamation of agricultural lands. Thus, the problem of periodic storage and the possibility of its effects on changes of sewage sludge properties occurs. The article presents results of research concerning changes of basic fertilizing properties of sludge during its year-long storage in field conditions. The research analysed, among others, changes of the content of organic substance, organic carbon, nitrogen and phosphorus.