Issues of biological and agricultural treatment of municipal sewage sludge

Increase of sewage sludge production in Poland requires undertaking specific methods for their utilization and disposal. The reason is that sewage sludge, in addition to being rich in organic matter, and biogenic compounds such as nitrogen and phosphorus, which are beneficial from an agricultural point of view, also contain heavy metals, toxic organic pollutants such as persistent organic pollutants and polycyclic aromatic hydrocarbons, inorganic compounds such as silicates and clay, and pathogenic bacteria and other microbial contaminants. This implies problems with further use of such polluted sludge as fertilizer in agriculture. The aim of this paper is to analyze the possibilities and limitations of natural management of sewage sludge, taking into account their effects on the restoration and conservation of organic matter in the soil and the yielding of plants. In addition, the main methods of treatment of polluted sludge before introducing it into the environment are considered.