![]() In literature it can be defined as by-product, yet it shall be treated as a waste in the process of wastewater treatment. Sewage sludge can be defined as the solid or semi-solid residue left over after the treatment of wastewater. Nowadays there are several papers focusing on new serious threats to human health and ecosystem occurring in sewage sludge – both chemicals (such as toxic trace elements – Se, Ag, Ti nanoparticles polyaromatic hydrocarbons polychlorinated biphenyl perfluorinated surfactants, polycyclic musks, siloxanes, pesticides, phenols, sweeteners, personal care products, pharmaceuticals, benzotriazoles) and biological traits ( Legionella, Yersinia, Escherichia coli O157:H7). In this paper, a review on quality of sewage sludge based on the publications after 2010 has been presented. The Sewage Sludge Directive (86/278/EEC) regulates the allowable limits of Zn, Cu, Ni, Pb, Cd, Cr and Hg and pathogens and allows for recovery of sludge on land under defined sanitary and environmentally sound conditions. For over decades, a great deal of attention has been focused on total concentration of few heavy metals and pathogenic bacteria Salmonella and Escherichia coli. This situation occurs mainly due to the fact, that the sewage sludge may contain a dangerous volume of different contaminants. However, according to the report of European Commission published in 2010, only 39% of produced sewage sludge is recycled into agriculture in the European Union. As sources of nutrients (C, N, P) they are widely used in intensive farming where large supplementation of organic matter to maintain fertility and enhance crop yields is needed. Sewage sludge/biosolids are by-wastes of municipal and industrial wastewater treatment.
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