Sewage sludge/biosolids are by-wastes of municipal and industrial wastewater treatment. 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. 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. This situation occurs mainly due to the fact, that the sewage sludge may contain a dangerous volume of different contaminants. 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. 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. In this paper, a review on quality of sewage sludge based on the publications after 2010 has been presented. 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).
Supravital species identification of morphologically similar syntopic earthworms inhabiting dung and compost heaps or those from commercial cultures is difficult. The aim of the studies was to find out non-invasive species-specific markers for proper segregation of earthworm species from a dense mixed colony of waste decomposers. Worms were segregated according to external characteristics into Eisenia andrei, Eisenia fetida, and Dendrobaena veneta, and left for reproduction and analysis of non-invasively retrieved coelomocyte-containing coelomic fluid and/or species-specific partial sequences of cytochrome c oxidase subunit I (COI) gene in DNA extracted from amputated tail tips of adults and their offspring. Flow cytometric analysis of coelomocyte samples revealed that amount of nuclear DNA increases in order D. veneta ≪ E. andrei < E. fetida, and intensity of eleocyte-derived fluorescence is lower in D. veneta than in Eisenia spp. Spectrofluorimetry of coelomocyte lysates revealed that the amount of eleocyte-stored riboflavin is significantly lower in coelomocyte lysates from D. veneta than from Eisenia spp., and the emission peak of X-fluorophore is much more distinct in D. veneta than in Eisenia spp. Coelomic fluid of E. andrei exhibits a very distinct spectra of MUG fluorophore which are absent in D. veneta and in the majority of E. fetida, while some E. fetida possess MUG-like fluorophore. Sequences of the COI gene in the DNA of the worms from the mixed colony and their offspring confirmed species identity. In conclusion, species-specific coelomocyte-derived markers may be a useful complement to morphological and DNA-based taxonomy during studies on syntopic earthworms.
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