Phytoremediation as a method for cleaning sludge beds of biological treatment plants from heavy metals

The aim of this study is to select a phytoremediation plant for cleaning sludge beds of biological treatment plants from heavy metals. The study was conducted on sludge beds of biological treatment facilities of Veliky Novgorod with a sludge retention time of 1 year and 15 years. It is established that the forms of metals in the sludges and wastewater sludge depend on the nature of the metal. Manganese (II) predominantly binds to compounds that make up sludge and wastewater sludge by the ion exchange mechanism, copper (II) - by the complex formation mechanism, zinc (II) - is codeposited with calcium and magnesium carbonates, manganese (IV) and iron hydroxides (III). Six selected plants were analyzed (bedstraw, cow vetch, field daisy, silverweed cinquefoil, base vervain, winter cress), those growing on sludge beds with a sludge retention time of 15 years, for the content of copper (II), zinc (II) and manganese (II) in different parts of plants. The phytoremediation plant was selected according to the indicators of the coefficient of biological accumulation (coefficient of biological accumulation) and translocation factor. It has been established that the bedstraw can be called a universal phytoremediation plant, in the absence of significant sludge contamination with copper (II), it is most preferable to use base vervain. Selected phytoremediation plants can be used for artificial planting on sludge beds in order to further use these beds as fertile lands.