Ecological risk assessment of sewage sludge from municipal wastewater treatment plants: a case study

Identification of the Chemical Forms of Heavy Metals in Municipal Sewage Sludge as a Critical Element of Ecological Risk Assessment in Terms of Its Agricultural or Natural Use

“…Taking into account the high environmental pollution and diversity of industrial sectors in the study area, the content of these elements in the sewage sludge probably resulted from the difference in wastewater characteristics entering each WWTP. The above hypothesis was confirmed by other scientists, who showed that dewatered sludge from WWTPs located in the non-industrial catchment area (Warmia and Mazury, northern Poland) were characterized by a lower content of heavy metals, compared to those presented in this study, namely, Cd (1.1–1.9 mg·kg −1 ); Cu (132.4–242.6 mg·kg −1 ); Ni (9.8–91.5 mg·kg −1 ); Pb (8.0–17.9 mg·kg −1 ) and Zn (564.2–994.5 mg·kg −1 ) [ 14 ]. Moreover, the conducted research showed that according to Polish regulations, the content of Zn in the sewage sludge (S2) from WWTP4 exceeded the permissible concentration value for this element—in case of use of sludge in agriculture [ 8 ].…”

“…For these reasons, it has been successfully used in Poland and all over the world [ 9 , 11 ]. Moreover, sewage sludge contains organic matter and other substances needed by plants for growth, e.g., nitrogen, phosphorus, potassium, calcium and magnesium [ 1 , 11 , 12 , 13 , 14 , 15 ], and thus it is successfully used in agriculture as fertilizer or a regenerator for soil [ 11 , 16 ]. Unfortunately, as being the final waste material of wastewater treatment, sewage sludge also contains pathogens, poorly biodegradable organic compounds as well as heavy metals (including those toxic), etc.…”

“…It is commonly known that knowledge of the total concentrations of heavy metals in sewage sludge allows only for an evaluation of their pollution degree, but is not conclusive, with potential ecological risk that these elements may pose to the environment and living organisms, including humans [ 2 ]. This is due to the fact that the mobility, bioavailability and toxicity of these elements depend on their speciation forms, which are influenced by their leaching and interactions with different components of the natural environment [ 1 , 2 , 14 , 22 , 23 ]. One of the most popular methods for determination of the chemical forms of heavy metals in environmental samples (sediments, soils and sewage sludge), is the three-step chemical sequential extraction procedure, proposed by the Community Bureau of Reference (BCR), now the Standards, Measurements and Testing Programme [ 24 , 25 ].…”

“…So far, there have been only a few studies regarding the identification of the chemical forms of heavy metals in sewage sludge at different stages of its processing [ 2 , 4 , 35 ]. Unfortunately, the overwhelming majority of current studies concerns only the dewatered sewage sludge [ 14 , 16 , 17 , 31 ]. Therefore, in the present research, two types of sewage sludge were examined, i.e., thickened and dewatered and/or hygienized, collected at the beginning and final stage of the processing line, respectively.…”

The Use of Microwave and K* Algorithm in Determination of Alcohol Concentration in Liquids

“…Classification and clustering techniques are commonly used in environmental applications. Total heavy metal concentrations of sewage sludge obtained from mechanical-biological wastewater treatment plants were characterized by hierarchical cluster analysis [ 19 ]. Also, cluster analysis was used to investigate elemental concentrations of river sediments [ 20 ].…”