Heavy metals in sewage sludge can be classified as difficult solid waste with potential hazards for environment. This report examined how an aqueous solution of EDTA (ethylenediaminetetraacetic acid) washing changes selected heavy metals’ (Zn, Cu, Cd, Ni, Pb) fractionation in sewage sludge. The analyzed sludge was dried and homogenized sewage sludge was obtained from a municipal treatment plant. The samples of sewage sludge were extracted with 0.1 M EDTA solution for 24 h. Primary as well as extracted sewage sludge was examined for the total content of heavy metals and speciation of mentioned heavy metals using BCR sequential extraction procedure. Analyzed sewage sludge samples were quite significantly contaminated with heavy metals. The total content of zinc, copper, cadmium, nickel, and lead in initial sewage sludge was equal to: 2306.5, 263.7, 9.0, 118.0, and 117.0 mg kg⁻¹ dM, respectively. After EDTA extraction: 1514.5, 253.5, 7.5, 83.0, and 58.0 mg kg⁻¹ dM, respectively. In sewage sludge before extraction, the percentage of metals in fractions I (exchangeable and carbonates), II (Fe and Mn oxides), III (organic matter and sulfides), and IV (residual) was: for Zn 21, 47, 31, 1%, for Cu 0, 0, 99, 1%, Cd 0, 32, 68,0%, Ni 28, 22, 42, 8%, and Pb 6, 3, 34, 57%, respectively. In sludge after extraction, the percentage of metals in fractions was for Zn 17, 47, 33, 2%, Cu 0, 0, 98, 2%, Cd 0, 30, 70, 0%, Ni 13, 20, 46, 21%, and Pb 4, 5, 24, 67%, respectively. EDTA washing resulted in decreasing of nickel and lead percentage in mobile fractions and an increase in fractions strongly bounded to sludge matrix. The effect was most evident for Ni. Efficiency of EDTA solution for zinc, copper, and cadmium fractionation changes was practically negligible. EDTA extraction influenced the content of metals in municipal sewage sludge fractions. The process caused a decrease in each fraction; however, a strong chelating agent removed metals mostly from a dominant fraction.

Organic matter present in natural water is a serious problem during water treatment in terms of the possibility of creating disinfection by-products (DBP). The new materials and processes are still analyzed in order to improve the efficient removal of organic matter as well as other pollutants from water intended for human consumption. The aim of the presented study was to evaluate the efficiency of using various combined processes: (a) coagulation and adsorption, (b) oxidation with ozone and coagulation, (c) oxidation with ozone, coagulation and adsorption, and (d) oxidation with ozone, UV irradiation, coagulation and adsorption for treatment of the modified surface water. In the presented study, the changes in pH, turbidity, color, organic matter content (evaluated as oxidizability, total and dissolved organic carbon content, UV 254 and 272 absorbances), and Ni²⁺, Cd^2+, and Pb²⁺ ions content were determined during modified surface water purification. Supporting the coagulation process by adsorption with additional ozonation and UV irradiation of the water sample improved the treatment processes of modified surface water. Processes associated with coagulation increased the efficiency of removing color by 4–16% and reduced the value of UV₂₅₄ and UV₂₇₂ absorbance by 10–20%. Using ozonation did not significantly change the content of total organic matter. Heavy metal ions were mostly removed by coagulation and adsorption processes (40–60%). Including ozone, oxidation resulted in insignificant changes in the concentration of metal ions in the purified water (less than 5%). During the treatment of the tested, modified surface water, the best efficiency was observed after the use of coagulation and adsorption processes enhanced with ozone oxidation. The additional involvement of UV irradiation did not have a significant effect on the removal of the analyzed pollutants.