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University of Technology and Life Sciences in Bydgoszcz, Kaliskiego 7, 85-796 Bydgoszcz, Poland
Publish date: 2017-09-01
J. Ecol. Eng. 2017; 18(5):118–124
Sewage sludge originated from wastewater treatment plants (WWTP) serving rural areas are suggested for agricultural or natural usage. Before, however, sewage sludge is subjected to the several pre-treatments, which involve stabilization, hygienisation and pre-composting. These methods decrease mainly the amount of organic substances and presence of microorganisms, but hardly affects concentrations of heavy metals. The advantages of using sludges as fertilizer for improving and sustaining soil fertility and crop production are many. The addition of sewage sludge to soils could affect potential availability of heavy metals. Trace elements are distributed in the soil in various forms: solid phases, free ions in soil solution, soluble organic-mineral complexes, or adsorbed on colloidal particles. In the study the concentrations of trace elements (Pb, Cd, Cr, Hg, Ni, Zn, Al, As, Se, B, Ba, Br, Ca, Cu, Fe, Mn, Na, Ga, Li, Mo, Sr, Mg, K, Ru, Tl, V, U) was tested in sewage sludge obtained from (WWTP) serving rural areas (PE< 9 000). In each case, the tested sewage sludge was meeting the criteria of stabilization and was used for agriculture and land reclamation purpose. All the samples were collected in 2016 and were subjected to microwave mineralization in a closed system in aqua regia. The total amound of macro and microelements were determined with a ICP-OES. It was found that the total concentrations of trace metals in all of sewage sludge are the same than Polish regulation limit of pollutants for sludge to be used in agriculture. The trace elements (cadmium: 1,16 mg·kg-1/d.m. in polish sewage sludge, respectively, much higher than those in the other countries. As a most prevalent copper and zinc were observed (111,28 mg·kg-1/d.m. and 282,94 mg·kg-1/d.m.). The concentrations of copper in polish sewage sludge are much lower (49-130 mg·kg-1/d.m.) than european sewage sludge (522-562 mg·kg-1/d.m.). The two out of tested heavy metals (beryllium, bismuth) were under detection limit, while gallium, molybdenum, thallium, vanadium and silver were detected in concentrations lower than 0,005 mg·kg-1/d.m. According to the obtained results, in all tested samples (the total amount of trace elements) did not exceed the limit values in sewage sludge for their use in agriculture and land reclamation.
Julita Karolina Milik   
University of Technology and Life Sciences in Bydgoszcz, Kaliskiego 7, 85-796 Bydgoszcz, Poland