Conference on Environmental Science and Technology

Society high pressure on the quality improvement of river and lake water pushing authorities to provide more and more sophisticated treatments to clean wastewater in municipal wastewater treatment plants. These activities helping the environment to minimize contaminant transport on one site, producing more sewage sludge (SS) on the other site. 27 EU states generate annually around 13.5 mil. tons of dry solids. Huge amount of SS is a great source of all nutrients, mainly strategic P and organic matter. Land applications can substantially decrease consumption of mineral fertilizers and protect natural resources. Direct land sewage sludge application is limited by the presence of inorganic and organic contaminants, which can directly affect growing plants and subsequently food chain. Origin and properties of inorganic and organic contaminants are completely different therefore one step treatment cannot be applied. We have tested two steps cleaning procedure to remove all contaminants from the sludge. The chelate extraction was applied on the release of toxic elements and pyrolysis on the removal of organic contaminants and decay of any microplastics. Results of applied treatments showed that chelate extraction substantially decrease bioaccessibility of metal content, and their uptake by spinach biomass. Pyrolysis at 550o C did not substantially affect metal ability and their accumulation in plants. Pyrolysis removed persistent organic contaminants from sludge, therefore the risk of their plant uptake is diminished. Combined treatment showed promising results related to safe sludge field application.