ECOTOXICOLOGICAL ASSESSMENT OF THE SOILFERTILIZED WITH SEWAGE SLUDGE

Abstract

Sewage sludge and its management constitute one of the most important environmental problems. The introduced the Sewage Sludge Directive 86/278/EEC advocate utilization of sewage sludge in agriculture. However, this method is limited mainly by the availability of heavy metals and pathogens. An ecotoxicological assessment of sewage sludge doses applied to soil, recommended in the Polish Regulation of the Minister of Environment of 6th February 2015 on municipial sewage sludge, was carried out. The sewage sludge was added to soil in the amounts of 3, 6, 9, and 15 Mg/ha. The produced mixtures were subjected to physicochemical and ecotoxicological tests, involving the biomass and mortality tests of Eisenia fetida earthworms. The sewage sludge had a statistically significant impact on the increase in: electrical conductivity, total exchangeable cations, organic matter content, organic carbon, nitrogen and heavy metals of the considered soil. The impact on the biomass of earthworms was different; after 7 days in the mixtures with 3 Mg/ha and 6 Mg/ha sewage sludge addition, the biomass increased approximately by 1.3-fold, in comparison to non-modified soil. At 9 Mg/ha, it reduced by 1.3-fold, whereas at 15 Mg/ha – by 16-fold, in relation to the initial value. The studies indicated that the ecotoxicological assessment of wastes may be employed as environmental safety control measure of the sewage sludge application in agriculture.