Studies on the cytotoxicity of filtrates obtained from sewage sludge from the municipal wastewater treatment plant

Abstract

Possible reuse of the municipal sewage sludge (SS) in the agricultural area is connected with the necessity of monitoring this type of material in order to avoid an environmental risk. SS consists of a mixture of potentially toxic compounds, which may influence metabolism of human and other living organisms. For the estimation of the risk that SS may cause in an exposed organism, a variety of strategies are being implemented. They are based mainly on chemical analyzes, which cannot predict their toxicological impact, therefore, biological assays are crucial in such studies. The aim of this study was to present the influence of three types of SS filtrates: SS1 – sludge from primary clar-ifier, SS2 – sludge from aeration tank and SS3 – sludge from thickened sludge tank after flocculant addition. SS cytotoxicity was studied using Enterobacter aerogenes and Proteus mirabilis as experimen-tal models. The human cell culture model used in the study was represented by melanoma cells and fibroblasts. Statistically significant effect on bacterial cells exhibited SS2 and on cancerous cells – SS1. Taking into account above mentioned results, we conclude that the reuse of SS should be conducted cautiously and it is important for the SS to undergo a specific remediation process before introducing them into the environment.