The Comparison of Selected Types of Municipal Sewage Sludge Filtrates Toxicity in Different Biological Models: From Bacterial Strains to Mammalian Cells. Preliminary Study

Abstract

Sewage sludge (SS) is a complex mixture of potentially toxic compounds, which may affect the environment. Many methodologies are being implemented in order to assess the risk that SS may cause after the exposition, but usually they rely on chemical analyses that cannot predict their toxicological impact. Therefore, biological systems are essential in such studies. The aim of this study was to estimate the effect of 3 types of SS filtrates: sludge from primary clarifier, sludge from aeration tank and sludge from thickened sludge tank after flocculant addition. In order to thoroughly investigate SS cytotoxicity, we proposed different biological models: Aliivibrio fischeri, Escherichia coli, Candida albicans and LN-229 glioblastoma cell line. Obtained results indicate that SS3 was the most toxic against A. fisheri, but tests conducted with the use of E. coli and LN-229 human cell line showed the higher toxicity of SS1. Different toxicity of analyzed filtrates in different biological models could be explained by differences in applied model structure, metabolism and life requirements. Therefore, the reuse of SS should be conducted with caution, and it is important for the SS to undergo a specific remediation process before introducing them into the environment.