Raw and biologically treated paper mill wastewater effluents and the recipient surface waters: Cytotoxic and genotoxic activity and the presence of endocrine disrupting compounds

Abstract

Paper mill effluents are complex mixtures containing different toxic compounds including endocrine-disrupting (EDCs) and genotoxic compounds. In the present study non-concentrated raw and biologically treated wastewaters from two paper mill plants with different paper production technologies i) Paper mill A uses virgin fibres, and ii) Paper mill B uses recycled fibres for paper production and the corresponding receiving surface waters, were assessed for their cytotoxic/genotoxic activity with SOS/umuC, Ames MPF 98/100 Aqua, and comet assay with human hepatoma HepG2 cells. In addition the levels of seven selected EDCs were quantified in wastewater samples and receiving surface waters. All investigated EDCs were confirmed in raw and biologically treated effluents from both paper mills with concentrations being markedly higher in Paper mill B effluents. In the receiving surface waters three of the studied EDCs were determined downstream of both paper mills effluent discharge. The wastewater samples and the recipient surface water samples from Paper mill A were not mutagenic for bacteria and did not induce DNA damage in HepG2 cells. On the contrary, half of the raw wastewater samples from Paper mill B were mutagenic whereas biologically treated wastewater and the recipient surface water samples were negative. In HepG2 cells most of the raw and biologically treated wastewater samples from Paper mill B as well as surface water samples collected downstream of Paper mill B effluent discharge induced DNA damage. The results confirmed that genotoxic contaminants were present only in wastewaters from Paper mill B that uses recycled fibres for paper production, and that the combined aerobic and anaerobic wastewater treatment procedure efficiently reduced contaminants that are bacterial mutagens, but not those that induce DNA damage in HepG2 cells. This study highlights that in addition to chemical analyses bioassays are needed for a comprehensive toxicological evaluation of complex wastewater samples.