Flotation as a remediation technique for heavily polluted dredged material. 1. A feasibility study

Wastewater sludges were analysed in the Allium cepa genotoxicity test. They were sampled during three winter periods from three Danish municipal wastewater treatment plants differing in size and industrial load. The toxicity of the sludge was tested in the Allium root inhibition assay, and the results expressed as EC30 and EC50 values showed that the toxicity could be positive correlated to the industrial load. However, when genotoxicity was tested at concentrations corresponding to the EC30 and EC50 values in the A. cepa anaphase-telophase assay, only two sludge samples from the smallest plant with the lowest industrial load induced significant chromosome aberrations. Concentrations of the heavy metal's Pb, Ni, Cr, Zn, Cu, and Cd were also determined and could partly be correlated with the toxicity of the sludge and the industrial load of the treatment plants.