QUANTIFICATION OF TOTAL AND METAL TOXICITY IN WASTE-WATER USING ALGALBIOASSAYS

Based on the fact that EDTA complexes free metal ions, a method combin ing algal assays, electron microscopy and EDX-ray microanalysis was de veloped to determine total and metal toxicity in full strength effluen t water. By adding a sufficient amount of EDTA into a test water to bi nd the free metal ions, metal and 'organic' toxicities could be differ entiated in assays, as observed from tests with two industrial wastewa ters and a solution containing a mixture of Cu, Zn and Hyamine. Metal toxicity could be verified by the presence of free metal ions in the w ater and by excess metals in the polyphosphate bodies of affected alga l cells where altered chloroplasts were observed, Damage to the thylak oidal membranes in the chloroplast was characteristic of metal toxicit y in Chlorella cells.