Different toxic mechanisms in kraft pulp mill effluent for two aquatic animals

Bleached kraft mill effluent (BKME) seems to contain at least two different toxic mechanisms or materials which affect aquatic animals. BKME stored under clean and quiescent conditions, lost much of its toxicity for salmon parr ( Salmo salar L.) in 1 week, and all in 2 weeks. By contrast, it lost little toxicity to lobster larvae ( Homarus americanus Milne-Edwards) in 2 weeks. Bio-oxidation of BKME for 1 week eliminated toxicity for salmon parr, but did not greatly change toxicity for lobster larvae. Biooxidation for 2 weeks reduced but did not eliminate toxicity to lobster larvae. A waste treatment process which reduces toxicity of BKME for one species may not protect other species.