Acute toxicity of ammonia-base neutral sulfite pulp mill waste liquor to rainbow trout.

The acute toxicity to rainbow trout of untreated ammonia-base neutral sulfite pulp mill waste liquor was demonstrated in these experimants. A mean LC50 of 0.82% and 95% confidence interval of 0.08 - 1.56% was obtained in four static bioassays. Lignin, sulfur dioxide, and ammonia were implicated as toxic components. The latter two were probably the most toxic.