APPLICATION OF NEW MARINE BIOASSAYS FOR ASSESSING TOXICITY OF BLEACHED EUCALYPT KRAFT MILL EFFLUENTS

A suite of standard bioassays using sensitive local species of marine phytoplankton, macroalgae and fish larvae was developed and used to de termine the toxicity of laboratory produced bleached eucalypt kraft mi ll effluent. The treatment effluent was not toxic to any of the four s pecies tested. The untreated effluent, however; was toxic to both the marine phytoplankton and the bacterium, with EC(50) values oi 11% and 72% respectively (the lower the EC(50) the more toxic the effluent). A pproximately 40% oi the toxicity to the microalga Nitzschia was associ ated with the high molecular mass fraction. Based on limited data, tox icity was correlated with total organic carbon and BOD in the effluent s, but was not correlated with AOX, COD, chlorate or 2-chlorosyringald ehyde concentrations in the effluents. 2-Chlorosyringaldehyde was much less toxic than the more highly substituted chlorophenols found in ef fluents produced from softwood pulping and elemental chlorine bleachin g. Of all the bioassays, the algal growth inhibition test was the most sensitive and the most reproducible, but required a three day exposur e to the effluent. The seaweed fertilization test, though less sensiti ve, was extremely rapid. The blenny larvae test was less robust and so me problems were encountered with availability of larvae throughout th e winter months.