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Biologically treated combined mill effluents sampled at nine bleached kraft mills were surveyed for chlorinated neutral organic compounds. The test results showed only four main chlorinated compounds: chloroform (7-105 Pg/L), , -dichlorodimethyl sulfone (64-429 pg/L), a,-, '-trichlorodimethyl sulfone (0.3-12.4 pg/L), and (tentatively) , , ', '-tetrachlorodimethyl sulfone (0.4-1.1 Pg/L). Unlike chloroform, the chlorinated sulfones were found to be relatively resistant to removal by biological treatment in an aerated lagoon. However, preliminary assessment of fish bioaccumulation potential, acute fish toxicity, and Ames mutagenicity indicated that the chlorinated sulfones would have no immediate adverse effect on the aquatic environment.

A "monomer-free" (i.e., predominantly high molecular weight chlorolignin) solution prepared from spent liquor collected from the alkali extraction stage of a softwood kraft pulp mill bleach plant was examined for its ability to release monomeric chlorinated phenolic compounds when stored under sterile conditions at pH 7. The major chlorinated phenolics released from the chlorolignin solution, after 28 days of storage at 50 °C, were 4,5-dichloroguaiacol, 3,4,5-trichloroguaiacol, 6-chlorovanillin, and 5,6-dichlorovanillin. These four compounds were found to reach maximum concentrations over the storage period, which corresponded to only 2.3-3.6% of their concentrations in the original E-stage effluent. The remaining chlorinated phenolics normally present in spent bleach liquors did not reach concentrations of >1 µg/L over the course of the experiment. A spiking experiment using 13C-labeled 4,5-dichloroguaiacol demonstrated that the chlorinated phenolics which are released from the chlorolignin over time may be the result of the slow desorption of chlorinated phenolics which had become associated with the chlorolignin during the bleaching process and not necessarily due to chlorolignin degradation as previously hypothesized.

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