Re: CO2 BLEACHING AND DIOXINS

[Philip Fleischer <philip@coc.powell-river.bc.ca>]

Do you mean ClO2?

I have not seen or read much on this.  Use of chlorine dioxide rather than
chlorine probably reduces the amount of dioxins in effluent as I have heard
people claim.

But, dioxins are still produced.  They come out the stacks of power
boilers and recovery boilers, vapourize out of the wet end of the pulping
process, and they are still in the product.

Along with the switch to ClO2, pulp mills have changed their process other
ways and it is not easy to tell what is really going on.  Some have added
secondary processing and burning the sludge can put more metals and more
of other chlorine species like PAHs in their airborne effluent.  Ocean
sediments around many mills are still loaded with dioxin.  Measurments
of dioxin in fish tissues can generally be presented as decreasing.  However,
they use the tricks of claiming decrease when the 2,3,7,8TCDD congener is
down but TEQ is up, or, they go the other way when convenient.  They have
learned where and how to sample to get better results. (Quality control)

Chlorine dioxide introduces several new problems.  It is a very dangerous
chemical.  There was a very big spill of it here less than a year ago,
the socio-political fallout of which is still being processed.

Chlorine dioxide results in Chlorate (ClO3-) in the ocean from coastal mills.
I have one ref on this, a paper in Ambio 17(6):1988 by Karl-Johan
Lehtinen and two other Scandinavians which deals with the Chlorate problem
in the Baltic.  One of the consequences discussed is damage to the
herring fishery.




Philip Fleischer    Philip@coc.Powell-River.BC.CA    604/483-4701