Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Perhaps someone with some knowledge on public works and sewage treatment can
clarify this for me.

I guess it must be the copper in the ferric chloride etchant that we dispose
of that is the problem - is that correct? Is there actually copper per se
any more after the reaction of etching?

I'm pretty sure somewhere in the sewage treatment process, after gross
solids are removed, the water in the sewage system is sent to settling
ponds. While in the ponds ferric chloride is added to act as a flocculent
i.e. an agent that causes solids to gather together in clumps for easy
removal. If this is the case, would it make any difference if there were
some ferric chloride in the system to begin with (from flushing etchant down
the drain)?



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