Used solution contains high levels of Copper and as John Gardner
    pointed out earlier Copper is highly toxic to a lot of marine (and
    freshwater) life.
            :
    I believe you will find that Copper Salts are present in a lot of
    plant control products (or [was] before being banned). Copper salts
    are also used to treat wood to prevent bacterial decay. I don't think
    that the sewerage works would thank you for killing off their bacteria.

My point is that copper (because of its widespread deployment) is almost
certainly something that the sewage treatment system has been designed to
cope with, and that the added copper from "a few PCB boards" is unlikely
to make any difference whatsoever...

BillW

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