----- Original Message -----
From: "Scott Loveless"
Subject: Re: Used fixer?
Free silver is significantly different than a silver thiosulfates,
which is what you get with photo fixer. Unfortunately the
Environmental Political Association doesn't make that distinction very
well. Probably most of the silver in used fixer manages to bind
itself to the sewer pipe sludge before it even hits the waste water
plant. (That's right, it sticks to the crap, literally, in your sewer
lines.) The rest of it, once diluted with your own waste water and
everyone else's sewage is so insignificant that it really doesn't
matter. What little of it that makes it into the the water downstream
from the plant most likely ends up in the silt on the bottom of the
stream. The absolute worst case scenario is that it causes a moral
panic and the EPA over-regulates some industry again.
Kodak ran a series of tests in the 1970s and 80s to determine what the
environmental impact of silver thiosufate actually was. Admittedly one could
say that they have a bias and a vested interest, but then, one could say the
same thing about the EPA.
Kodak was selling silver recovery equipment at the time, so they stood to
gain from silver effluent regulations, so it's hard to say where their bias
would have been, if they even had one.
Anyway, they determined that silver thiosulfate is an environmentally inert
compound, with the silver so tightly tied to the sulphur that the compound
is effectively non reactive.
Common sense would lead one to believe that if your local recycler will pick
up and dispose of your small amount of used fixer and actually treat it and
crack the silver out, then it is a good thing to do, but depending on the
recovery method, there may be more harm in recovery than there is in letting
it go into the waste stream untreated.
There is an environmental impact with the recovery process.
It takes close to 40 amps of electricity to crack out the silver
electroliticaly, power which has to be generated by a power plant somewhere,
or the sacrificial metal method of recovery involves manufacturing of iron
wool, which also has an environmental impact, as the stuff has to be mined,
refined and then made into an acceptable product.
All of the recovery methods are environmentally harmful themselves at some
or many levels.
The responsible thing to do is to look at how much real harm there is in
dumping low levels of what may well be a harmless silver salt down the drain
compared to the very real environmental damage caused by recovering the
silver from the salt compound and making an educated decision based on
lowest risk.
The irresponsible thing to do is to do more harm than good by blindly
jerking ones knee into an environmental goose step.
William Robb
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