Third Law of Thermodynamics - entropy - there's no free lunch! Regards, Bob S.
On Sun, Mar 15, 2009 at 3:08 PM, William Robb <[email protected]> wrote: > > ----- 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 > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
