on the contrary. first of all, water isn't treated for "specific" pollutants other than those at high concentration, which is usually bacteria. to remove copper from drinking water would require either reverse osmosis (which will produce a more concentrated waste stream as well) or resin deionization, which is also expensive and not generally done at treatment plants, and in that case the copper comes back out when you regenerate the resins. copper is extremely toxic to fish larvae, it will completely kill them at low ppm or ppb levels! i worked for a water treatment company and got a call from a game and fish guy about it once, and i think it was ppb they were worried about (they ideally wanted to remove the copper but not the other minerals in the stream water at a hatchery, not really feasible). it all adds up.=20 pollutants from households are the major problem in areas without major manufacturing industries. =20 it certainly is very unlikely to be removed from sewage before it's dumped back into a river etc. sewage plants mostly remove the sand etc. (to make the rest of the process simpler), sterilize it, and then culture it with various bacteria to convert much of the organic matter into CO2 which is vented into the atmosphere, and then the "floaters" are skimmed off (i've been to our local sewage plant checking their fire extinguishers, i was very impressed, particularly as i hadn't realized that most of it is underground). the copper does not magically go away. in general, the more a waste product is diluted and mixed with other waste the harder it is to recover/remove. also, some materials become more toxic over time in the echo system rather than being broken down.=20 this is often true for metals as they are integrated into organic compounds in plants/animals and them accumulate in the animals towards the top of the food chain, hence mercury winding up in fish in some locat= ions. sodium hydroxide is not that dangerous, to any one with a clue on how to handle chemicals. i.e. gloves, goggles, and an apron if possible.=20 you'll note the household "lye" is sodium hydroxide (for etching you want the cheap stuff, not the stuff with metal pieces to make it self heat more and make it more active) and they don't even suggest goggles on those bottles (though they should). it's also easy to neutralize and precipitate the copper out of, so that the copper can be filtered out before disposal and accumulated in a small container waiting to be taken to your local recycler or household hazardous waste facility (which many cities have). honest, we don't need to add more trash to the water system, it all adds up. it is illegal in most places, and people ignoring this law are the main reason that processed sewage can't usually be used as fertilizer (i.e. too many metals that have been illegally dumped down the drain, often by commercial interest like electro-platers etc.). please, please try not to dump stuff down the drain that you shouldn't, most things aren't that hard to take care of. solutions that won't precipitate can still usually be reduced through evaporation outside (though not solvents as that just causes air pollution, because of it's low density it takes very little to pollute the air). the chemistry department at my high school recycled nearly all of their chemicals.=20 the instructor would take the end products of experiments, possibly refine them a bit, sometimes do another reaction on them, and then wind up with chemicals for the next years class without having to buy new chemicals or dispose of last years in most cases. there was a time when people dumped all kinds of things down the drain, there was also a time when shoe stores had x-ray machines in their stores to "measure" your' feet (they were mostly a gimmick). eventually the government realized that casual x-ray exposure for useless reasons wasn't so smart, and the machines disappeared, the same holds true for how chemicals have been dumped! immobilizing it in plaster of paris just makes it a problem for someone else farther down the road. eventually those land fills will be mined for metals etc., and they'll have to deal with this chunk of garbage weighing several pounds with only a little copper that has to be dealt with in some way. if you mail your' problems away, they will come back postage due, if not in your' lifetime then in someone else's, and you hardly have the right to mail your problems to others. also, FeCl also produces fumes, though not as bad as HCl. any etchant should be used with proper ventilation, goggles, and preferably a lab apron. nothing that dissolves copper is going to be friendly to human tissue, especially the eyes and respiratory tract (and lungs are really e= xpensive). William Chops Westfield wrote: >=20 > > > > Now... Sodium hydroxide looks like it should be easy enough to get - > > assuming > > I can find the stuff in the first place (and in fairly small > > quantities, i.e. > > 500g tubs). The problem is the pH paper... >=20 > You know, I find the thought of people messing around with lye in > attempts > to be politically correct about the disposal of hobbyist levels of spen= t > etchant to be deeply disturbing. Lye is seriously DANGEROUS stuff. > Copper > (as sulfate) is/was routinely dumped down drains in pound+ quantities t= o > control roots in drainpipes. Copper isn't great for the environment, > but > it's pretty much an expected pollutant for populated areas, and is > probably > removed in the course of normal water treatment. Adding the copper > from > a couple square feet of boards (at about 1oz/sw foot) isn't a big deal. > If > you're an industrial-scale PCB factory etching square meters per day, > then > other rules would apply. --------- --=20 Philip Stortz--"In Germany they came first for the Communists, and I didn't speak up because I wasn't a Communist.=20 Then they came for the Jews, and I didn't speak up because I wasn't a Jew.=20 Then they came for the trade unionists, and I didn't speak up because I wasn't a trade unionist.=20 Then they came for the Catholics, and I didn't speak up because I was a Protestant.=20 Then they came for me, and by that time no one was left to speak up." -- Martin Niem=F6ller, 1892-1984 (German Lutheran Pastor), on the Nazi Holocaust, Congressional Record 14th October 1968 p31636. _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist