My bar-napkin calculation shows .5 lb in 20,000,000 gal to be about 3 ppb by weight. The drinking water standard for copper is about 3000 ppb or so, depending on where you live. My reason for bringing this topic up in the first place is that Cu++ or CuSO4 is a potent bactericide. If you hit your 500-1000 gal septic tank with a big load of spent etch, you run a strong possibility of disrupting the beneficial bacteria that make your system work, with the attendant unpleasantness and expense of digging up your yard and wading around in a lot of "fecal refuse" to fix it. On a more global level, we have for way too many years just dumped stuff down the drain or put it in the trash and expected that it would simply disappear. Lead, Polychlorinated Bi-phenols, and Mercury come to mind as stuff that we didn't worry too much about until the birth defects and retardation were traced to them. Heavy metals in solution do undeniably unpleasant things to the environment, as anyone who lives downstream of a mine or a plating shop can attest. So, why not deal with the waste in a responsible manner and not just flush it or pitch it? Ed (the Tree-Hugger) Gisske ----- Original Message ----- From: "Liam O'Hagan" To: Sent: Monday, March 01, 2004 6:28 PM Subject: Re: ] My first PCB production > What is "contamination" though, 1ppm? 20ppm? > > I think it would go a lot further if you considered "contaminated" to be 1 > atom per gallon, than if you considered contaminated to be 1 gram per litre > for example > > > -----Original Message----- > > From: Jim Franklin [SMTP:jim.franklin@BTCONNECT.COM] > > Sent: Tuesday, March 02, 2004 11:20 AM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: ] My first PCB production > > > > I followed that link, > > > > "..Two pounds of root killer contain 0.5 pound of pure elemental copper > > enough to contaminate 20 million gallons of water..." > > > > It makes you think, doesn't it when you see those kinds of numbers... > > > > Jim > > > > ----------------------------- > > > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of William Chops Westfield > > Sent: 01 March 2004 23:15 > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: ] My first PCB production > > > > > > On Monday, Mar 1, 2004, at 13:54 US/Pacific, Spehro Pefhany wrote: > > > > > > > > But my wife, who is an expert in wastewater and other environmental > > > technical and legal matters, thinks a bit down the home drain with lots > > > of water isn't a technical problem. > > > > > > > > Note that in the US, it is relatively common (or WAS relatively > > common, anyway) to dump a couple pounds of copper sulfate down > > your toilet to kill roots that might have been invading your > > underground pipes. Or something. (Not that everyone is happy > > with this: http://www.city.palo-alto.ca.us/cleanbay/pdf/root.pdf ) > > > > Copper sulfate is also pretty widely used as an agricultural > > fungicide. > > > > If you get up to several ounces of copper per year (at 1oz per > > square foot of typical PCB, so, serveral square feet of finished > > PCBs), you should probably start thinking about being nicer than just > > flushing your used etchant down the drain. But that's a awful LOT > > of PCBs for the average hobbyist... > > > > BillW > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads