Re: I have a question
From: Judy Seigel <jseigel@panix.com> Subject: Re: I have a question Date: Fri, 19 Oct 2007 21:26:54 -0400 (EDT) > I admit it never occurred to me that it shouldn't be simply > discarded down the drain, and I wonder if it's OK because it > DOES break down so quickly? There are multiple points in discussion of these matters, and they should be kept separate. One problem is the regulation. Whether you can dump something down the drain, and in what quantity and other limitations (pH, maximum concentration, etc.) varies a lot depending at the city/town level in the US. I must say quite a few of the regulations do not make sense (especially in areas with fairly modern sewer treatment facility) but I do not advocate to violate them. Dumping formaldehyde, glyoxal, glutaraldehyde, etc. will most likely violate unless the waste is pre-treated to break the compounds. Another issue is the impact to the environment and/or the load to the treatment facility. For example, draining canola oil down the drain may not be technically banned in many areas, I would strongly advise not to do that, but rather to get a bag filled with old newspaper and dump the oil in it and throw it away as trash. Fat drained to the sewer system will require a lot of water to treat it and the load to the treatment facility is very high. Same principle applies to some of darkroom chemicals. Another issue is safety to the operator. Whenever possible I prefer not to keep waste chemical collection vessel in my darkroom because it would take many months to fill it up (due to my very small volume of hazardous chemical use), and accidental leakage, spill, etc. would be a bigger hazard to myself. I'd rather spend same effort to use safer alternative compounds. When small amount of waste is generated, whenever possible, I would rather treat/neutralize/oxidize the waste to inert forms before I accumulate them. > On the other hand, with chemicals I know are bad, I get them > concentrated (as for instance using a "first tray" for gum > development until it's practically as thick as molasses, > then putting it in the back yard with a screen over it until > it dries, & disposing of it as solid waste), I don't think it's a good idea to discard dichromate as solid waste. > tho on the 3rd or maybe it's 4th hand, someone (Mike Ware?) > said dichromate that's been oxidized and washed (or like > that) is a tri, not a di, and not bad. (I may have the > terms wrong, but I do recall the principle .) Perhaps you mean that dichromate (hexavalent form), once reduced to trivalent form, becomes less harmful to the environment. Like I said previously, one easy way to do this is to mix dichromate with gum or whatever, and let it get fully reacted. After this, sulfite can be added to make sure the conversion is complete. However, regulation of chromium in sewer water is a different matter and you should contact your local government body. For most small scale users, the best way to dispose these chemicals is to accumulate them individually (whether with or without pre-treatment), label each vessel clearly, and bring them to local household hazardous waste collection. For most standard b&w silver gelatin processing, waste chemicals other than used fixer, ferricyanide bleach and selenium toner can go down the drain to the sewer system (not septic tank), in small quantity, although they still contain undesirable compounds. Ferricyanide is the worst chemical used in conventional b&w processing. Alternative compounds are available but no one (but me) seems to advocate phasing out ferricyanide. I don't know why. -- Ryuji Suzuki http://silvergrain.org
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