When I permitted the construction of my darkroom, local waste management here in Beaverton, Oregon, told me:
"don't worry about dumping Selenium toner down the drain in any quantities- it will immediately be locked into compounds with organics (no lack of the brown stuff) and poses no threats to the waste management system or effluents downstream." They were only worried about quantities of used color chemistry, including large amounts of silver compounds.
So unless you are in the Central Valley of California near Kesterson Refuge**, you're going to be ok ;-)
** Kesterson NWR is at the end of the drainage system for San Joaquin Valley, which naturally has high concentrations of Selenium in the soil. When the Central Valley was irrigated, the compounds leached out of the soil and ended up in high concentrations at the bottom end of the drain, along with lots of residual pesticides and fertilizers. Life basically sucks for the birds at the refuge. But the pesticides and fertilizers are what's killing them....
Whenever something like this gets going in a forum you get all kinds of crazy edicts, misinformation, and off the cuff comments. Most of it is out of context or wrong. Things that need to be kept in mind, but usually aren't are these:
What is toxic? In what form? At what exposure? What kind of toxicity? How can exposure occur? What does the substance in question bond to or break down in to? For instance in this case the depleted selenium mixture mostly isn't selenium. It's depleted. So what is it now? At what concentration or dilution? If it goes down the drain what will it do? What will it be or what form will occur if a plant or animal takes it up? Which plants or animals? Everything is toxic at some level or form of exposure including light and water. Pyrogallol for instance is pretty "toxic". It comes from acorns and other seed pods. Used as a developer, it rapidly oxidizes into something else. So when you dispose of it, you aren't disposing of Pyrogallol, or at least what's left won't be very soon, so what exactly are you dumping down the drain in real terms? What I'm trying to say is that there is more to it than just yelling "Poison!" or "Toxic heavy metal!" or as a counterpoint, dismissing safe and responsible practice.
What is the proper method of disposal? "Dispose of Properly" is a statement to limit liability, nothing more. It can mean anything from pouring it down the drain to taking it to a hazardous waste disposal facility. If you aren't sure, find out what is proper for a particular compound for your locality.
It's important to have an understanding of the things you are working with. It doesn't take a chemistry degree to understand, but it does take some effort. For instance, here we already had selenium described as a "toxic heavy metal". While photographic selenium solution requires handling procedure, and shouldn't be dried out and inhaled, etc. describing it that way is incorrect. It is a common ingredient in fertilizer, dandruff shampoos, and quite a few other things, and can even be taken as a supplement. Again, quantity, kind, and exposure. Toxic is a broad term. Context is key. How much ETDA is in two pounds of spinach, and do I need to be afraid?
Last edited by JBrunner; 01-29-2009 at 01:36 PM. Click to view previous post history.
Originally Posted by leicam5
I'm not a chemist, but my sister has a Masters degree in Biochemistry, and she wasn't concerned when I told her about my setup.
Originally Posted by Colin Corneau
I dump my used Selenium (less than one-half gallon) in a 5-gallon bucket, take it to the greenhouse and fill it up with water (so about a 10:1 dilution). And yes, I do use it on my vegetable garden, as a supplement to regular watering. The tomatoes seem to thrive on it.
As mentioned in other posts selenium can be beneficial, in the right quantities Selenium is an essential micronutrient, being a component of the active site of glutathione peroxidase (an antioxidant enxyme in animals), and has been shown to improve growth in plants.
Originally Posted by Colin Corneau
Yes, selenium toner needs to be treated with respect when made (if you do it from scratch) and used, but disposing of exhausted solutions to the drain, or pouring onto soil may actually be beneficial to the local environment. And if you grow your own tomatoes, beneficial to yourself.
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