I've had the luck to enjoy a career in scientific research and analytical chemistry before taking up photography full time. One of my challenges was teaching chemists at the local water supply and sewerage department about photographic chemicals in the effluent they had to treat. Of course I had an agenda. I wanted building approval for a house with sizeable darkroom in it. They did said yes to my plans.
The following does not apply to industrial scale photo materials manufacturing or a major processing lab, only households connected to a sewer line or a proper septic system:
Developers are mild reducing agents that oxidise rapidly to inert components. The BOD (Biological Oxygen Demand) challenge offered by a darkroom is much smaller than the BOD from a dishwasher, in-sink garbage disposal unit, or a toilet.
Stop bath is a very mild acid that has no measurable effects on highly buffered systems like septic tanks or sewerage treatment plants.
In moderate quantities (pounds, not tons) silver tetrathionate and similar compounds which characterise used fixer don't harm sewerage treatment systems. The silver very quickly gets converted to silver sulphide in the presence of the free sulphide ion (smells like rotten eggs!). Silver sulphide is geologically stable and inert and has one of the lowest solubility products known in chemistry. The stability and inertness of silver sulphide is the key to the remarkable archival properties of sepia toned photographs.
Before my darkroom was approved by my local council I had to calculate the silver concentration in my total household effluent. I'm pretty busy and use a few thousand sheets of film and paper per year but the result came to about 5 parts per billion. By the time this mixes with the output of the other 20 000 households in my area that don't process photographic materials the silver concentration is below any conceivable detection limit down at the sewerage treatment plant.
You can do your own calculations. Just calculate your yearly use of silver from your photographic materials consumption and divide this by your yearly water consumption from the water meter.
The world being what it is many local effluent standards are written by lawyers and/or accountants who don't know a dot of chemistry but know about culpability and lawsuits. If you encounter such local regulations and you want to ask permission I guess you have to do what they say.
Thiosulfates and sulfites, the main constituents of fixers, are pretty innocuous. Pouring them down the drain is usually quite acceptable. But in a darkroom that does a lot of work, like a college darkroom, reclaiming the silver dissolved in spent fixer can be very significant. Such places almost always use some means of extracting the silver before discarding the other stuff, or they send their spent fixer to a contract reclamation firm for $.
Maris, stop being so bloody reasonable!:D
By the way...
Kodak Publication J-300 - "Environmental Guidelines for Amateur Photographers."
• Developers and wash agents may be discharged to municipal sewer systems in moderate quantities without fear of harm.
• Acid stop baths may be discharged if neutralized with sodium bicarbonate (baking soda) first.
• Fixers may be discharged AFTER silver has been removed.
• Exotics such as Selenium should NOT be discharged.
I take the extra step of turning in my spent fixer after desilvering but I don't neutralize stop bath so, according to Kodak's recommendation, I guess I'm about on par or a little above.
[Runs to the kitchen to find the baking soda.]
I took a workshop from a famous photographer and ardent environmentalist who told us that darkroom chemicals are chemically similar to chemical fertilizer, so collect them and spread them on your lawn. I asked about selenium being a poison and he refuted that as if there was no truth to it. I know that in our workshop a fair volume of stuff went right down the drain, presumably into the unconfined river floodplain aquifer (I'm a geologist by training).
So that's the word from a lefty tree hugger photog (the teacher, not me) who spends much of his time and money fighting land development in western Washington State.
But if one uses stop bath until the indicator turns purple, does not that mean it is already neutralized?
Originally Posted by Worker 11811
At home, I dump the fixer, usually 1-2 liter bottles, down the drain. My volumne as of recently had decreased a lot at home since I havent had much time at all.
At work, the fixer is collected in large marked containers that are taken out once they fill up by whatever hazmat/recovery people maintenance calls up.
At home, I mark off the number of rolls I fix per liter (max of 24, 36exp rolls in rapid fix) and test paper fixer with hypo check. At work I only use hypo check on fixer to text exhaustion.
I suppose that's true but isn't it a lot more fun to watch it fizz? ;)
Originally Posted by Vaughn
Seriously, I reuse stop bath for the duration of the session or if I think I'll be developing or printing soon but, otherwise, I dump it.
Neutralize stop bath?
Originally Posted by Worker 11811
Do you neutralize salad dressing before you pour it down the drain? Working strength stop bath is about as acidic as a 1+1 dilution of vinegar. In fact you can just use white vinegar 1+1 with water if you want, or run out of stop bath and have vinegar.
Thanks to this thread I don't feel guilty anymore when dumping the chemicals down the drain. But then again I didn't feel guilty in the first place.