Can I just throw my chemicals down the sink?

A friend of mine monitors sewers for a living and knows a thing or two about what should and shouldn't go down them. I once asked him about putting fix down the sewer.

His response was that from a home darkroom it wasn't going to be a problem. He said that silver would get precipitated out at the treatment plant and the quantities were so small compared to many other chemicals in sewers it really wasn't worth worrying about.

Larger quantities are a different matter.

Sorry for digging up a slightly aged thread... Just my 2p.

I contacted Scottish Water (those who take care of our water supply here) a while back with this very question. I was directed to their industrial pollutants people, and a nice lady there told me that dev and stop were nothing to worry about. She then looked up my address in her database to check where our waste got processed, and discovered it was a huge plant across town. On the basis of that she told me that the quantities of fix I had to dispose of wouldn't make any difference at all.

She instructed me to put everything down the 'dirty' waste pipe as she called it - which meant kitchen sink or toilet - and make sure it was plenty diluted, but otherwise not to worry.

All this was on the undertstanding that I was a home amateur producing relatively low volumes of waste (all in, a couple of litres a month), and it was a different story for a high-output lab. She sent me a copy of their guidelines for labs, for my information.

To be honest, she seemed quite pleased, if rather taken aback, that I was concerned enough to contact them for guidance.

Considering the millions and millions gallons of wast water that is processed in the metro Phoenix area the quart or two that I dump down the sink is nothing to lose sleep over. On the other hand even a minlab needs to me monitored.

goodyear said:

On the basis of that she told me that the quantities of
fix I had to dispose of wouldn't make any difference at all.

She instructed me to put everything down the ... kitchen
sink ... and make sure it was plenty diluted, but otherwise
not to worry.

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Welcome reassurance from across the ocean!

Plenty diluted is the way I use developer and fixer. I don't
bother with a stop of any sort. One shot usage precludes
the build up of silver or other deleterious substances. Dan

dancqu said:

One shot usage precludes
the build up of silver or other deleterious substances. Dan

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You are producing the same amount of silver etc, but distribting it in small and dilute doses, which is fine.

Any silver in fixer will very quickly become silver sulphide in a sewer. Silver sulphide is very insoluble and very unavailable to life forms. Sodium thiosulphate is used in water purification, so maybe it's not so bad.

I'm not so sure, though, about developing agents with benzene rings (hydroquinone, pyrocatechol, pyrogallol).

john_s said:

I'm not so sure, though, about developing agents with benzene rings (hydroquinone, pyrocatechol, pyrogallol).

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The phenols we use in developing aren't a proper benzene ring, first -- benzene has three double bonds distributed along all six of the carbon-carbon bonds; the phenols we use have single bonds all around the ring AFAIK. And those phenols (metol, HQ, catechols, pyrogallol, p-aminophenol, etc.) all oxidize very quickly once the developed is diluted out to the point where there isn't a significant presence of preservative (like sodium sulfite) present. By the time they reach a treatment plant or spend any time in a septic tank, developing agents have turned into tannins or similar staining/tanning agents.