Can I dispose of a metol based dev down the sink?

MattKing said:

In many cases, the problems do come from quantity and the level of dilution.

A good illustration of this is someone who has run into problems because they've increased greatly the input to a septic system that has done its job well for years with lower, more typical quantities and varieties of household waste.
The same applies to municipal sewer systems.

A reasonably robust waste management system is capable of handling certain amounts of dilute chemicals without harm. Higher quantities may overwhelm that.

Many things are safe if quantities are low and dilutions are high, but dangerous if quantities and concentrations are high.

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That's all true and not in dispute. What I was saying was silly was the idea that Kodak et al were concerned with providing safe amounts for dumping down the drain. They were concerned with providing round amounts that seemed sensible for particular uses. 1 litre packs for a home user, 1 gallon packs for schools, barrels for major processing labs. It was (and still is) up to the user to deal with disposal.

Ilford have specifically mentioned on their website and in social media that their B&W chemicals sold to the public are safe to pour down the drain after use.

So yes. they do think about it.

Xícara said:

I've asked a neighbour that's an environmental scientist. He's going to ask some colleagues for me about agencies and regulations. Hopefully I'll encounter a "least bad" option for disposing of it. When I asked the silver extraction fellow what to do, he said to tip it down the sink with lots of water. So, that's probably what he does anyway after the extraction.... If I can find a better solution, I'll do it.

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I wish the solution to pollution was dilution.

Waste-water treatment systems are not normally designed to remove compounds that are not bio-degradable. The problems come when large enough amounts of such compounds go through the waste-water system and are then discharged back into the environment, i.e., into streams or lakes. Some photo chemicals degrade or are changed to benign stable compounds during waste-water treatment, some aren't. Still, even those that aren't may not pose a problem if the overall amount is insignificantly small, which is likely the case with lots of photochemicals.

Trying to keep toxic substances out of the environment is laudable. Doing a bit of research about the chemicals one uses and the local regulations regarding dumping the chemicals that one does use should enable one to make an informed and responsible decision.

Now if we could only find a way to deal with the PFAS, microplastics, prescription and non-prescription drugs and other things that find their way into the environment by way of the water-treatment facilities, we'd be making real progress.

I worked with the Austrian water and sanitation oversight board for years. There were problems with such things as mutated and hermaphroditic fish caused by hormones from birth-control pills making it into the environment through the sewer system among others. There are a lot bigger problems than those caused by photo chemicals.

Best,

Doremus

Xícara said:

Hi, I dispose of all my chemicals, ie. developers and fixers, responsibly with a fellow that services the local laboratories and extracts the silver. My usual roll film developer is PMK and I will continue to dispose of it in this way together with spent fixers. However I'm starting to use larger volumes of D76H developer to process sheet film and I'd like to know if this developer is safe, environmentally, to dispose of down the household sink. I guess not, but thought it might be worth asking here. Each litre of D76H concentrate has the following chemical amounts: 2.5g metol, 100g sodium sulphite and 2g of Borax. I'm using working solutions of 1:1 to 1:4.
Cheers,

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The amount discharged from a home darkroom is tiny and of no significance.