But recovering that silver involves costs: collection, precipitation, transport, refining, and re-melting. At today's spot price that quantity of silver fetches about $50. Here's a typical calculation: if a home darkroom processes, say, 2000 sheets of 8x10 black and white photographic paper a year and suppose half the silver goes down the drain that's about 3 ounces. Even Kodak publication J-300 which is the de facto last word on "fixer down the drain" is more about avoiding potential industrial and environmental litigation and less about the niceties of ultra-small scale chemistry. 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 alarm, blame, culpability, and lawsuits. The extra water can also overwhelm the soakage pit or trench that lies at the end of the septic system and deliver a squelchy smelly mess underfoot. Sending maybe two or three hundred extra litres of water a day into a system not designed for it dilutes the activated sludge and slows the biological reactions that process and neutralise the usual septic stream. In every case it has been the fault of extravagant archival washing at the end of the processing sequence. In my professional career I have inspected home septic systems that have been "ruined" by people doing photographic processing. People washing silverware in their dishwashers will send down more silver than you will ever do. Down at the treatment plant your speck of silver won't be detectable by any known analytical technique. If you are discharging into a sewer system your used fixer contribution will be diluted by thousands of household that don't do photographic processing and that's just about everybody. I bet it's in the parts per billion range where no conceivable biological effect can be credibly imagined. Allow for 1 milligram of silver per square inch, and divide this by your yearly water consumption from the water meter. Just estimate your yearly use of silver from your photographic materials consumption. The stability and inertness of silver sulfide is the key to the remarkable archival properties of sepia toned photographs.ĭo your own numbers. Silver sulfide is geologically stable and biologically inert and has one of the lowest solubility products known in all of chemistry. The silver very quickly gets converted to silver sulfide in the presence of the free sulfide ion (smells like rotten eggs!). In moderate quantities (ounces, not tons) silver tetrathionate and similar compounds which characterise used fixer don't harm sewerage treatment systems or septic systems. Stop bath is a very mild acid that has no measurable effects on highly buffered systems like septic tanks or sewerage treatment plants. The BOD (Biological Oxygen Demand) challenge offered by a home darkroom is much (much!) smaller than the BOD from a dishwasher, in-sink garbage disposal unit, or a toilet. The following does not apply to industrial scale photo materials manufacturing or a major processing lab, only single households connected to a sewer line or a proper septic system:ĭevelopers are mild reducing agents that oxidise rapidly to inert components. The "no fixer down the drain" anxiety comes up about a hundred times a year and has been doing so for at least half a century. 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. I've had the luck to enjoy a career in scientific research and analytical chemistry before taking up photography full time. I post this one a few times a year but it is still relevant. As far as I know, that septic system is still doing just fine years later. The small amounts of ferricyanide bleach I used went into the septic system as well. Selenium toner gets replenished and reused I never dump mine anywhere. Fixer was collected and taken to a local photo lab for silver recovery (this is by far the best way to deal with fixer hazardous waste disposal sites actually mark it toxic and then incinerated it at high temperature. My end result was that I would dump both film and print developers and the stop baths (after mixing both together). Oxygen load on the septic system in a consideration and depends on the size of your system and the amount of chemistry you are disposing. I don't remember all of that now, but look for an older version of Kodak publication J-300. I did quite a bit of research at the time about what to dispose of (and how much) in the septic system and what not. I worked in a darkroom on a septic system for several years.
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