Fixer and the Environment

Discussion in 'Black and White' started by kathryn_treacy, Aug 18, 2016.

  1. Hello,
    I am doing my science fair project on photography and I need to know why my teacher lets us dump the developer into the sink but wants us to put the fixer back in the bottle.
    Is there a specific reason for this? Does it harm the environment?
    Thank you!
  2. That’s a good question!
    There are two fixer chemicals, both do the same job. The original fixer is sodium thiosulfate which is customarily replaced by ammonium thiosulfate.

    Photo films and papers are coated with unflavored and highly purified gelatin. This is the binder (glue) used to affix the light sensitive material to the film or paper base. Gelatin is chosen because it is transparent, flexible, and preamble. The gelatin coat swells when wet, this allows the chemicals of the process to infuse and reach the light sensitive chemicals. When the material dries, is shrinks back to it original size.

    The light sensitive goodies are salts of silver. These resemble table salt, however they smaller crystals and slightly off white. When exposed to light, they are rendered developable. The developer is able to distinguish the differences between exposed and none-exposed crystals. The developer reduces (splits) the exposed silver salts into its two component parts. The silver part remains trapped in the gelatin. This is metallic silver and it is opaque. This is the metal that makes up the photographic image. The other component is a halogen. The liberated halogen is dissolved away by the developer which is mainly water. Halogen is Swedish for “salt maker”. We use thee members of the halogen family of elements in photography. These are bromine, chlorine and iodide.

    After the developer has done its job, an image is seen. This image is comprised of metallic silver. Surrounding the metallic silver image will be silver salt crystals that were not exposed and therefore did not develop. It is necessary that these be removed from the gelatin. If they were to remain, in time, they self-reduce and liberate metallic silver. This is also opaque and it blends in with the desired image. The result is, the entire image will darken. We say it faded.

    Fixer to the rescue: We immerse the film or paper in a fixer solution. This is a solvent for silver salts but not a solvent for silver. The unexposed and thus un-developed silver salts are washed away and dissolve into the fixer which is mainly water. The image comprised of silver remains. We than wash the film or paper to purge it of residual chemicals.

    How dangerous is the chemicals of the photo process? The answer is – they are pretty benign.
    Test after test has shown they can safely go in the sewer system. OK – what are the ramification? The spent fixer contains silver in solution. Some forms of silver are toxic. The authorities are afraid that the fixer will disrupt the biological action of the sewer treatment plant. This likely won’t happen because as the fixer travels in the sewer line, sulfur is comes out of solution. The sulfur and the silver combine to form silver sulfide and inert chemical. Why photo waste is considered toxic? Again some forms of silver are toxic and when a municipally tests photo effluent they use nitric acid to test. This liberates the silver and the outcome of the test is positive. The municipality must dispose of solids generated by the waste treatment plant. If it test positive for silver, its value as a fertilizer is reduced.

    Now the real harm: Fixer is the same chemical used in tropical fish hobbies. This is the chemical they add to purge city water of choline. The municipal sewer must treat discharged effluent with chlorine to render it safe from bacteria. If lots of fixer is in the sewer, they must use double or triple the amount of chlorine. This is costly.

    Is photo chemical effluent benign? The authorizes are not worried about this unless the source is a big industrial photo lab. Hobbies and school darkrooms will not impact the municipal sewer system or harm the environment. However, it is always better to be good neighbors and avoid putting anything down the drain that has the potential to harm.

    I was a registered environmental engineer with a specialty in photographic waste.
    ihordvoretskyi and blurrist like this.
  3. It is trivial to extract the silver from the fixer when the fixer is exhausted. Put it in a bottle with steel wool, and the silver will plate onto the iron of the steel wool. You can later decant the fixer (sans silver). Any silver recovery lab will gladly take your silver-plated steel wool.
  4. Hi, pretty much like Alan says. But probably the real reasons your teacher saves the fixer are 1) it can be reused a few times (when the silver
    concentration of the fixer reaches a certain level, then it should not be used anymore), and 2) there are municipal regulations in most
    places that restrict the concentration of silver being dumped to a sewer to very low concentrations. Even if you (or your school) is not
    regulated, your teacher may be sending the used fixer to some sort of silver recovery system or company.
  5. A little off topic, Kathyrn, but a fun demo in science (especially chemistry) is to take some diluted tincture of iodide and add a grain or two of sodium thiosulfate. Fun to watch the solution turn from reddish brown to clear in a few seconds.
  6. One consideration is oxygen. One part of treatment plants uses aerobic (oxygen using) bacteria to eat up some things. Chemicals that use up oxygen, such as developers, make it harder to keep the oxygen level up.
    Another is chlorine. As above with iodine, thiosulfate also reacts with chlorine, converting it to chloride ions. At the end of treatment, they put in enough chlorine to kill any left bacteria. Thiosulfate means that they need more chlorine. (You will also find thiosulfate in swim shampoo, for getting the chlorine out of your hair.)
    Both are more of a problem for large (or small) labs, and not so much for home or school.
    A minilab might have some gallons of each, and could dump it all at once. A large lab might have tens or hundreds of gallons.
    You can recover silver from fixer, but as far as I know, not in large enough quantities to sell to anyone.
  7. Both human waste and photo waste have an oxygen demand. They both take on oxygen as they age. Eventually this results in the waste becoming inert. The waste treatment plant must aerate to cause the plant’s effluent to go to completion. The plant must be sized to handle the load of the community. A big photo lab or food processing plant or industry discharging waste with oxygen demand could challenge the plant’s capacity. This is especially true in summer. Warm water has less ability to hold oxygen. If the plant is overwhelmed, they can’t stockpile the waste, so they must discharge it. If the effluent continues to take on oxygen it enters nearby waterways and competes with the aquatic life for oxygen. A fish kill or algae bloom results. Big photo labs that discharge lots of photo waste may need to pretreat their effluent to reduce oxygen demand.
    ihordvoretskyi and blurrist like this.
  8. Alan, I have to congratulate you, that is one of the best descriptions of the chemistry behind photo developing that is A) only 4 short paragraphs long B) easily understood by the lay person.
  9. Alan points out significant issues with treatment of photoprocessing effluent and clearly has in-depth knowledge of the issues. But lest
    people get worried about industry overwhelming the treatment plants, they should understand a few things about how the "system" works.
    If, in the U.S. at least, you decide to open your own photoprocessing lab, you won't be allowed to connect to a sewer system until a number
    of things happen. You will need to fill out paperwork describing characteristics of your proposed waste, including estimates of "BOD" and
    "COD," two measures of how much oxygen is needed to degrade the waste.

    If you are doing things right, you will most likely eventually get a "sewering permit" from the municipality which will specify the details of
    what you will be permitted to discharge, as well as the details of how this will be verified. Typically you are required to self-monitor, and for
    example, you might have to pull flow-proportioned samples periodically from a specially installed sewer-sampling point; these are then
    tested by a certified lab. Additionally, as part of the permit, representatives from the municipality will have the right to enter your facility without notice at any
    time to access the sampling point.

    If your effluent would overwhelm the treatment plant, or violate any of the municipal regulations, you will not be getting a permit and will
    not be allowed to connect to the sewer system. Part of the process is that you might be required to install your own pretreatment systems,
    but an alternative may be to pay for the municipality to do so. It used to be very common for municipalities to handle excess BOD and COD
    levels under a surcharge agreement.

    A lot of the regulations are a bit nutty, but finishers have to comply, regardless. Otherwise you could be disconnected, effectively shutting
    down your business. I don't know about the small users, or even schools, which is why I raised the question of whether the school is
    regulated (with respect to their photoprocessing effluent).
    ihordvoretskyi and blurrist like this.
  10. @ Eric Goldstein-- Thanks so much - I was Technical Manager for Eckerd Drugs, a Southeastern chain of drug stores. At its heyday, 2000 stores, now mostly absorbed by CVS. I built 7 giant photofinishing labs, each sized for 20,000 rolls of film developed and printed per day. I was forced to became knowledge in photo effluent and I was forced to pre-treat. We did silver recovery by every means possible and we recovered spent developers and reconstituted etc. Latter I was Technical Information Manager for Noritsu. Fixer and Bleach/fix is in my vanes, 55+ years and more.
    ihordvoretskyi likes this.
  11. Perhaps this could help you:

    The question I have is how many photo labs using chemicals are still in business?
  12. Fixer is reusable to a point of exhaustion, most developers are used as a "one shot", use once & discard, unless a large quantity of film is being developed in which case the developer can be replenished, more for economical reasons than anything else. Sounds like for your science project you're not going to be developing sizeable quantities of film, and by sizable, I mean dozens & dozens & dozens of rolls, so just follow as she recommends. Developer, once mixed, normally doesn't have quite as long a shelf life as does fixer, so there's really no point in keeping your developer if you're just doing a few rolls at a time. For the average consumer/amateur/hobbyist, most of the time, it's not practical to replenish developer, not that you can't, but you spend as much time and usually more money replenishing, than by just mixing a new batch of developer. When the fixer that I use is exhausted, out it goes, it's not worth my time and effort to try to replenish or reclaim silver from the fixer.
  13. [Mark] " When the fixer that I use is exhausted, out it goes, it's not worth my time and effort to try to replenish or reclaim
    silver from the fixer."

    Mark, are you quite sure? It sounds like you might do a pretty fair amont of developing. If so, you might want to look into a
    device called the Silver Magnet, a relatively cheap, low maintenance electrolytic recovery unit. The recoverable amount is
    roughly on a par with the US credit card company that advertises "cash back."
  14. I've looked into that very thing, and was very tempted. I do a fair amount of developing, but it goes in fits & spurts. I may do anywhere from 1 or 2, to 8 or 10 or 12 rolls, or 2 or 4 sheets to a dozen or two, along with wet prints, during any one session, but on the other hand... it might be 8, 10 or even 12 weeks or more before I do it again, and the fixer would in "recovery" for 6-12 months. I travel for work on an irregular basis, and have moved from Cali to Colorado, back to Cali, back to Colo. and then to N. Cali, then to Seattle and now back to Socal, so for me at least, it's not made much sense for me to go in that direction. I live San Diego, and when it heats up July thru mid October, & I'm away for weeks at a time, the fixer more often than not, doesn't hold up to storage. I've come home more than once, to what I though was a gallon of perfectly good fixer, used maybe a couple times, 3 or 4 rolls, kept in nice airtight amber glass bottles, in a cool shaded place, regardless of brand, being no good, so I end up having to mix new again anyway. I do think however, that, for students or hobbyists who are just starting or maybe doing a couple rolls a week, here and there, infrequently if you will, it might make a little more sense to toss it once it's exhausted, and then maybe later, they can decide about whether "to recover or not to recover!" (did I just say that?...jeez!...that was pretty sad!...) anyway, I looked at it on a cost/recovery/time basis, and it's just not for me, I'm not saying it bad, quite the contrary, it's just not for me, and as I creep up on retirement, I don't see myself going in that direction. I have enough trouble trying to shoehorn in time for my wife and kid's and grandkids, and painting the house & maintaining the yard, fixing the faucet, trimming the trees, taking the trash out, picking up after the dogs, trying to dig Cheerios out my grandson's nose, it goes on & on, you get the picture...anyway...Cheers Mr. C, I truly hope that keep up your enthusiasm for film as I have, it's my therapy, it's I what I put myself into, and it's great fun I hope that it is for you too!
  15. "Cheers Mr. C, I truly hope that keep up your enthusiasm for film as I have, it's my therapy, it's I what I put myself into, and it's great fun I
    hope that it is for you too!"

    Thanks mark, I became enamored with photography about the age of five, and I never outgrew it; it's been my only occupation since about
    1970. BTW if you ever bite the bullet on the "magnet," don't let the silver sit around too long; once it ages (loses most of its sulfite) you won't
    be successful electroplating. Silver loads vary a lot with films, but as an approximation you can probably recover silver worth about 2% of
    the original film cost, plus or minus a factor of 2x. (I oversaw the recovery of about half a million dollars per year back when it was 6-8
    $/troy oz; like Alan, we used about every sensible method.)
  16. The typical roll of 35mm black & white film contains about 0.008 Troy Ounces of silver. Let’s say that about half that remains on the film and the remainder, 0.004 Troy Ounces is dissolved in the fixer. We process 100 rolls and recover all the fixer contained in the fixer. Our prize will be 0.004 X 100 = 0.4 Troy. We send this off to a refiner and find the yield is about 0.2 Troy Ounce of 99.9% silver. The going rate is $20. We can gain 0.2 X 20 = $4 US dollars minus shipping, minus refining charge. That’s your gain for 100 typical rolls.
  17. Ok, I know I've reviving an old thread, but another of my threads has dipped into a problem that I've tried to solve for years and failed. I did relatively low amounts of developing and have maybe 3 gallons of spent fixer in the garage that I reused several times before I poured into these jugs. They've been sitting in my garage for decades because I can't take them to my local photo store anymore to safely dispose of the fixer (because the camera store is extinct in my area). For those few gallons of chemical, is there a safe way to dispose of it so that I won't hurt my pipes or my neighbors or the local treatment plant?

    I've been told about the bucket with steel wool and pour the fixer through the wool and put a flat piece on top of the bucket and wait for some amount of time trick. Is this valid science? I figure Alan can probably tell me (and some of the rest of you too). I've also been told that I might be able to use the system dentists use but I figure at this point they're probably all digital on their xrays these days anyway.

    Thanks. I'd like to get rid of this stuff before I die! ;)
  18. Dilute small amounts at a time with water until it's simply not fixer anymore. That can take a lot of water but it won't empty the town's water supply. If it's diluted enough, it will be much less acidic than vinegar which some people use to clean their plastic electric jugs, they then pour it down the sink with rinsing water used to rinse the jug.

    Clean your concrete driveway with the diluted fixer. It won't clean very effectively because you will be working with a greatly diluted mix, but after about twenty times, your driveway should be somewhat newer looking
  19. The steel wool trick does work-you will get silver "sludge" in the bottom around the steel wool and then you can decant off the solution and safely sink dispose of it.

    At $14/toz, you might need a fair bit of silver "sludge" to make it worth dealing with. If silver ever runs up to $40+/toz again, a metal buyer might take an interest in it.
  20. I think the steel wool needs to not have any oil on it, which will keep the solution away.

    Otherwise, electrolytic, with an actual voltage on the steel wool, will speed up the process.

    The electrochemical potential of iron and silver aren't so far apart, so it might be slow without help.

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