Labs are required to treat waste effluent to keep silver out of the environment.
That is correct. I don't try to recover my waste. I put into a disposal barrel that I got from SafetyKleen and whenever it's full, they come take it away and give me a new empty one. It does cost money, but it saves me more time than what I'd get out of it if I tried to recover it, and I just build that cost into the cost of processing a roll. I replenish my fix so my per roll waste is pretty low.
It's been that way in the US, lab effluents being regulated, for about 35+ years now. So nothing too new; just not well-known to people outside of commercial labs.
Something else not well-known is how nutty some of the regulated standards are. In the US each municipality makes its own laws about what will be accepted into its own "POTW," the publicly owned treatment works, aka "the sewer." The outfit where I worked once owned a large chain of one-hour labs. I was not part of that division but did see some of the effluent regulations. And I like to grouse about it once in while, which is what this post is.
Since Adrian has brought up the situation of his lab, which I presume is also in Petaluma, California, I looked online for their effluent limits. There is a page giving "discharge limits" for silver at 0.10 mg/L, that is, milligrams of silver per liter. To put this in perspective it is roughly the same ratio as if someone had tried to control the population of metro Los Angeles, about 13 million people, to within a bit over one person. It's an unusually stringent limit. (I've designed some large-lab effluent control systems that ran below 0.20 mg/L silver so I know how difficult this is.)
The Petaluma web site gives some other discharge limits: arsenic, at 0.20 mg/L, can be discharged at twice the limit of silver. Cyanide is similar, being limited to 0.26 mg/L. One might think that oh, silver DOES need to be limited that stringently, but... if one looks at EPA drinking water standards, silver is treated as a secondary pollutant with a guideline limit of 0.1 mg/L. In other words, the Petaluma discharge limit for silver is the same as the EPA drinking water standard! Imagine if they treated ALL pollutants the same, essentially you would not be able to discharge anything to the sewer unless it was safe to drink.
But back to photo processing - what does it take to meet a silver limit of 0.10 mg/L? Well, I would say it's not achievable by a normal photographer. Even taking fixer to a hazardous waste facility is not enough. Let me use C-41 processing as an example. But first let me say that effluent regulations don't allow dilution as a means of controlling pollution. So what IS dilution in the case of C-41 processing? In my view, any wash water usage beyond that specified in Kodak's Z-131 process manual can be seen as dilution. If one uses a single wash tank (as opposed to multi-stage washing with counter-current water flow) Z-131 specs about 3.3 liters of water per nominal roll.
So how does this wash water limit affect silver concentration in the effluent? Well the way that silver gets into wash water is by being carried over from a fix tank - the "dirty" film gets some of the wash water dirty. Z-131 lists some typical carry-out amounts for a processor with "efficient squeegees;" it's about 7 ml per roll. Now when one processes by hand, or in a Jobo processor for that matter, they are not generally using a squeegee after the fixer. I would estimate that the fixer carryover is roughly double the squeegeed rate, perhaps 14 ml per roll. This is disregarding what the reel carries over. Let's say that you use your fixer lightly, only letting the silver concentration rise to about 1/2 g/l. Now there is enough information to calculate the silver concentration in the wash water. It's about 2 mg/l, roughly 20 times higher than the allowable discharge limit to the Petaluma sewer system. (The calculation is to take the total amount of silver carried over, about 1/2 gram/1000 ml x 14 ml, and then divide that by the total wash water, about 3.3 liters. This calculation gives GRAMS of silver per, remember that the discharge limits are in milligrams, so multiply by 1,000.)
Thanks for bearing with me on my little rant. Perhaps it'll help explain part of the reason why there are so few smaller labs around nowadays. The expertise needed to deal with these issues can be costly for a small operation. This sort of thing is a major reason why so-called washless systems were developed. They didn't need a permit cuz there was no sewer connection. The low wash volume made it feasible to have all the waste hauled offsite by a licensed waste disposal outfit.
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