... "Load a fixer.."?
Then, "2 to 0.5 grams"? refers to the amount of silver ... where? Removed from each (size?) print? Or contained in "x" amount of working?/ saturated? fixer?
It's the amount of silver that 1 Litre of fixer solution can hold without becoming exhausted. There are only 2 things that kill fixer, first is the silver load, second is the carryover from other solutions.
As a fixer solution removes more and more silver from the film or paper, it holds that in solution, making the fixer itself less and less able to remove more silver from the film or paper. Rapid fixers at film strength can hold the most at 8g/L, Hypo at paper strength when used with FB papers can hold the least at .5g/L. This means that if you have an electronic silver recovery system that doesn't harm the fixer, the fixer can continue to remove silver until carryover from other solutions makes it too weak to continue. The other way to resolve this is replenishment, if you know that 1 roll of film adds 10% of the silver capacity and you replace 10% of the solution with fresh, then you can hold the fixer near exhaustion without reaching exhaustion for an extended period of time, this also takes care of the problem of carryover. It also means that your throwing away small amounts of partly loaded fixer often, rather then large amounts occasionally.
If you do 100 rolls a year, and use replenishment so that your using effectively 100ml per roll, then at the end of a year you have used 10L of fixer, about 2½ gallons for the Americans. That's a small enough load that it's an easy trip to the Hazmat depot for disposal. However, when you wash your film then some silver also goes into the wash water, so that should also be saved or treated before being sent down the drain, and for that one of the silver filtering systems is about the only real solution. The amount of silver per L of wash water is probably insignificant. If your using a silver recovery filter on your drain, then you might as well dump the fixer as well.
With all the anti-film hype these days, I've never heard reports of there being major environmental impact from photographic solutions, even though between 1900 and 2000 they were used extensively. There have been reports of septic systems being harmed in that the silver in large amounts of fixer killed the bacteria, but they can usually be pumped and restarted.
I have heard of there being major environmental impact from the chemicals used in the manufacture of electronics, so the digital idea that you must replace your old camera with a new one every 18 months, probably has much more environmental impact, then a little bit of fixer dumped down the drain now and then.
Probably the best though for silver recovery, there are other things that might contain silver that get washed down drains, is at the point of treatment. For example a silver filter at the point where grey water exits the building on the way to the septic tank, rather then the drain for the darkroom, for municipal systems too, removing any silver at the point where the sewage enters the facility, rather then the point where it is generated. Heck the slaves of the folks on snob hill polishing the silverware generates silver in the rinse water.