safe disposal of chemicals

Hi. I just bought a house in the woods. The garage is a separate
building, and I intend to set up a small metalworking shop to augment
my woodworking -- I just graduated from school where I fell in love
with metalsmithing while being a furniture major ... I especially love
making small vessels & objects. The main problem is that there's no
running water in the space, and no drainage pipes leading to my septic
tank.

The chemicals I use are silver, copper & nickel pickles, acid etching
chems, patinas, and sometimes photography chemicals.

Without spending a lot of $$, I figure I can set up a sink and feed it
with a gardening hose -- I can do this easily right outside the
garage's back door. But then I need to catch the runoff and dispose
of it somehow. I don't really want to introduce this stuff into my
septic tank, and feel uncomfortable with dumping it onto my hillside,
even if I were to build a greywater system. I suppose I can dispose
of it at the dump, but I'm lazy and would like to avoid that!!!

Of course the long term solution would be to get a separate septic
tank installed, or get a greywater sink that has a built-in filter,
but that's going to take me a while to afford.

Meanwhile, does anyone out there have similar circumstances? How do
you deal with it? Does anyone know for sure the relative toxicity of
the chems, and if neutralizing them with baking soda is enough to make
it safe for a greywater system? I read on a previous thread about a
woman who uses Spa Up (spa/pool chemical) instead of pickle -- is it
really safer? Does it work for all metals? As with my woodworking, I
want my metalworking to be as "green" as possible.

Any comments on this issue would be appreciated!
Thanks!
lisau