Welcome to India, a BBC TV programme, shows people making money by sweeping dirt on the roads of a jewellery district in Colcuta and recovering the gold. (Indian housewives have a staggering amount of physical gold.)
When those sweepings are running thin they go into the drains to gather sludge. Gold from jeweller's bodies and on the floors get washed into the drains. This sludge requires a lot of processing to get the gold, so the sludge is sold to a business with the man-power to do it.
They need to grind and dry the sludge. They then slowly wash it over ribbed troughs - the gold stays in the ribs while the dirt washes over. The gold-rich sludge is processed with mercury, glass, soda, and ash. This is melted in a crucible, to give you a gold / silver / mercury blob, which you then process with acid to get gold.
Later I'll put up some short clips of the video showing the various processes because my description isn't good and the programmes are no longer available online. But here's the BBC page for it. (http://www.bbc.co.uk/programmes/b01n8278)
If you don't mind travelling to Ghana you could surely do better than they're doing in Accra - Here's a snippet from a UK TV programme about the e-waste dump in Agbogbloshie. It's pretty depressing. There's no kind of sensible plan to recovering useful stuff. Seeing a boy smashing polyester / polystyrene capacitors off an old PCB with a rock is just grim. I guess by this point you just treat it the ground like ore - dig it up and process it.
(http://videobam.com/rcEUM) (Apologies for the awful video host. Any suggestions?) Here's a link to the original programme (http://www.bbc.co.uk/programmes/b00sch78)