All the
local material I have been able to find on the internet indicates that if you intend to deal with a waste disposal service, it must be a private, for profit one (no doubt for a fee).
Here is a link with information about many of those for profit entities:
http://www.hazwastebc.com/Hazardous_Waste_Receiver-Processor_Capabilities.html
This link from the regional district's site ("Metro Vancouver") provides a "Code of Practice for Photographic Imaging Operations (which) sets out the requirements for managing Non-Domestic Waste discharged directly or indirectly from a Photographic Imaging Operation into a Sewer or a Sewage Facility.".
Dead Link Removed
This is, of course, oriented toward businesses. I find it interesting, however, that it seems to only restrict 'down-the-drain' disposal of "Silver-Rich Solutions".
Those are defined as: "“Silver-Rich Solution” is a solution containing sufficient silver such that effective recovery can be done either on-site or off-site. Within photographic processing facilities, such solutions include, but are not limited to, fix and bleach-fix solutions, stabilizers, low replenished (low-flow) washes, and all functionally-similar solutions. It does not include low silver concentration solutions such as used developers, bleaches, stop baths, pre-bleaches, and stabilizers following washes and wash waters."
From this I infer that, as far as Metro Vancouver is concerned,
commercial photographic labs may simply dump into the sewer system "
used developers, bleaches, stop baths, pre-bleaches, and stabilizers following washes and wash waters."
Personally, I would phone Metro Vancouver with information about the quantities you have in hand
EDIT: Emphasis added