The bleach usually used contains copper II and chromium VI. Both are quite poisonous, but the small quantities and great dilution in the sewage system generally make them innocuous. Copper sulfate is often used as a root inhibitor in sewage systems, and is generally tolerated well both chemically and legally. Some jurisdictions may be a bit more fussy about dichromates, which are classed as carcinogens. Most will allow disposal of small quantities, such as what you have, down the drain, but some may not. If you are one of the rare, unlucky ones, you can convert them into chromium III (like chrome oxide), which is safe.