Science Buddies: "Ask an Expert"

I want to know protocols/guidelines for the safe disposal of Colloidal Silver 1 ml (500ppm) solution.
This solution is going to be used to study survival of Daphnia Magna in fresh water in a home setting. Several volume dilutions of the colloidal Silver will be prepared using 1 ml of the concentrated solution. Please include reference sources for the above questions.

https://www.sigmaaldrich.com/MSDS/MSDS/ ... Flang%3Den

Here is the SDS for silver particles in water.

It recommends having a 'licensed disposal company' get rid of waste, but they say the same for salt water (https://www.sigmaaldrich.com/MSDS/MSDS/ ... Flang%3Den).
My impression is that means it is non hazardous and can go down a drain or outside with little or no environmental harm.