I line a strainer with paper towel and drain the water through that,
then dispose of the papertowel into the garbage. It should NOT go
down the drain as it is silica with metal oxides, etc. and is like
putting sand down the drain. Though a small amount may do no harm, a
bunch or continual amount can build up and plug the drain. This then
causes the need for a drain guy to roto root the pipes, at your
cost, and according to Murphy’s Law this will happen during off hours
and cost you even more.