Take the drugs back to the Pharmacy so they can dispose of them properly.   How hard can it be to do this?   Almost every time I do it I get a smile and "thanks!" from the Pharmacist.   This is one of the best services offered here and is effectively part of your dispensing fee so just do it!

It's virtually impossible to remove all the chemicals from the water system because there are so many different ones, and so that means that your drinking water contains traces of all this stuff EVEN just from sewage, let alone people dumping unused drugs.   The thing is that most prescriptions for painkillers don't get close to completely used, and so returning the unused drugs makes a difference.