Well yeah, but how do you communicate what is meant to be there and what not? Diapers, well it's obvious that that shouldn't be there. But ground up biological waste actually improves the functioning of water treatment stations (depending on the technology used). So now is a tea bag OK to grind up and flush? What if it's one of those newfangled plastic tea bags? Those are not OK but it's not obvious that they aren't (I wouldn't have known if one hadn't got stuck in my grinder...).

An interesting problem - improving on a system that is so behind the scenes that hardly anyone ever thinks about its functioning. To make changes to that, you need large scale social engineering techniques to implement those changes - a 'message of general interest' or two on TV isn't going to cut it.