The problem with trying to dry an activated carbon filter is that you can't. It may appear dry externally, but internally it will retain moisture for a very long time. Regardless, IMO it's better to remove the filter from the housing, rinse it well with tap water and let it air dry as best you can. I really don't like leaving the cartridge sitting in the cannister full of water. The next time you use it, flush it well by running water through it for a few minutes first. This is about the best you can do. Only use the water in the pre-boil phase of brewing. The boil should kill anything that happens to get into the kettle. I've been using this method for years with the same cartridge without problems.