Caffiene is a very robust compound and passes intact through your digestive tract and through the treatment plant. A few years ago local agencies were hoping to use caffiene as a tracer when a sewage spill occured since instrumentation is incredibly sensitive to it. Problem was that there are relatively high background levels of caffiene through out the sound. Seems people in Seattle like there coffee. The idea of using caffiene as a tracer was abandoned because we souldn't really tell anything from the amount of caffiene already out there.
I have brought up estrogen, estrogen mimicers and endocrine disrupting compounds in previous posts. There is some disturbing information coming out through some recent studies. Some widely used industrial chemicals that were previously thought to be benign have been found to disrupt very sensitive biological systems.
Keep in mind that treatment plants are not some magical voodoo mystery machines. Some organic compounds can be digested and broken down, however some are not. The unfortunate fact is physics laws still apply and what goes in eventually goes out, either as a liquid in effluent or as a solid. Sorry, but that's the facts. Everyone must realize that they themselves have a huge impact on the water quality in the sound simply by what they send down the drain. We are intimately connected to the sound whether we admit it or not.
Steve