In lecture, we briefly touched on how antibiotics can be 'salvaged' from urine, and Maggie's post "Pollution and Antibiotics" notes the release of antibiotics into the environment.
The United States Geological Survey (USGS) has done studies (click here for one example) describing organic compounds, which include antibiotics, which were found in water that has been treated in U.S. wastewater treatment facilities and is subsequently deemed 'potable.'
I have also heard that researchers at UC Merced are examining surface waters of the Sierra Nevada for evidence of pharmaceutical contamination. This might occur, for example, around upscale backpacking hotspots (like the High Sierra Camps or Yosemite Valley in Yosemite National Park) where large numbers of people using caffeine, male 'enhancements,' birth control medications, pain relievers, and antibiotics would be excreting large amounts into the watershed. The Sierra watersheds are the source of all of the drinking water for San Francisco and a number of the other Bay Area cities, as well as for the irrigation and drinking in the Central Valley and southern California.
In light of this information, I am reflecting on the two weeks I spent backpacking in the upper Tuolumne River watershed of Yosemite National Park, all the while completing a course of antibiotics (Doxycycline) to treat my Lyme disease.