Maybe we should rethink wastewater streams for selective recycling: stormwater, graywater, blackwater, and yellowwater. Perhaps the latter two should be recycled where possible and then residual wastes close-loop incinerated to prevent leeching any sort of biologically-active molecules or pathogens into the environment.
The quantity of drugs in the waste stream is surprising. For example: I take 1000 mg daily of metformin. Although I have (of course) never measured it, a person produces 100 to 250 g/day of fecal matter. This is 75% water, so reasonably my excreta, on a dry basis, is up to 4% metformin(!). Metformin is largely excreted and breaks down in the environment only slowly, so it would contribute significantly to the nitrogen figure for waste-derived fertilizer.
Wikipedia says this:
"Metformin and its major transformation product guanylurea are present in wastewater treatment plant effluents and regularly detected in surface waters. Guanylurea concentrations above 200 μg/L have been measured in the German river Erpe, which are amongst the highest reported for pharmaceutical transformation products in aquatic environments."
