Replace "netflix" with "health care" and re-read the post. Th point is it's stupid to pay for something 3 times over but thats how (American) health care is.
Every treatment plant in the country is already collecting samples of wastewater as it enters and leaves the plant as they have to take certain measurements every day to show compliance. To my knowledge, there is no way to identify/track individuals based on wastewater. There is a government database of everyone's license plate.
The primary purpose of wastewater treatment is biological material and nutrient removal, primarily nitrogen. Check out the wikipedia page for more details, I'm a biologist, not a chemist. https://en.wikipedia.org/wiki/Wastewater_treatment
So this is actually my industry - Wastewater Based Epidemiology or WBE. It is very anonymous. There is no way to pick out one person's identity from the waste stream. What we get is a about 100mL of blend from 24 hour's worth of shit water passing into the treatment plant. A tiny treatment plant is processing 100,000 gallons per day, while a top 10 plant is processing > 100 Million gallons per day.
Replace "netflix" with "health care" and re-read the post. Th point is it's stupid to pay for something 3 times over but thats how (American) health care is.