I still feel confused how big a sewershed is relative to a city
A sewershed can vary dramatically in size: it’s the area that drains to some collection point (generally a treatment plant) and different cities are laid out differently. I’m most familiar with Boston (after refreshing the MWRA Biobot Tracker intently during COVID-19) and here the main plant serves ~2M people divided between the North and South systems:
Some other cities have much smaller plants (and so smaller sewersheds), a few have larger ones.
We’re not sure yet about the effect of size. It’s possible that small ones are better because the waste is ‘fresher’ and you spend fewer of your observations (sequencing reads) on bacteria that replicates in the sewer. Or it’s possible that larger ones are better because they can support more observations (deeper sequencing).
A sewershed can vary dramatically in size: it’s the area that drains to some collection point (generally a treatment plant) and different cities are laid out differently. I’m most familiar with Boston (after refreshing the MWRA Biobot Tracker intently during COVID-19) and here the main plant serves ~2M people divided between the North and South systems:
Some other cities have much smaller plants (and so smaller sewersheds), a few have larger ones.
We’re not sure yet about the effect of size. It’s possible that small ones are better because the waste is ‘fresher’ and you spend fewer of your observations (sequencing reads) on bacteria that replicates in the sewer. Or it’s possible that larger ones are better because they can support more observations (deeper sequencing).
Nice. You’re such a fast writer! Very helpful, thank you!
It helps that I’m writing about stuff we’ve discussed internally a lot! Thanks for the good questions!