Also see https://solar.lowtechmagazine.com/2021/03/urban-fish-ponds-l...

The end of that article is kind of sad because it details the reasons these very effective low-tech sewage treatment methods are being phased out, and they are some of the same systemic problems that are preventing climate action worldwide: - low cost of fossil fuels (due to negative externalities) driving out sustainable alternatives - global speculation on real estate / urban sprawl - inadequate regulation of destructive activities

Everything will have to change for our civilization to continue in the face of the climate crisis, we must rethink every system our lifestyle relies upon, sewers included.