.. if the power is out long enough, the sewer systems will back up into people’s homes.
Depends on where you live and how the system works.
What we have learnt:
Problem 1: With power failures the pumps that moves water around stops. So your house may run out of water, meaning you cannot flush either.
Problem 2: With power outages the sewage farms also come to a standstill.
Problem 3: Depending on where you live ito height you can have it push back up due to pressure from areas higher up if the pipes lower than you are clogged due to insufficient water keeping the sludge moving / pumps stopped pumping it.
Or it is simple as your drain clogs due to insufficient water to flush the paper and solids down to the main sewer.
If the sludge does get to a point where it overflows the system, not much you can do in suburbia. The stench becomes unbelievable not to mention the flies if it takes too long to resolve.