[Kartographer]

You are right of course sewage treatment plant shut down can be as dangerous as water treatment plant shutdown. You are looking at any number of diseases with either. Most people have no idea of the complex systems behind both they just think water just 'magically' comes from the faucet and sewage just runs down the drain.

[Roos_Girl]

It’s not just a complete plant outage to worry about either. Gravity mains connect to pump stations. Power goes out and the pumps don’t pump, sewer backs up into the lines. Depending on how low your are I think it’s more likely that the lift station wet well will just overflow rather than back up all the way into a house. But, it’s nice to be prepared. :)